Karst is a landscape formed where rock dissolves in water. The U.S. Geological Survey groups two families of soluble rock:

Where is gypsum found in western Oklahoma?

The Cottonwood soil series formed in material weathered from massive gypsum, mostly alabaster, of the Permian-age Blaine Formation. It occurs in southwestern Oklahoma and northwest Texas. In these soils:

Gypsum karst and sinkholes: What about limestone and dolomite?

The Oklahoma Geological Survey notes that marine carbonate rocks of Late Cambrian and Ordovician age underlie most of the state, and that carbonates reach more than 8,000 feet thick near the Southern Oklahoma Aulacogen, described as part of a failed triple junction, an ancient rift that stopped developing.

What are the field signs of karst?

These are the kinds of observations that prompt a closer look for voids:

Gypsum karst and sinkholes: What are the limits of the maps?

The USGS karst map shows where soluble rock occurs, but it does not rate hazards such as sinkhole collapse. It is a first approximation intended to guide more detailed study of specific areas.

Gypsum karst and sinkholes: What should repairs consider on soluble rock?

Because water drives dissolution, controlling surface drainage near a suspected void is a common first concern; see surface drainage and grading. Repair approaches are described on void and compaction grouting and working with engineers.

Karst is ground shaped by rock that dissolves in water, such as gypsum, salt, limestone and dolomite. Dissolution can leave caves and voids, and the ground above can sag or collapse into sinkholes.

Does Oklahoma have gypsum near the surface?

Yes. In parts of western and southwestern Oklahoma, soils such as Cottonwood sit only a few inches above massive gypsum of the Permian Blaine Formation.

Gypsum karst and sinkholes: Where can I report a sinkhole in Oklahoma?

The Oklahoma Geological Survey provides an online sinkhole report form through its FAQ page.

Gypsum karst and sinkholes: Do sinkhole hazard maps show which houses are at risk?

No. The national USGS karst map shows where soluble rocks occur, but it does not rate sinkhole collapse hazard for specific sites; it is meant to guide more detailed local study.

Under-slab plumbing leaks: How does a leak move a foundation?

Expansive clay swells when water enters and shrinks when it dries. Most moisture-driven movement starts at the outer walls, but water that reaches the soil under the middle of a house, including from plumbing leaks, can cause movement in the interior too.

What are the warning signs of a slab leak?

A rising area in the floor, with cracks spreading from it (interior floor hump); Unexplained high water use. The EPA notes that a family of four using more than 12,000 gallons a month in winter probably has serious leaks.

Under-slab plumbing leaks: What simple leak checks does EPA guidance suggest?

Household leaks are common: the EPA estimates that about 9% of homes have leaks wasting 50 gallons or more a day, and that the average household's leaks waste more than 9,300 gallons a year.

Under-slab plumbing leaks: Why does the order of work matter?

Engineering guidance on expansive soils puts dealing with the causes of uneven moisture first, including repairing plumbing leaks and revising site drainage.

Can a plumbing leak cause foundation problems?

Yes. Leaking pipes add water to the soil under a house. On expansive clay that water can make the soil swell and lift part of the slab, and engineering sources list plumbing leaks among the causes of uneven moisture under foundations.

Under-slab plumbing leaks: How can I check for a hidden water leak?

The EPA suggests reading the water meter, using no water for two hours, and reading it again. If the reading changed, there is likely a leak.

Is a high water bill a sign of a slab leak?

It can be. The EPA notes that a family of four using more than 12,000 gallons a month in winter probably has a serious leak somewhere in the system.

Under-slab plumbing leaks: Should a leak be fixed before foundation repair?

Engineering guidance on expansive soils lists repairing plumbing leaks among the first steps, because leveling a foundation without removing the source of extra moisture can produce only temporary results.

How do trees affect a foundation?

Oklahoma's expansive clays swell when wet and shrink when dry (see shrink-swell and the active zone). A tree adds a strong, local drying force to that cycle.

OSU Extension describes tree roots as mostly shallow and wide:

Trees and roots: Which Oklahoma tree species matter?

OSU Extension's tree selection guide describes root and growth traits for common Oklahoma trees:

How far from a house should trees be planted?

The City of Oklahoma City's planting guide says medium and large trees should be planted no closer than 30 feet to buildings or structures; The same guide allows trees listed as suitable near water lines at 5 feet from lines 4 inches in diameter, or 10 feet from larger lines; OSU Extension advises planting at least half the mature canopy width away from the home, and keeping fast-growing or weak-wooded trees well away from buildings.

Trees and roots: What signs suggest a tree is involved?

Field clues that point toward a tree include settlement on the side of the house nearest the tree, cracks that open toward it (for example stair-step cracks wider at the top), and soil pulled away from the foundation near the root zone.

Trees and roots: What options do people consider?

Root barriers and moisture control. A vertical barrier between tree and house, or steady soil moisture, aims to limit drying under the footing. See root barriers and moisture control; Tree management or removal. See tree management; Piers.

Do tree roots push foundations and crack them?

Usually the bigger effect is drying. Roots draw water out of clay soil, the clay shrinks, and the footing on that side can settle. Many roots reach a foundation and then grow along it rather than under it.

Trees and roots: How far from my house should a tree be planted in Oklahoma?

Oklahoma City's planting guide says medium and large trees should be no closer than 30 feet to buildings. OSU Extension says to plant at least half the tree's mature canopy width away from the home.

Trees and roots: Can cutting down a big tree near my house cause problems?

It can. Once the tree stops drawing water, moisture slowly returns to the clay, which can swell and push the ground up (heave). Building guidance warns this swelling can damage nearby foundations, especially on clay.

How far do tree roots spread?

OSU Extension says roots often spread up to three times the canopy width, and up to five times in shallow soils over clay. Most absorbing roots sit in the top 24 inches of soil.

What is the Oklahoma Mesonet?

The Mesonet was officially commissioned on January 1, 1994, and is a joint project of the University of Oklahoma and Oklahoma State University, operated by the Oklahoma Climatological Survey. The current network has 120 stations.

What soil moisture data does it report?

A few practical notes from the sources: - Soil moisture can't be measured when the ground is frozen, so winter maps can have gaps. - The rate at which soil moisture falls reflects how hot and dry the air is; it drops faster in hot, dry spells. - Comparing depths after a rain shows how deep the water soaked in.

How does Mesonet data connect to foundations?

Expansive clay swells when it gets wet and shrinks when it dries, and uneven moisture under a slab causes differential movement, meaning one part of the house moves more than another.

What is the Oklahoma Mesonet?

It is a statewide network of 120 automated weather stations run jointly by the University of Oklahoma and Oklahoma State University. Stations are in all 77 counties, about 18 miles apart on average.

How deep does the Mesonet measure soil moisture?

Most sites have sensors at 2, 4, 10 and 24 inches (5, 10, 25 and 60 cm) below the surface.

Using Mesonet data: What does the fractional water index mean?

It is a 0-to-1 scale of soil wetness. A value near 0 means the soil is about as dry as the sensor can read, and a value near 1 means it is about as wet as the sensor can read.

Does Mesonet soil moisture tell me how deep my foundation soil is drying?

Only partly. The deepest standard sensor is about 2 feet down, while seasonal moisture change under houses on clay can extend many feet deeper, so the readings show the trend rather than conditions at pier depth.

What does the shale weathering profile look like?

From the surface down, a typical shale profile looks like this:

Shale weathering and bearing: Where does the active zone sit?

The active zone, the depth of soil whose moisture changes seasonally, mostly lies in the clay and weathered layers. At four studied Houston clay sites it was about 8–10 feet before the 2011 drought and 10–12 feet during it.

Why does bearing depth matter for each pier type?

Steel push piers are driven until they reach a layer that resists the load; the depth where that happens is the bearing depth; Pressed concrete piles rely on a mix of end bearing and side friction, so stiff, dry clay can produce resistance at shallower depth during drought; Helical piers are screwed in, and installation torque is used to estimate capacity.

What is a bearing stratum?

It is the soil or rock layer strong enough to carry a foundation's load without settling. For repair piers, it is the layer the pier is driven or drilled down to.

Shale weathering and bearing: How deep do foundation piers go in Tulsa?

Oklahoma steel push pier installation records show typical depths of about 8 to 16 feet, with a median of about 12 feet in Tulsa. Depth at any one house depends on its soil and rock.

Shale weathering and bearing: Why does it matter if a pier stops in dry clay?

Clay within the active zone changes volume with moisture. A pier that reaches resistance in stiff, dry clay during a drought may still be in soil that swells or softens when it rewets.

Shale weathering and bearing: What is the difference between soft and hard rock in soil surveys?

USDA soil descriptions call the top of soft, weathered rock that can still be dug a paralithic contact, and the top of hard rock a lithic contact.

Erosion, creeks and slopes: How does water take soil away?

Flood-plain soils show how active these settings are. Port soils, on narrow flood plains in central Oklahoma, flood occasionally or frequently for very brief periods during March to October.

Erosion, creeks and slopes: What are other warning signs?

Besides exposed slab edges and leaning walls or trees, sign pages on this site cover a sudden depression or sinkhole, which can mark underground soil loss, and water ponding near the foundation, which shows where runoff collects.

Erosion, creeks and slopes: How are these problems repaired?

Because steep slopes, bare ground and heavy rain drive erosion, repair options focus on the water and the slope as well as the house. They are described on slope and erosion stabilization and drainage solutions.

Guides: every question answered

359 questions with short answers. Each links to the full, sourced explanation.

Are there gypsum sinkholes in western Oklahoma?

Yes, in places. Gypsum near the surface can dissolve in groundwater, leaving voids that let the ground above sag or collapse.

What is karst?: Karst is a landscape formed where rock dissolves in water. The U.S. Geological Survey groups two families of soluble rock:
Where is gypsum found in western Oklahoma?: The Cottonwood soil series formed in material weathered from massive gypsum, mostly alabaster, of the Permian-age Blaine Formation. It occurs in southwestern Oklahoma and northwest Texas. In these soils:
Gypsum karst and sinkholes: What about limestone and dolomite?: The Oklahoma Geological Survey notes that marine carbonate rocks of Late Cambrian and Ordovician age underlie most of the state, and that carbonates reach more than 8,000 feet thick near the Southern Oklahoma Aulacogen, described as part of a failed triple junction, an ancient rift that stopped developing.
What are the field signs of karst?: These are the kinds of observations that prompt a closer look for voids:
Gypsum karst and sinkholes: What are the limits of the maps?: The USGS karst map shows where soluble rock occurs, but it does not rate hazards such as sinkhole collapse. It is a first approximation intended to guide more detailed study of specific areas.
Gypsum karst and sinkholes: What should repairs consider on soluble rock?: Because water drives dissolution, controlling surface drainage near a suspected void is a common first concern; see surface drainage and grading. Repair approaches are described on void and compaction grouting and working with engineers.
What is karst?: Karst is ground shaped by rock that dissolves in water, such as gypsum, salt, limestone and dolomite. Dissolution can leave caves and voids, and the ground above can sag or collapse into sinkholes.
Does Oklahoma have gypsum near the surface?: Yes. In parts of western and southwestern Oklahoma, soils such as Cottonwood sit only a few inches above massive gypsum of the Permian Blaine Formation.
Gypsum karst and sinkholes: Where can I report a sinkhole in Oklahoma?: The Oklahoma Geological Survey provides an online sinkhole report form through its FAQ page.
Gypsum karst and sinkholes: Do sinkhole hazard maps show which houses are at risk?: No. The national USGS karst map shows where soluble rocks occur, but it does not rate sinkhole collapse hazard for specific sites; it is meant to guide more detailed local study.

Can an under-slab plumbing leak move an Oklahoma foundation?

Yes. A leak under a slab can make expansive clay swell and lift the floor or soften and wash out looser soil, so the leak must be fixed for a lasting repair.

Under-slab plumbing leaks: How does a leak move a foundation?: Expansive clay swells when water enters and shrinks when it dries. Most moisture-driven movement starts at the outer walls, but water that reaches the soil under the middle of a house, including from plumbing leaks, can cause movement in the interior too.
What are the warning signs of a slab leak?: A rising area in the floor, with cracks spreading from it (interior floor hump); Unexplained high water use. The EPA notes that a family of four using more than 12,000 gallons a month in winter probably has serious leaks.
Under-slab plumbing leaks: What simple leak checks does EPA guidance suggest?: Household leaks are common: the EPA estimates that about 9% of homes have leaks wasting 50 gallons or more a day, and that the average household's leaks waste more than 9,300 gallons a year.
Under-slab plumbing leaks: Why does the order of work matter?: Engineering guidance on expansive soils puts dealing with the causes of uneven moisture first, including repairing plumbing leaks and revising site drainage.
Can a plumbing leak cause foundation problems?: Yes. Leaking pipes add water to the soil under a house. On expansive clay that water can make the soil swell and lift part of the slab, and engineering sources list plumbing leaks among the causes of uneven moisture under foundations.
Under-slab plumbing leaks: How can I check for a hidden water leak?: The EPA suggests reading the water meter, using no water for two hours, and reading it again. If the reading changed, there is likely a leak.
Is a high water bill a sign of a slab leak?: It can be. The EPA notes that a family of four using more than 12,000 gallons a month in winter probably has a serious leak somewhere in the system.
Under-slab plumbing leaks: Should a leak be fixed before foundation repair?: Engineering guidance on expansive soils lists repairing plumbing leaks among the first steps, because leveling a foundation without removing the source of extra moisture can produce only temporary results.

Can trees damage a foundation in Oklahoma clay soil?

Large trees rarely push a foundation. They mainly cause damage by drawing water from clay, which shrinks and lets the nearby part of the house settle.

How do trees affect a foundation?: Oklahoma's expansive clays swell when wet and shrink when dry (see shrink-swell and the active zone). A tree adds a strong, local drying force to that cycle.
Where are the roots?: OSU Extension describes tree roots as mostly shallow and wide:
Trees and roots: Which Oklahoma tree species matter?: OSU Extension's tree selection guide describes root and growth traits for common Oklahoma trees:
How far from a house should trees be planted?: The City of Oklahoma City's planting guide says medium and large trees should be planted no closer than 30 feet to buildings or structures; The same guide allows trees listed as suitable near water lines at 5 feet from lines 4 inches in diameter, or 10 feet from larger lines; OSU Extension advises planting at least half the mature canopy width away from the home, and keeping fast-growing or weak-wooded trees well away from buildings.
Trees and roots: What signs suggest a tree is involved?: Field clues that point toward a tree include settlement on the side of the house nearest the tree, cracks that open toward it (for example stair-step cracks wider at the top), and soil pulled away from the foundation near the root zone.
Trees and roots: What options do people consider?: Root barriers and moisture control. A vertical barrier between tree and house, or steady soil moisture, aims to limit drying under the footing. See root barriers and moisture control; Tree management or removal. See tree management; Piers.
Do tree roots push foundations and crack them?: Usually the bigger effect is drying. Roots draw water out of clay soil, the clay shrinks, and the footing on that side can settle. Many roots reach a foundation and then grow along it rather than under it.
Trees and roots: How far from my house should a tree be planted in Oklahoma?: Oklahoma City's planting guide says medium and large trees should be no closer than 30 feet to buildings. OSU Extension says to plant at least half the tree's mature canopy width away from the home.
Trees and roots: Can cutting down a big tree near my house cause problems?: It can. Once the tree stops drawing water, moisture slowly returns to the clay, which can swell and push the ground up (heave). Building guidance warns this swelling can damage nearby foundations, especially on clay.
How far do tree roots spread?: OSU Extension says roots often spread up to three times the canopy width, and up to five times in shallow soils over clay. Most absorbing roots sit in the top 24 inches of soil.

How can Oklahoma Mesonet soil moisture data explain foundations?

The Oklahoma Mesonet is a free statewide network reporting soil moisture. Its shallow readings show whether ground is drier or wetter than usual, as trends.

What is the Oklahoma Mesonet?: The Mesonet was officially commissioned on January 1, 1994, and is a joint project of the University of Oklahoma and Oklahoma State University, operated by the Oklahoma Climatological Survey. The current network has 120 stations.
What soil moisture data does it report?: A few practical notes from the sources: - Soil moisture can't be measured when the ground is frozen, so winter maps can have gaps. - The rate at which soil moisture falls reflects how hot and dry the air is; it drops faster in hot, dry spells. - Comparing depths after a rain shows how deep the water soaked in.
How does Mesonet data connect to foundations?: Expansive clay swells when it gets wet and shrinks when it dries, and uneven moisture under a slab causes differential movement, meaning one part of the house moves more than another.
What is the Oklahoma Mesonet?: It is a statewide network of 120 automated weather stations run jointly by the University of Oklahoma and Oklahoma State University. Stations are in all 77 counties, about 18 miles apart on average.
How deep does the Mesonet measure soil moisture?: Most sites have sensors at 2, 4, 10 and 24 inches (5, 10, 25 and 60 cm) below the surface.
Using Mesonet data: What does the fractional water index mean?: It is a 0-to-1 scale of soil wetness. A value near 0 means the soil is about as dry as the sensor can read, and a value near 1 means it is about as wet as the sensor can read.
Does Mesonet soil moisture tell me how deep my foundation soil is drying?: Only partly. The deepest standard sensor is about 2 feet down, while seasonal moisture change under houses on clay can extend many feet deeper, so the readings show the trend rather than conditions at pier depth.

How deep do foundation piers need to go in Oklahoma shale?

Shale weathers top-down into clay; piers aim for firmer material below the shrink-swell layers, and Oklahoma push pier records run about 8 to 16 feet.

What does the shale weathering profile look like?: From the surface down, a typical shale profile looks like this:
Shale weathering and bearing: Where does the active zone sit?: The active zone, the depth of soil whose moisture changes seasonally, mostly lies in the clay and weathered layers. At four studied Houston clay sites it was about 8–10 feet before the 2011 drought and 10–12 feet during it.
Why does bearing depth matter for each pier type?: Steel push piers are driven until they reach a layer that resists the load; the depth where that happens is the bearing depth; Pressed concrete piles rely on a mix of end bearing and side friction, so stiff, dry clay can produce resistance at shallower depth during drought; Helical piers are screwed in, and installation torque is used to estimate capacity.
What is a bearing stratum?: It is the soil or rock layer strong enough to carry a foundation's load without settling. For repair piers, it is the layer the pier is driven or drilled down to.
Shale weathering and bearing: How deep do foundation piers go in Tulsa?: Oklahoma steel push pier installation records show typical depths of about 8 to 16 feet, with a median of about 12 feet in Tulsa. Depth at any one house depends on its soil and rock.
Shale weathering and bearing: Why does it matter if a pier stops in dry clay?: Clay within the active zone changes volume with moisture. A pier that reaches resistance in stiff, dry clay during a drought may still be in soil that swells or softens when it rewets.
Shale weathering and bearing: What is the difference between soft and hard rock in soil surveys?: USDA soil descriptions call the top of soft, weathered rock that can still be dug a paralithic contact, and the top of hard rock a lithic contact.

How do erosion, creeks and slopes threaten Oklahoma foundations?

Runoff can undermine slab edges, creeks can cut into banks, clay on slopes can creep, and underground flow can carry soil away and leave voids.

Erosion, creeks and slopes: How does water take soil away?: Flood-plain soils show how active these settings are. Port soils, on narrow flood plains in central Oklahoma, flood occasionally or frequently for very brief periods during March to October.
Erosion, creeks and slopes: What are other warning signs?: Besides exposed slab edges and leaning walls or trees, sign pages on this site cover a sudden depression or sinkhole, which can mark underground soil loss, and water ponding near the foundation, which shows where runoff collects.
Erosion, creeks and slopes: How are these problems repaired?: Because steep slopes, bare ground and heavy rain drive erosion, repair options focus on the water and the slope as well as the house. They are described on slope and erosion stabilization and drainage solutions.
Can erosion undermine a house foundation?: Yes. Concentrated runoff or floodwater can wash soil out from under slab edges and footings, leaving them unsupported. Steeper slopes and bare ground increase the chance of erosion.
Are houses near creeks at more risk?: Houses near streams can lose support if the bank erodes, and flood-plain soils can flood. Removing long-term plant cover along streams can lead to significant erosion from stream flow.
Erosion, creeks and slopes: What is slope creep?: Slope creep is the slow, gradual downhill movement of soil. On clay soils, dry spells open deep cracks, and water entering those cracks in intense rain makes the soil swell; on slopes, these cycles can add to the movement.
Erosion, creeks and slopes: Is heavy rain getting more common in Oklahoma?: NOAA reports that 2-inch extreme rainfall events in Oklahoma have increased since 1985 and projects more extreme precipitation, which raises flood risk and soil erosion.

How do freezes and frost affect Oklahoma foundations?

Frost is a secondary issue in most of Oklahoma; freezes mainly affect porches, steps, driveways and plumbing, more so in the northwest and Panhandle.

How does frost move soil?: Frost heave happens when water in the soil freezes and expands, pushing shallow concrete or footings upward; it settles back, often unevenly, when the ground thaws.
Freeze-thaw and frost depth: What is Oklahoma's winter climate like?: Winters are shorter and less severe than in the northern Plains states; The Oklahoma Climatological Survey describes frozen soil as rare and brief; Temperatures at or below 32°F occur on average about 60 days a year in the southeast.
How does frost compare with clay movement?: Frost heave is seasonal and limited to the depth that actually freezes. Clay shrink-swell responds to moisture and follows wet and dry cycles rather than cold spells, and the depth of seasonal moisture variation is typically 15 feet or more.
Is frost heave a big problem for Oklahoma foundations?: Usually less than in northern states. Oklahoma's winters are shorter and milder than the northern Plains, and frozen soil is described by the state climatologist as rare and brief. Shrink-swell clay is the more common cause of movement.
Freeze-thaw and frost depth: Where does Oklahoma get the most freezing weather?: Snowfall rises from under 2 inches a year in the far southeast to nearly 30 inches in the western Panhandle, so cold-season effects are strongest in the northwest and Panhandle.
How can a hard freeze cause foundation problems?: Mostly through water. Frozen or burst pipes can release water under a slab or into a crawl space, and wet clay can then swell or soft soil can lose support.
Can Mesonet soil moisture data be used during a hard freeze?: Not reliably. The Mesonet notes that soil moisture can't be measured when the ground is frozen, so winter soil moisture maps may have large gaps.

How do Oklahoma drought and wet cycles move foundations?

Oklahoma clay shrinks in drought and swells when wet, so foundations drop at the edges during drought and can be pushed back up when heavy rain returns.

Drought and wet cycles: Why does the weather cycle matter to a foundation?: Many Oklahoma homes sit on expansive clay, a soil made of very fine clay minerals that swell when water enters and shrink when the soil dries out.
What are Oklahoma's recent droughts and wet spells?: The National Weather Service in Tulsa links the 2011 drought to La Niña, a cooling of the equatorial Pacific that shifts the jet stream north and raises the odds of warm, dry weather in the Southern Plains.
Drought and wet cycles: How can you track where the cycle is?: U.S.
Why do foundation cracks show up during an Oklahoma drought?: Expansive clay soils shrink as they dry. When the soil around the edge of a house dries faster than the soil under the middle, the perimeter can drop and cracks open in brick, drywall and slabs.
Can heavy rain after a drought cause foundation problems too?: Yes. Dry clay swells when it takes on water again, so a sudden wet period after a drought can push parts of a foundation upward. Studies of the 2011 drought found it increased the potential heave of clay soils.
How bad was the 2011 drought in Oklahoma?: Summer 2011 was Oklahoma's hottest on record at an average of 86.9°F, and the state's 2011 rainfall was about 11 inches below normal. By early January 2012 nearly 79% of the state was still in moderate drought or worse.
Drought and wet cycles: What was Oklahoma's wettest year on record?: 2015. The statewide average was 53.88 inches, beating the 1957 record, and May 2015 was the wettest month in state history at 14.40 inches.
Where can I check current drought conditions in Oklahoma?: The U.S. Drought Monitor publishes an updated map every Thursday, and the Oklahoma Mesonet posts daily soil moisture readings from stations statewide.

How do Oklahoma storms, floods and ice affect foundations?

Water is the main way severe weather reaches a foundation: floods and heavy rain saturate clay and wash out soil, while wind and tornadoes act on the structure.

How severe is Oklahoma's weather by the numbers?: From 1985 to 2019 Oklahoma averaged 60 tornadoes a year, with peaks in April and May; About three-fourths of the state's tornadoes have occurred in April, May and June; autumn is a secondary severe weather season; Flooding is most frequent in the spring and autumn months that bring the most rain.
How does each weather event affect foundations?: After flooding or leaks, the EPA advises drying water-damaged areas and items within 24–48 hours to prevent mold.
How does weather relate to insurance questions?: Storm-related claims often raise the question of whether damage came from the storm or from long-term soil movement.
Severe weather effects: Can flooding damage a house foundation?: Yes. Floodwater saturates soil, which can make clay swell, soften soil under footings, push on basement walls and wash soil out from under slab edges.
Severe weather effects: Are heavy rains in Oklahoma getting more common?: NOAA reports that the number of 2-inch extreme rainfall events in Oklahoma has increased since 1985, and projects further increases in extreme precipitation, with higher flood risk and more soil erosion.
When is Oklahoma's severe weather season?: Spring is the main season, with about three-fourths of Oklahoma's tornadoes occurring in April, May and June. Autumn is a secondary severe weather season.
Severe weather effects: Why do foundation problems show up after a big rain following drought?: Clay that dried and shrank during drought swells quickly when it gets wet again, so parts of a foundation can rise or cracks can shift soon after the drought breaks.

How do Oklahoma's geologic regions affect foundations?

Pennsylvanian shales and sandstones in the east and Permian red beds in central and western Oklahoma shape soil, clay content and depth to firm material.

What are Oklahoma's geologic provinces?: The Oklahoma Geological Survey's 2024 structural and tectonic map names the state's major provinces:
Oklahoma geologic provinces: What did eastern and western soils form from?: USDA soil descriptions record the rock each soil weathered from, which shows the east-west split clearly:
Why do geologic regions matter for foundations?: USGS karst mapping outlines rock units containing significant carbonate or evaporite minerals (gypsum is an evaporite) as soluble rocks that have developed or could develop karst features, such as sinkholes. See gypsum karst and sinkholes.
What rock is under Tulsa versus Oklahoma City?: Soils around Tulsa commonly formed from Pennsylvanian-age shale and sandstone, while soils around Oklahoma City commonly formed from Permian-age red shale, claystone and sandstone.
What are Oklahoma's main geologic provinces?: The Oklahoma Geological Survey's structural map names the Ozark Uplift, Cherokee Platform, Arkoma Basin, Ouachita Uplift, Arbuckle Uplift, Wichita Uplift, Anadarko Basin, Ardmore and Marietta basins, Hollis-Hardeman Basin and Nemaha Uplift, among others.
Where in Oklahoma is gypsum near the surface?: Gypsum of the Permian Blaine Formation forms shallow bedrock in parts of western and southwestern Oklahoma. Some soils there sit only inches above massive gypsum.
Does rainfall differ across Oklahoma's regions?: Yes. Average annual precipitation ranges from about 17 inches in the far western Panhandle to about 56 inches in the far southeast.

How do you tell foundation heave from settlement?

Heave is ground rising, usually as clay takes on water; settlement is ground dropping. Floor surveys over time, the season and water sources tell them apart.

What are heave and settlement?: Post-Tensioning Institute (PTI) evaluation guidelines define heave as upward movement of an underlying supporting soil layer and settlement as downward movement of that layer. On expansive clay, heave happens when moisture is added and shrinkage happens when moisture is removed.
What drives heave and settlement?: Some notes on the table:
Heave vs settlement: Why is a single survey not enough?: An elevation survey maps high and low areas, but PTI notes that unless a benchmark is used, contours alone do not show whether heave or subsidence occurred. A center that reads high could be a center that rose, or edges that fell.
Heave vs settlement: Which tests help decide?: Plumbing tests. ASCE Texas guidelines list plumbing testing as part of a more detailed investigation and say water supply and drain lines should be tested for leaks if lifting is part of the repair.
Heave vs settlement: Why does the call matter?: Lifting is aimed at raising low areas. If a high area is high because it heaved, raising the surrounding foundation does not address the added water that caused it.
What is the difference between heave and settlement?: Heave is upward movement of the soil supporting a foundation, usually from clay taking on water. Settlement is downward movement, often from clay drying and shrinking or from soft or poorly compacted soil compressing.
Heave vs settlement: Why does it matter which one is happening?: The fixes are different. Settlement is often addressed by supporting or lifting the low areas, while heave is driven by added water, so finding and stopping the water source is central. Lifting a foundation also calls for testing plumbing lines for leaks.
Can a floor survey tell heave from settlement?: A single survey shows high and low areas but, without a fixed benchmark, not which areas moved up or down. Comparing surveys taken at different times shows the actual direction of movement.
Can removing a tree cause heave?: Yes. Engineering guidelines note that removing a large tree can let soil rewet and swell, and may recommend waiting before repair to allow for that heave.

How does yard drainage and grading affect an Oklahoma foundation?

On expansive clay, slopes toward the house, downspouts at the wall and sprinklers wet soil unevenly and drive movement; fixing drainage is a first step.

Why does surface water matter?: Expansive clay swells when water enters it and shrinks when it dries, and uneven moisture under a slab causes differential movement, where one part of the house moves more than another.
What drainage problems are common on Oklahoma lots?: Signs that water is collecting include water ponding near the foundation and, after dry spells, soil pulled away from the foundation.
How does drainage connect to foundation movement?: Edge lift: when the perimeter gets wetter than the center, the edges can rise; see perimeter wetting heave; Edge drop: when the perimeter dries faster, the edges can fall; see perimeter drying settlement; Washouts: concentrated runoff can carry soil from under slab edges; see erosion, creeks and slopes.
Surface drainage and grading: Which way should the ground slope around my house?: Away from the foundation. The EPA advises making sure the ground slopes away from the building so water does not collect around the foundation.
Surface drainage and grading: Where should downspouts drain?: EPA guidance describes redirecting downspouts to a rain barrel or to a lawn or garden where water can soak in, while considering where the water will go so it doesn't cause property damage.
Surface drainage and grading: Can lawn sprinklers affect my foundation?: They can. Engineering sources list irrigation among the causes of uneven soil moisture under foundations on expansive clay, along with poor drainage, leaks and trees.
Why does drainage matter so much on Oklahoma clay?: Expansive clay swells when wet and shrinks when dry. Water that collects along one side of a house wets that side more than the rest, which causes uneven movement.

How far apart are foundation piers in Oklahoma?

Spacing depends on wall load, pier capacity and how far the beam can span. Oklahoma steel push piers are commonly set about 7 feet apart.

Pier spacing and capacity: Where does the load come from?: A house's weight reaches the soil through its perimeter beam or footing. Engineers express this as a line load: pounds per linear foot of wall. It adds up from the roof, the walls, the floors and the concrete itself. Brick veneer adds a large share.
How is pier spacing worked out?: In plain terms, spacing is limited by whichever of these runs out first: - Pier capacity. The load one pier can carry, divided by the line load, gives the longest spacing the pier allows. - Beam span. The concrete beam between two piers has to carry the wall like a bridge.
How is pressure read on a pier log?: A steel push pier is driven by a hydraulic ram that pushes against the weight of the house. The gauge pressure when the pier stops, multiplied by the ram piston's area, equals the force applied to the pier.
Pier spacing and capacity: How does frost depth affect shallow systems?: Oklahoma's engineering board described common "pier and grade beam" systems: grade beams about 8 to 10 inches wide and 14 to 18 inches deep, on piers 8 to 10 inches in diameter, no more than about 36 inches deep and 6 to 8 feet apart.
Pier spacing and capacity: How does expansive clay cause uplift?: The active zone is the depth of soil whose moisture changes with the seasons. In that zone, swelling clay can grip a pier shaft and pull up on it.
What drives the number of piers?: Length of wall that has settled; Weight of the structure (one or two stories, brick or siding); Condition and reinforcing of the existing beam.
How far apart are foundation piers usually placed?: Oklahoma steel push pier records show exterior piers placed about every 7 feet along affected walls. The right spacing for a given house depends on the wall load, the pier capacity and how far the concrete beam can span between supports.
What does the psi number on a pier log mean?: It is the hydraulic pressure in the driving ram when the pier stopped. Multiplying that pressure by the ram's piston area gives the force pushing on the pier, which is why the ram size must be recorded to turn psi into a load.
Why does expansive clay matter for pier design?: Clay in the active zone swells and shrinks with moisture, and building codes require foundations placed in that zone to be designed to resist the resulting volume changes.
Are shallow pier-and-grade-beam systems always adequate?: Not always. Oklahoma's engineering board described common shallow systems that sit above frost depth and showed by calculation that one typical layout could carry only about 5 to 6 feet of brick wall height before other loads were counted.

How far out of level can an Oklahoma foundation be?

There is no single allowed number. Engineers judge overall tilt, deflection and resulting distress against published guidelines.

Foundation tolerances: Why is "level" the wrong yardstick?: Forensic engineers point out that foundations are not built perfectly level, so a floor-level survey always mixes original construction variation with any movement since. Porches, patios and garages are often built with deliberate slopes for drainage.
Foundation tolerances: What are tilt, deflection and distress?: Engineering guidelines separate two kinds of out-of-level: - Tilt: a plane sloping evenly across the whole foundation. - Deflection: how far the surface bows away from a straight line drawn between two points.
Foundation tolerances: What does Oklahoma's residential code cover?: The Oklahoma Uniform Building Code Commission adopts the IRC statewide. The 2024 IRC with Oklahoma amendments took effect September 14, 2026. The prior 2018 edition with Oklahoma amendments had been effective since September 14, 2022.
Foundation tolerances: What does the code say about expansive soil?: Where data suggest expansive, compressible or shifting soils, the building official decides whether a soil test is required. Soil counts as expansive when all four of these are met, though the first three need not be tested if the fourth is run:
Foundation tolerances: Does a repair plan need an engineer's seal?: In Oklahoma, a foundation repair plan prepared by an engineer must be signed, sealed and dated, and the engineer keeps a design file with criteria, calculations and the cause of the damage. See working with engineers.
Foundation tolerances: Is any house floor perfectly level?: No. Forensic engineering literature states that foundations are not constructed perfectly level, so an elevation survey shows original construction variation as well as later movement.
What guidelines do engineers use to evaluate a residential foundation?: Commonly cited documents include the Texas Section of ASCE's Guidelines for the Evaluation and Repair of Residential Foundations and the Post-Tensioning Institute's guide for performance evaluation of slab-on-ground foundations, both of which look at deflection and distress.
Foundation tolerances: Which building code applies to houses in Oklahoma?: The 2024 International Residential Code with Oklahoma amendments became the statewide minimum residential code on September 14, 2026, replacing the 2018 edition adopted in 2022.
Foundation tolerances: How does the building code define expansive soil?: The residential code treats soil as expansive when it has a plasticity index of 15 or more, more than 10% passing a No. 200 sieve, more than 10% of particles finer than 5 micrometers, and an expansion index above 20; if the expansion index test is run, the other three are not required.

How is a foundation elevation survey done?

Floor heights are measured from one reference point and mapped as contours, then tilt and deflection are checked against limits such as L/360 and 1 percent.

What does an elevation survey show?: A floor elevation survey records the shape of a foundation at one instant.
Foundation elevation surveys: How are readings taken?: The Foundation Performance Association (FPA) guideline calls for a level-measuring device accurate to plus or minus 1/8 inch or better, and says a spirit level should not be used to measure slab slope.
Foundation elevation surveys: How are the results read?: Tilt is the whole foundation sloping one way, like a tabletop with short legs at one end; Deflection is bending, where the middle is higher or lower than a straight line between two points, giving a dome or dish shape.
Foundation elevation surveys: Why repeat a survey?: Time-change elevations are calculated by subtracting the older reading from the newer one at each point, using equivalent plans and the same locations. PTI notes time-change contours are typically drawn at 0.5-inch increments.
What is a foundation elevation survey?: It is a set of relative floor height readings taken across a house from one reference point, then drawn as a contour map. It shows the shape of the foundation, such as which areas are high or low.
Foundation elevation surveys: Is a new slab built perfectly level?: No. Guidelines citing the concrete tolerance standard ACI 117 treat about 1.5 inches of total out-of-levelness (plus or minus 3/4 inch) as acceptable construction, and one Texas committee found most residential slabs within about 1 inch.
Foundation elevation surveys: What deflection and tilt numbers do engineers use?: Common guidelines use a deflection ratio of L/360 as a screening limit and a tilt of 1 percent or less across the whole length, width or diagonal. These are compared with visible distress, not used alone.
Foundation elevation surveys: Can one survey tell if my house heaved or settled?: Usually not by itself. Without a fixed benchmark, contours show shape but not whether an area rose or fell; comparing two surveys over time is the direct way to measure movement.
Foundation elevation surveys: Can I use a carpenter's level or marbles?: Foundation evaluation guidelines say a spirit level should not be used to measure slab slope and call for an instrument accurate to about 1/8 inch or better.

How is a settled foundation lifted, and what happens after?

Piers raise settled areas toward original height, aiming for the best practical lift, not flat, followed by plumbing checks, a new survey and pier records.

What does "lifting" mean?: Once piers are installed under a settled section, hydraulic jacks set on the pier brackets push the foundation up. A pier is a steel or concrete column driven or drilled down to firmer soil or rock so the house no longer rests only on the shallow clay.
Foundation lifting and restoration: Why is "level" not the goal?: Forensic engineers note that foundations are not constructed perfectly level, so a survey reflects as-built variation plus movement since construction.
Foundation lifting and restoration: What checks follow the lift?: Expansive-soil guidance from forensic engineers recommends three steps after any lifting or lowering: 1. Plumbing tests to find leaks that the movement may have caused, especially in drain lines under the slab. 2.
Foundation lifting and restoration: Which records matter later?: Each pier's depth, final pressure and final elevation are recorded on Oklahoma installation logs. These records serve several later uses:
What restoration work follows?: After the structure stops moving, cosmetic work can follow: brick mortar repair (tuckpointing), drywall patching, and door and trim adjustment. Doing this work before the house has settled into its new position risks re-cracking.
Will lifting make my house perfectly level?: No. Foundations are not built perfectly level to begin with, so an elevation survey after a lift shows original construction variation as well as any movement. The practical goal is to recover as much settlement as the structure allows without causing new damage.
Should the plumbing be tested after a foundation is lifted?: Forensic engineering guidance recommends plumbing tests after any lifting or lowering to check for leaks, with any leaks repaired, followed by a new baseline elevation survey.
Foundation lifting and restoration: How hard is each steel pier pushed during installation?: Oklahoma installation records show steel push piers driven to at least 6,000 psi of hydraulic pressure, with a median near 9,000 psi on a large Tulsa job, and each pier's depth and pressure logged.
Do I have to disclose a foundation repair when I sell?: Yes, if you know about it. The Oklahoma disclosure form asks sellers directly whether they are aware of any previous foundation repairs and whether any warranties, including foundation warranties, cover the property.
Foundation lifting and restoration: Who can sign an engineering completion letter in Oklahoma?: Only a licensed professional engineer. Oklahoma's engineering board says a repair company may send its own completion letter but may not call it an engineering completion letter.

Is it earthquake damage or soil movement in my Oklahoma home?

Earthquake damage appears at a set moment tied to a recorded event; expansive clay damage builds over months or years and changes with the seasons.

Earthquake vs soil damage: Why does this question come up in Oklahoma?: Oklahoma has had far more earthquakes since 2009 than before, and much of the state has expansive clay soil that moves with moisture. Both can crack drywall, brick and slabs, so homeowners and insurers often need to know which one did it.
Earthquake vs soil damage: What are the typical documentation steps?: Pull the earthquake record. The OGS catalog lists date, location and magnitude for Oklahoma events; Did You Feel It? maps reported shaking; Establish when damage was first seen.
Can a small earthquake crack my foundation?: Damage generally starts around intensity VI on the Modified Mercalli scale, described as minor damage such as some falling plaster and a few cracks.
Earthquake vs soil damage: How do I know how hard the ground shook at my house?: The USGS Did You Feel It? system maps shaking reported by people for each earthquake, and the Oklahoma Geological Survey publishes catalogs with the date, location and magnitude of Oklahoma events.
What does foundation damage from clay soil look like?: Soil-related damage usually builds over time: cracks in walls and foundations, then sticking doors and sloping floors. It follows the shape the slab has been bent into, such as edges dropping or the center rising.
Do earthquake hazard estimates account for damage from many small quakes?: Not fully. The Oklahoma Geological Survey noted that the 2016 USGS hazard model for Oklahoma did not address cumulative damage from multiple small-to-moderate earthquakes over time.

What affects the cost of foundation repair in Oklahoma?

Scope drives cost: the cause of movement, foundation type, number and depth of supports, access, drainage and plumbing work, engineering, permits and follow-up.

What sets the scope of a foundation repair?: Repair options for foundations on expansive clay fall into two groups: - Non-structural: watering programs, vegetation changes, root barriers, gutters and downspouts, grading, subsurface drains and moisture barriers. - Structural: underpinning (adding supports under the foundation), grouting, mudjacking, crack injection and, for post-tensioned slabs, re-stressing tendons.
Foundation repair cost factors: Why does the cause of movement matter?: Settlement or heave. Settlement is the foundation sinking; heave is clay swelling and pushing it up. Piers stop settlement where they are placed, but those areas can still heave, and a slab supported only in part can both heave and settle.
How do foundation type and support points change the work?: Slab on grade: structural options include underpinning, grouting, mudjacking and crack injection; Pier and beam: repair can involve shimming the floor, framing repairs, added supports and crawl space moisture control; Interior support points: in Oklahoma installation records, piers pushed at the interior slab stopped at about 8 to 11 feet and 4,000 to 5,000 psi, while piers at the perimeter footing reached about 13 to 17 feet and 7,000 to 8,000 psi.
Foundation repair cost factors: Why does depth to bearing soil or rock matter?: A bearing stratum is a layer of soil or rock firm enough to carry the load.
Foundation repair cost factors: What other work can be part of the job?: Engineering. Under Oklahoma's engineering board guidelines, a professional engineer visits the site or directs a technician, then issues a signed, sealed and dated repair plan or a sealed statement that no pier repair is needed; the repair company carries out that plan.
Foundation repair cost factors: How do warranty terms and insurance fit in?: Warranty. Foundation performance after repair is judged against the standard written into the contract or warranty.
Why do repair proposals for the same house differ so much?: Proposals can assume different causes of movement, different numbers and depths of support points, and different extras such as drainage work, plumbing tests, engineering, permits, restoration and monitoring. Listing what each proposal includes shows where they differ.
Foundation repair cost factors: Why is pier depth not known before the work starts?: Steel push piers are pressed until they meet resistance and helical piers are turned to a set torque, so the final depth is found during installation. In one set of Tulsa installation records, 396 piers stopped at a median of 12 feet, with a range of 2 to 40 feet on the same site.
Does homeowners insurance pay for foundation repair?: Usually not when soil movement is the cause. The standard homeowners form excludes earth movement regardless of its cause, and an insurance coverage analysis applied that exclusion to a foundation cracked during drought. The policy's own wording controls.
Foundation repair cost factors: Does an engineer have to be involved?: Oklahoma's engineering board guidelines say that when a professional engineer is involved, the repair plan must be signed, sealed and dated and the repair company carries out that plan. Cities such as Tulsa can also require construction plans for structural repair permits.
Why might repairs wait while the house is monitored?: Monitoring guidelines call for at least three elevation surveys over at least one year to tell seasonal movement from ongoing movement. Repairs to cracks and finishes made after movement has stopped are less likely to reappear.

What are loess and collapsible soils in western Oklahoma?

Loess is wind-deposited silt, found mainly on Oklahoma Panhandle tablelands. Loose, dry wind-laid soils can collapse when wetted, the reverse of swelling clay.

What are loess and eolian soils?: Loess is silt that wind picked up and dropped in sheets across the landscape. Eolian simply means wind-deposited, and covers sandy deposits as well as silt.
Loess and collapsible soils: How does collapse differ from swell?: A collapsible soil is a loose, low-density soil that holds its shape while dry but loses volume when water soaks in under the weight of a building. The result is settlement, often sudden and concentrated where water entered. The mechanism is described on the hydrocollapse page.
Loess and collapsible soils: Which water sources matter?: Because wetting triggers collapse, the source of water matters: plumbing leaks, roof runoff, irrigation and poor grading. A simple supply-leak check is to read the water meter, use no water for two hours, and read it again; any change probably means a leak.
How are collapsible soils repaired?: Repair options on collapsible ground are compared on the method selection matrix. They include piers taken through the loose layer to firmer support, such as steel push piers or helical piers, void and compaction grouting in some cases, and drainage control.
What is loess?: Loess is silt that was carried and deposited by wind. In Oklahoma, the Richfield soil of the Panhandle tablelands formed in calcareous loess 3 to more than 10 feet thick.
Where are loess soils found in Oklahoma?: Mainly in the Oklahoma Panhandle. The Richfield series, formed in loess, is mapped there, and wind-deposited sandy soils such as the Dalhart series have their type location in Cimarron County.
What is a collapsible soil?: It is a loose, dry soil that holds its shape while dry but can lose volume when it is wetted under a load, causing sudden settlement. It is the opposite reaction to water from expansive clay, which swells.
Loess and collapsible soils: Is the Ulysses soil mapped in Oklahoma?: No longer. The official USDA description for the Ulysses series, a loess soil, notes that Oklahoma was removed from its range in 2016.

What bedrock is under Oklahoma City homes?

Mainly Permian red-bed Hennessey shale and Garber sandstone; the clay soils formed from these rocks, not the rock itself, cause most shrink-swell movement.

Bedrock under OKC: What are the main rock units?: The Hennessey is about 90 meters (roughly 300 feet) thick in the USGS study area, and its near-surface layers in western Oklahoma County dip gently west-southwest toward the Anadarko Basin.
Bedrock under OKC: How deep is rock?: On Hennessey shale (I-35/I-240): soil of lean clay, silt and sand extended about 2 to 16 feet, and bedrock was reached at 16, 5.5, 2, 2 and 2 feet in five borings. The report notes that shale weathering is erratic and can change over short distances.
Bedrock under OKC: Where do groundwater and perched water occur?: At the Hennessey site, most borings were dry, but lab tests showed high saturation in some soil as shallow as 3 feet, and the report warns of perched water in the soil or at the soil-rock contact that changes with the seasons.
Bedrock under OKC: How does the rock differ from the soil on top?: The Hennessey shale in a USGS core taken below the soil was mostly illite and kaolinite, clay minerals with low shrink-swell potential. The soils that form on Permian shales tell a different story.
Bedrock under OKC: What does it mean for foundations?: Shallow Hennessey rock usually means shorter piers, but rock depth can change sharply between neighboring borings; On thick soil over Garber sandstone, competent rock at the boring site (20.5 to 95 feet) lay well below the 8 to 16 foot depths typical of Oklahoma push pier installation records, so piers there may stop in dense soil rather than on rock; At the I-35/I-240 site, alluvium lies over the Hennessey shale.
What rock is under Oklahoma City?: Mostly Permian red beds. The Hennessey Group, a red-brown shale with siltstone and some sandstone, underlies large parts of the metro, and the Garber Sandstone, a red cross-bedded sandstone with red shales, underlies other areas including north Edmond borings.
How deep is bedrock in Oklahoma City?: It varies widely. Highway borings on Hennessey shale near I-35 and I-240 found rock between about 2 and 16 feet, while borings on Garber sandstone near I-35 and Waterloo Road found overburden 20 to more than 90 feet thick.
Bedrock under OKC: Is the Hennessey shale itself expansive?: A USGS study found the Hennessey shale cored below the soil at a northwest Oklahoma City site was mostly illite and kaolinite with low shrink-swell potential; the swelling problems are mainly in the clay soils that form from these rocks.
Bedrock under OKC: Why does depth to rock matter for my house?: Driven and drilled piers get much of their support from firm soil or rock, so shallow rock usually means shorter piers, while thick soil over deep rock means piers may stop on friction in dense soil instead.

What bedrock is under Tulsa, Oklahoma homes and how deep is it?

Mostly Pennsylvanian shale with sandstone and limestone; upland borings usually hit rock within 4 to 20 feet, river banks have 18 to 35 feet of sediment.

What rock layers are under Tulsa?: Engineering reports across the metro describe the same basic pattern: clay soil over shale, with sandstone and limestone layers mixed in.
Tulsa bedrock depth: How deep is rock in public borings?: At I-44/US-75, one boring hit a well-cemented sandstone layer near the surface with a significant thickness of sandy lean clay beneath it, and the report said it should not be considered competent rock. A hard layer near the surface is not always the bottom.
What is under Tulsa's river corridors?: Alluvium is sediment laid down by rivers. Along the Arkansas River it is mostly poorly graded sand to silty sand with infrequent clay seams and low gravel content, very loose to loose, with clay layers that are very soft to soft.
Tulsa bedrock depth: What clay sits on top of the rock?: The soil over Tulsa shale can be highly plastic. Lab tests on the 91st Street walls found fat clay with plasticity indices up to about 39, and east Tulsa samples ranged from 23 to 34.
Tulsa bedrock depth: How does water behave on the shale?: Five of nine east Tulsa borings recorded water at some point, at depths from 3.5 to 18.5 feet, with end-of-drilling readings of 7 to 9.5 feet; the others were dry. The 91st Street report found water at 13.5 to 15 feet along one wall and dry borings along the other.
How deep do Tulsa piers go?: On one large Tulsa site, 396 logged steel push piers refused at a median of 12 feet, with the middle half between 9 and 14 feet and a range of 2 to 40 feet, at a median pressure of about 9,000 psi.
What kind of rock is under Tulsa?: Mostly gray shale of Pennsylvanian age, with sandstone and thin limestone layers. Engineering reports in the metro name units such as the Nowata, Holdenville, Nellie Bly, Wewoka and Senora.
How deep is rock in Tulsa?: Public borings on upland shale commonly reached weathered or competent rock between about 4 and 20 feet, while borings on Arkansas River banks found 18 to 35 feet of river sand and clay over the shale.
How deep do foundation piers go in Tulsa?: On one large Tulsa site with nearly 400 logged steel push piers, the median refusal depth was 12 feet, with half of piers between 9 and 14 feet and a full range of 2 to 40 feet.
Why do Tulsa crawl spaces and yards stay wet after rain?: Water often sits on top of tight shale or clay layers as perched water; Tulsa borings that found water commonly found it at shallow depths above or near the rock.

What causes common foundation symptoms in Oklahoma homes?

Most foundation symptoms have more than one possible cause; in Oklahoma, clay soil that shrinks and swells with moisture is widespread.

How do you use this table?: Start with the symptom you see, then read the matching sign and cause pages; for example, a stair-step crack wider at the top usually leads to perimeter drying settlement, and an interior floor hump often leads to center heave or leak-induced heave.
Why do symptom patterns matter?: The location of damage relative to a water source can separate causes. In one documented claim, settlement was concentrated along the footings nearest a plumbing leak, with little or none about 5 feet away.
Symptom lookup table: Does a crack in my wall mean my foundation is failing?: Not by itself. A single crack does not necessarily mean serious structural damage. Engineers evaluate distress together with tilt and deflection measured on an elevation survey.
Symptom lookup table: What are the common warning signs of foundation movement in Oklahoma?: Commonly reported signs include new or widening cracks in brick or drywall, stair-step cracks in brick, sloped floors, doors or windows that suddenly stick, trim pulling away, and a gap between the soil and the house.
Symptom lookup table: Can a home inspector tell me what is causing the movement?: No. Oklahoma's home inspector standards require inspectors to describe indicators of foundation or structural movement, but they are not required to determine the cause or the repair method.
Can one symptom have more than one cause?: Yes. A sloping floor, for example, can come from perimeter drying, fill settlement, soft soils or framing problems, which is why the pattern of several symptoms and a floor-level survey are used together.

What do foundation crack patterns in a house mean?

Stair-step brick cracks, cracks at door and window corners, sticking doors and sloping floors are movement clues, checked against floor elevation surveys.

How do engineers treat distress signs?: The Texas Section of the American Society of Civil Engineers (ASCE) lists 12 visible indications of foundation movement, including cracking or separating of exterior walls, rotating or buckling brick veneer, cracking of concrete foundation elements, cracking of drywall, walls separating from ceilings or floors, racking of door and window frames, and cracking or buckling of floor coverings.
What patterns show up in each part of a house?: Stair-step cracks that follow mortar joints in brick are one of the exterior signs listed in the ASCE homeowner guide.
Distress pattern library: What is truss uplift, a common look-alike?: Canada Mortgage and Housing Corporation explains truss uplift: roof trusses bow upward when the warmer, drier bottom chord (buried in attic insulation) shrinks more than the top chord.
Distress pattern library: How is crack width graded?: The Foundation Performance Association guideline allows crack widths to be recorded but does not set a severity scale. The UK Building Research Establishment (BRE) publishes damage categories for houses based on crack width:
Distress pattern library: Do cracks always mean my foundation is failing?: No. Engineering guidelines note that most cracks do not compromise structural integrity and that seeing some distress does not by itself mean a foundation is performing poorly. Patterns, crack widths, change over time and floor elevations are evaluated together.
Distress pattern library: How wide does a crack have to be to matter?: A widely used UK building research scale treats cracks up to about 5 mm (roughly 3/16 inch) as mainly cosmetic, 5 to 25 mm as affecting serviceability, and over 25 mm as possible structural damage. The number of cracks and whether they are growing also count.
Distress pattern library: Why is there a gap between my ceiling and an interior wall in winter?: A common cause is truss uplift, where roof trusses bow upward as the attic-side lumber changes moisture content. The gap typically opens in winter and closes in summer and is not caused by the foundation.
Distress pattern library: What signs do home inspectors look for?: Inspection standards list cracked drywall or brick, out-of-square door frames and unlevel floors as possible indications of foundation movement that should be reported.

What do soil test numbers for expansive clay mean?

The plasticity index from Atterberg limits is a common quick indicator of shrink-swell, while swell tests measure movement and pressure directly.

Soil test numbers: How do you read the plasticity index?: A commonly cited structural engineering rule of thumb:
Soil test numbers: What do Oklahoma lab results show?: An Oklahoma State University study of benchmark soils measured liquid limits, plasticity and swell:
Soil test numbers: Why does the moisture state matter?: The same clay can show different behavior depending on how dry it is when tested. A study of clay sites during the 2011 drought found the drought increased the soils' potential vertical rise, meaning more possible heave once they rewet.
Soil test numbers: How many borings and samples are needed?: How a site is sampled shapes what the lab can report. As one example of a written requirement, a Virginia county policy for expansive soil areas calls for:
What soil test shows whether clay is expansive?: The Atterberg limits test, which gives the liquid limit and plasticity index, is a common quick indicator. Swell tests measure the actual swelling and the pressure it can produce, but they are run less often.
Soil test numbers: What plasticity index means highly expansive clay?: One engineering rule of thumb treats clays with a plasticity index under about 20 as only marginally expansive and clays above about 40 as highly expansive.
How deep should soil borings go for a house?: Requirements vary by jurisdiction. As one example, a county expansive-soil policy calls for at least two borings in the building footprint, at least 5 feet deep or to refusal on non-expansive material.
Are there lab results for Oklahoma soils?: Yes. A 1978 Oklahoma State University bulletin tested benchmark soils and found Kirkland subsoil had a liquid limit above 50% and was highly expansive, while Bethany and Norge were rated moderate and sandy soils slight for low buildings.

What does a full foundation inspection include?

It covers desk research, a homeowner interview, exterior and interior walks, a floor elevation survey, a crawl space or basement check and a report.

Foundation inspection steps: What are the levels of investigation?: The Texas Section of the American Society of Civil Engineers (ASCE) defines three levels of residential foundation investigation:
Foundation inspection steps: 1. What desk research happens before the visit?: Background on the lot can be gathered before anyone arrives:
Foundation inspection steps: 2. What is asked in the homeowner interview?: ASCE Texas guidelines call for interviewing the occupant, owner and client, where possible, about the property's history and the structure's performance, and reviewing any documents such as construction drawings or geotechnical reports.
Foundation inspection steps: 3. What is checked on the exterior walk?: The exterior walk records cracks in brick, gaps at windows and doors, and separation of flatwork from the house. The ASCE homeowner guide recommends checking that the ground within 5 feet of the foundation drains water away.
Foundation inspection steps: 4. What is checked on the interior walk?: FPA's guideline calls for recording distress on every interior level and the exterior, noting whether it is on a wall, ceiling or floor, its position relative to doors and windows, and any sign of earlier repair; crack widths may also be recorded.
Foundation inspection steps: 5. How is the elevation survey done?: The floor elevation survey is the Level B step. FPA calls for an instrument accurate to 1/8 inch or better, a repeatable reference point and readings about every 30 to 100 square feet, corrected for floor coverings. Details are on elevation surveys.
Foundation inspection steps: 6. What is checked in the crawl space or basement?: Home inspection standards require describing the foundation type and the crawl space access, and reporting active water penetration, wood in contact with soil and signs of possible foundation movement.
Foundation inspection steps: 7. How are the findings analyzed?: Distress locations are compared with the elevation contour map, the likely mechanism is identified (see heave vs settlement), and moisture sources are listed. Level C adds tests the engineer considers appropriate, such as soil sampling and plumbing testing.
Foundation inspection steps: 8. What goes in the written report?: ASCE Texas guidelines list possible report contents such as the authorization and scope, property description, information sources, collected data, assumptions, analysis, conclusions, recommendations and limiting conditions.
What happens during a foundation inspection?: A typical assessment includes background research on the site, questions about the home's history, a walk around the outside and inside to record distress, a floor elevation survey, a crawl space or basement check if present, and a written report.
Is a home inspection the same as a foundation evaluation?: No. Home inspection standards require inspectors to report signs of possible foundation movement but say they are not required to provide engineering services or judge the adequacy of structural systems.
Foundation inspection steps: What questions will I be asked about my house?: Engineering guidelines call for asking the owner or occupant about the property's history and performance, such as when problems appeared, past repairs, leaks, water bills, watering and tree changes.
Should plumbing be tested during a foundation assessment?: Engineering guidelines list plumbing testing as part of a more detailed investigation and call for testing water and drain lines when lifting is part of the repair.

What foundation does my Oklahoma house have, by year built?

Older Oklahoma homes more often have crawl spaces or basements, while postwar and later homes are mostly on slabs or pier-and-beam.

Foundation type by era: Why does the construction era matter?: It suggests the foundation type before anyone crawls under or measures the floor; It suggests the pipe materials under a slab, which matters when a leak is suspected; It tells which code rules were in force, such as footing reinforcement.
Foundation type by era: What was built in each era?: Newer suburban homes have fewer age-related defects but builder-grade components, and some homes built within the past five years have already developed foundation issues.
Foundation type by era: Why are basements rare in Oklahoma?: Oklahoma has few basements. The director of the Oklahoma Geological Survey has tied this to a high water table and red clay that expands and contracts with soil moisture, which cracks basement walls and lets water in. See basements.
Foundation type by era: What pipes run under the slab?: Mixed ABS and PVC drain piping in older installations can indicate amateur work and leak-prone joints. See plumbing leaks under slab.
Foundation type by era: What are post-tensioned slabs?: A post-tensioned (PT) slab is reinforced with steel cables tightened after the concrete cures. No Oklahoma source located for this page dates when PT slabs came into local use.
Foundation type by era: Why are there so few basements in Oklahoma?: The director of the Oklahoma Geological Survey has pointed to a high water table and red clay that expands and contracts with moisture, which cracks basement walls and lets water in.
What foundations do older Tulsa homes have?: Older central-city Tulsa homes from the oil-boom decades often have aging basements or crawl spaces, while postwar and mid-century homes are on slab and pier-and-beam foundations that move visibly with the expansive clay.
Foundation type by era: When did Oklahoma start requiring more rebar in footings?: Oklahoma's amendments requiring two #4 reinforcing bars in all footings were in the state's 2018-edition residential code rule effective September 14, 2022, and carried into the 2024 edition effective September 14, 2026.
Foundation type by era: What drain pipe is under an older slab?: Cast iron has been used for building drains for more than 100 years, usually as the 4- to 6-inch main drain; some black ABS plastic drain pipe made in the mid-1980s was defective and cracked.

What is perched water and how does it affect Oklahoma homes?

Perched water is rain backed up above a dense clay layer; in eastern Oklahoma it can wet crawl spaces, seep into basements and saturate footing clay.

How is perched water different from the true water table?: Perched water table: a temporary saturated zone sitting on a layer that water passes through slowly, such as dense clay or shale.
Which Oklahoma soils have seasonal shallow water?: Dennis, Okemah, Parsons and Summit are common in the Tulsa area; see soil series - Tulsa metro.
How does shallow water affect houses?: Crawl spaces: standing water, damp framing and condensation (water, condensation or mold in crawl); Basements: seepage at the joint where the wall meets the floor (water at cove joint), and saturated soil pressing on walls; Foundation movement: groundwater is one of the moisture sources engineers list as causing differential movement on expansive clay.
What approaches address shallow water?: Engineering guidance lists dealing with the sources of moisture, including groundwater and drainage, as a first step.
What is a perched water table?: It is a temporary layer of saturated soil that forms when water soaking down from the surface reaches a dense clay layer or rock and can't drain through, so it builds up above it. It sits above the true water table and usually comes and goes with the seasons.
When is perched water most common in eastern Oklahoma?: USDA descriptions of common Tulsa-area soils such as Parsons, Okemah and Dennis place the perched water table from December through April in normal years; for Summit it runs from November through May.
How close to the surface can perched water be?: In Parsons soils the top of the perched water can be just 6 to 18 inches below the surface in winter and spring. In Okemah it is 2 to 3 feet down.
Do houses near rivers have a different water problem?: They can. Flood-plain soils such as Osage have a seasonal high water table 6 to 18 inches deep from November through May, and some flood-plain soils such as Port flood occasionally to frequently.

What is shrink-swell clay and the active zone under a foundation?

Expansive clay swells when wet and shrinks when dry; the active zone is the layer, often several to over 10 feet thick, whose moisture changes enough to move.

Shrink-swell and active zone: What are the key terms?: Shrink-swell: the change in volume of clay soil as its moisture changes. Expansive soils swell when water enters and shrink when they dry; Active zone: the depth of soil whose moisture changes with seasons and other influences, and therefore moves.
Why do some clays swell more?: Clay particles are extremely small, under 2 microns. Smectite clays, including montmorillonite, take water into the spaces between their mineral layers, and that is the main way they swell.
How deep does the active zone go?: There is no single number. Engineers note that active depth is hard to calculate and that local or regional experience is the most effective way to establish it.
Shrink-swell and active zone: What movement patterns does clay cause?: Uneven moisture twists a slab into a center-lift or edge-lift shape. Center lift is linked to long-term moisture gain under older foundations, while edge lift and edge drop follow seasonal or short-term moisture changes. Telling them apart is covered in heave vs settlement.
Shrink-swell and active zone: Why don't piers alone address the cause?: Piers transfer a foundation's weight to deeper soil or rock, which stops a perimeter from going down. Engineering sources note that the first step is dealing with what causes the moisture difference, such as drainage, leaking pipes, trees or irrigation.
What is the active zone in soil?: The active zone is the depth of soil whose moisture, and therefore volume, changes with seasons, droughts, watering and other influences. Below it, moisture stays relatively steady and the soil moves little.
How deep is the active zone?: It varies widely. Studies of Texas clay sites measured roughly 8 to 12 feet, a Houston case found about 28 feet where trees were drying the soil, and Texas-wide estimates range from about 5 feet to more than 30 feet.
Shrink-swell and active zone: What is the difference between center lift and edge lift?: Center lift happens when soil under the middle of a slab is wetter and higher than soil at the edges, often from long-term moisture build-up. Edge lift happens when the soil at the perimeter gets wetter and swells while the center stays drier.
Does drought make the active zone deeper?: It can. A study of clay sites during the 2011 drought found the zone of seasonal moisture change deepened by about 2 feet.
Why do some clays swell more than others?: Swelling depends mainly on the clay minerals. Smectite clays such as montmorillonite absorb water between their layers and swell the most.

What soil types are in the Oklahoma City metro?

Mostly soils from Permian red shale, claystone and sandstone. Clay-rich Renfrow and Kirkland shrink and swell strongly; sandy Dougherty and Lucien move less.

How is a soil series description read?: A soil series is a named soil type that the USDA describes in an Official Series Description (OSD): its layers, clay content, drainage and parent material (the rock or sediment it formed from). OSDs don't give a single "shrink-swell rating," but several details point to it:
What are the major OKC metro soil series?: An Oklahoma State University study of benchmark soils found Kirkland's subsoil liquid limit exceeded 50% with high plasticity indices and described it as highly expansive, with a severe rating for low buildings.
OKC metro soil series: What does this mean for foundations?: Clay-rich series are the ones most associated with perimeter settlement in drought and heave when they rewet; Where soft rock is shallow, as in Lucien and Vernon, the depth of soil that can change volume is limited by the rock below; The underlying rock units are described on the Hennessey Shale and Garber Sandstone pages.
What kind of soil is in Oklahoma City?: Much of the OKC metro has soils formed from Permian red shale and sandstone. Clay-rich series such as Renfrow and Kirkland sit beside sandier series such as Zaneis, Lucien and Dougherty.
Which OKC soils have the most shrink-swell?: Renfrow and Kirkland are clay-rich and show signs of strong shrink-swell, such as slickensides and seasonal cracking. A 1978 Oklahoma State University study found Kirkland highly expansive, with Bethany in the moderate range.
Which OKC-area soils are on flood plains?: Port, Pulaski and Dale formed in loamy stream sediment on flood plains. The official descriptions for Port and Pulaski list occasional or frequent flooding for very brief periods from March to October.
How deep is rock under Oklahoma City soils?: It varies by series. Lucien reaches rippable sandstone in 10 to 20 inches, Vernon has dense claystone at 20 to 40 inches, and Renfrow, Kirkland and Bethany are more than 60 inches deep.
How do I find which soil is under my house?: The USDA soil survey maps soil series by location, but city lots are often graded or filled, so on-site samples or borings are the only way to confirm what is actually under a foundation.

What soil types are in the Tulsa metro and how do they behave?

Tulsa soils formed mostly from shale and sandstone. Shale soils are clayey and can shrink and swell; sandstone soils on hills are loamy and shallow to rock.

How are the official soil descriptions read?: Each soil series has a USDA Official Series Description (OSD) listing its layers, clay content, drainage and parent material (what it weathered from). Terms used below:
How do clay soils formed from shale behave?: Dennis has its type location just north of Claremore in Rogers County. Okemah's subsoil is very firm when moist and has a few slickensides. Parsons has an abrupt change at about 12 inches, where a loamy surface layer sits on a clayey subsoil.
How do sandstone soils on the hills behave?: Bates, Collinsville and Coweta formed from Pennsylvanian sandstone. Coweta, with a type location in Wagoner County, has only 10 to 20 inches of soil over soft sandstone.
Which soils are on Tulsa-area flood plains?: Wynona, Verdigris and Osage formed in alluvium (sediment laid down by streams) on flood plains.
Tulsa metro soil types: How does perched water affect foundations?: Dennis, Okemah, Parsons, Summit, Taloka, Choteau, Wynona and Apperson all list a seasonal perched water table in late fall through spring. That timing lines up with wet crawl spaces and water at basement cove joints described on the groundwater and perched water page.
What kind of soil is in Tulsa?: Most upland soils around Tulsa formed from Pennsylvanian-age shale and sandstone. Shale-derived soils such as Dennis, Okemah, Parsons and Summit are clayey, while sandstone-derived soils such as Bates and Collinsville are loamy and shallow to rock.
Why do Tulsa yards and crawl spaces stay wet in spring?: Several common Tulsa-area soils have a perched water table, a temporary layer of saturated soil sitting on denser clay, from late fall or winter into spring. Parsons, for example, can have perched water 6 to 18 inches down from December through April.
Which Tulsa soils shrink and swell the most?: Summit and Osage are smectitic clays, a clay type prone to swelling. Summit's description notes deep, wide cracks that usually form in summer, and Osage has intersecting slickensides from repeated swelling and shrinking.
Which Tulsa-area soils flood?: Flood-plain soils such as Wynona, Verdigris and Osage formed in stream sediment. Wynona's official description lists occasional very brief flooding from January through July and perched water about 2 feet down from November through April.
Is bedrock shallow in Tulsa?: On sandstone hills it often is. Collinsville reaches hard sandstone within about 4 to 20 inches and Bates within 20 to 40 inches, while shale-derived soils such as Dennis and Summit are more than 60 inches deep.

When do I need an engineer for foundation problems in Oklahoma?

A licensed engineer gives an independent, sealed opinion on the cause and needed repair. Lenders, insurers and buyers may ask for an engineer's report.

When is an engineer commonly involved?: Home sales. Oklahoma's standard sale contract lets buyers hire registered professional engineers and lists a structural inspection as a separate investigation; Mortgage conditions.
What is the difference between structural and geotechnical engineers?: A geotechnical engineer investigates site soils and recommends site preparation and foundation design; a written geotechnical report typically includes soil logs, water table, foundation recommendations, expansive-soil mitigation and expected movements.
How does Oklahoma's board expect repair engineering to work?: The engineering board's compliance guidelines for foundation repair companies set out these steps: 1. A PE (directly or through a repair company) takes responsibility for the project. 2.
What helps an engineer evaluate a house?: An elevation survey with the raw readings; A crack map with dated photos; The soil series from the NRCS soil survey (see soil series in the Tulsa metro).
Who licenses engineers in Oklahoma?: The Oklahoma State Board of Licensure for Professional Engineers and Land Surveyors. The board also authorizes a separate Structural Engineer (S.E.) designation for licensed professional engineers who meet extra exam requirements.
Does a foundation repair plan have to be stamped by an engineer?: When an engineer prepares the plan, Oklahoma's engineering board guidelines say the plan must be signed, sealed and dated, and that the engineer, not the repair company, controls the plan.
What is the difference between a structural and a geotechnical engineer?: A geotechnical engineer investigates the soil and rock and recommends site preparation and foundation design values; a structural engineer designs and evaluates the building's load-carrying parts, such as beams and pier layouts.
When to hire an engineer: Can my home inspector tell me if the foundation needs repair?: Oklahoma home inspectors must describe signs of movement, but they are not required to determine causes, choose repair methods or perform engineering, so reports often recommend further evaluation by a qualified professional.
Will a lender require an engineer's report?: It can. Fannie Mae's rules say that when an appraisal shows abnormal settlement, the lender must show it was corrected or provide a professionally prepared report that it poses no threat of structural damage.

When do Oklahoma foundations move during the year?

Clay swells in wet springs, shrinks in hot, dry midsummer and partly rewets with fall rains, so cracks often open in late summer and narrow in spring.

Why does the calendar matter?: Expansive clay swells when water enters and shrinks when it dries, and uneven moisture under a house causes differential movement. Because Oklahoma's rainfall and evaporation follow a seasonal rhythm, so does much foundation movement.
What is the general seasonal pattern?: Most of Oklahoma's precipitation falls in spring and summer, and the state ranges from under 20 inches a year in the west to more than 50 in the southeast.
Seasonal movement calendar: How much does it vary year to year?: The seasonal pattern is a tendency, not a rule:
Seasonal movement calendar: How can soil moisture be tracked through the year?: The Oklahoma Mesonet reports daily soil moisture as a fractional water index from 0 (very dry) to 1 (very wet). A few points from the sources:
Seasonal movement calendar: When are foundation cracks worst in Oklahoma?: Cracks from shrinking clay tend to open in hot, dry stretches, which in Oklahoma usually means July and August, when rainfall relaxes and evaporation is high. They often narrow again when spring or fall rains rewet the soil.
Seasonal movement calendar: Why did my cracks close up in the spring?: Spring is one of Oklahoma's wettest periods, and clay swells as it takes on water. A crack that closes has not necessarily been fixed; it may reopen the next time the soil dries.
Seasonal movement calendar: Does frost move foundations in Oklahoma?: Less than in northern states. Oklahoma winters are shorter and milder than the northern Plains, and the Oklahoma Climatological Survey describes frozen soil as infrequent, shallow and brief.
Seasonal movement calendar: Does the season affect foundation measurements?: Comparing measurements taken under similar soil moisture gives the clearest picture. Recording the season and current Mesonet soil moisture with each survey helps make later readings comparable.

Why did Oklahoma earthquakes increase, and can they damage houses?

Quakes rose sharply after 2009, mainly linked to deep disposal of oil-and-gas wastewater; moderate quakes can crack plaster and masonry.

What happened to Oklahoma's earthquake activity?: The Oklahoma Geological Survey (OGS) states that a large area of the state has had greatly increased seismic activity since 2009, and especially since 2013. The OGS describes these earthquakes as induced primarily by deep injection of produced water from oil and gas operations.
What are the largest recorded Oklahoma earthquakes?: Source: OGS top-ten list. Four of the state's ten largest listed events occurred in 2016.
Oklahoma induced earthquakes: How do magnitude and intensity differ?: Magnitude measures the energy released at the source. One number per earthquake; Intensity, on the Modified Mercalli Intensity (MMI) scale, describes shaking effects at a particular place. It varies with distance and ground conditions.
Oklahoma induced earthquakes: Where can the earthquake record be checked?: OGS earthquake catalogs: yearly lists of Oklahoma events.
Why do earthquakes matter for foundations?: In the moderate Oklahoma quakes, damage concentrated in masonry.
Why did Oklahoma start having so many earthquakes?: The Oklahoma Geological Survey links the increase to deep injection of produced water, the salty wastewater that comes up with oil and gas. Seismic activity increased greatly after 2009 and especially after 2013.
What is the largest earthquake recorded in Oklahoma?: The September 3, 2016 Pawnee earthquake. The Oklahoma Geological Survey's top-ten list gives it magnitude 5.8, while its initial fact sheet listed 5.6.
Oklahoma induced earthquakes: What level of shaking damages a house?: On the Modified Mercalli Intensity scale, level VI is described as minor damage such as falling plaster and a few cracks. Level VII, which the 2011 Prague earthquake reached, involves more significant damage.
Oklahoma induced earthquakes: How can I find out if an earthquake shook my area?: The Oklahoma Geological Survey publishes earthquake catalogs and a recent-earthquake map, and the USGS Did You Feel It? system collects reports from people to map shaking.
Is fracking causing Oklahoma's earthquakes?: Mostly no. The USGS says disposal of wastewater produced with oil is the primary cause, and only about 1 to 2 percent of Oklahoma earthquakes can be linked to hydraulic fracturing.
Are Oklahoma earthquakes still happening?: Yes, but far less often. The Oklahoma Geological Survey counted 15 earthquakes of magnitude 3.0 or greater in 2022, compared with 903 reported for 2015.

Why do Oklahoma foundations move, in plain English?

Most Oklahoma foundation movement comes from clay that swells when wet and shrinks when dry. Repair aims to stop damaging movement, not reach a level floor.

Foundations in plain English: Why does clay move like a sponge?: Picture the clay under a house as a stack of microscopic sheets. In the most active clays, water slips into the spaces between those sheets, and the soil swells; when it dries, it shrinks.
Foundations in plain English: Why is the house moving now?: Dry spells pull water out of the soil. Summer heat and drought dry the ground under homes, and one foundation repair contractor reported more calls during summer drought.
Foundations in plain English: Why is "level" not the goal?: No foundation is built perfectly level, and patios, porches and garages are often sloped on purpose for drainage. Engineers look at overall tilt (an even slope across the house) and deflection (bowing between two points), plus cracks and other damage, rather than a single number.
Foundations in plain English: What is a floor-level map?: An elevation survey measures the floor height at many points and draws lines connecting equal heights, like a topographic map.
Foundations in plain English: What is heave?: Not every problem is sinking. When water collects under a slab, the clay there swells and pushes that area up; this is heave.
Foundations in plain English: Why are piers paired with water control?: Piers carry the house down to firmer ground. Water control, including gutters, grading, drainage and moisture barriers, addresses the soil movement that caused the problem in the first place; engineers list both structural and non-structural repairs as options.
Foundations in plain English: How deep will the piers go?: In the Tulsa area, steel push piers usually stop around 12 feet; on one large logged job, half of the piers stopped between 9 and 14 feet, and the full range ran from 2 to 40 feet.
Foundations in plain English: What happens after the repair?: Lifting can disturb plumbing, so forensic engineers recommend plumbing tests after any lift and a new elevation survey as a baseline. See lifting procedure and restoration.
Foundations in plain English: Why does my house move with the weather?: Much of Oklahoma's soil contains clay minerals that soak up water between microscopic layers and swell, then shrink as they dry, so the ground under a house rises and falls with wet and dry periods.
Foundations in plain English: Why do foundation problems show up during drought?: Summer heat and drought dry out the soil under homes, which can make foundations shift; reported signs include new cracks, sticking doors and a gap between the soil and the house.
Foundations in plain English: My house is not level. Does that mean the foundation failed?: Not necessarily. Foundations are not built perfectly level, so engineers judge them by the pattern of tilt, deflection and damage rather than by a single high-to-low number.
Foundations in plain English: How deep do foundation piers go around Tulsa?: Oklahoma installation records show Tulsa-area steel push piers stopping at a median of about 12 feet, with half between 9 and 14 feet, though some go much deeper.

Why does a home addition crack away from the original house?

An addition is often a separate foundation at a different depth on different soil prep, so on Oklahoma clay the two move differently and crack at the joint.

Addition cracking at joint: Why do the two parts move differently?: Different foundation types. A slab addition attached to a crawl-space house, or a new slab poured beside an old one, rests on the soil in different ways; Different depths.
Addition cracking at joint: What are the signs at the junction?: A crack running along the line where old and new meet; A step or separation in the roofline or siding at the joint; A floor height change or door misalignment at the doorway between old and new rooms.
How are additions and mixed foundations repaired?: Supporting a shallow addition often means piers along the addition's perimeter down to firmer soil. See steel push piers and helical piers.
Addition cracking at joint: What about permits and disclosure?: Cities control permits for additions and repairs. In Tulsa, construction plans are required when damage is extensive or structural, as decided by the plans examiner.
Why is there a crack where my addition meets the house?: The addition and the original house often sit on different foundation types, depths and soils and were built decades apart under different codes, so they can move by different amounts as the clay underneath wets and dries.
Were older additions built to the same code as new ones?: Not necessarily. Oklahoma's current residential code requires two #4 reinforcing bars in all footings, a requirement added as an Oklahoma amendment, so footings built before these rules may have less reinforcing.
Do I need a permit to build or repair an addition?: Cities set permit rules. Tulsa, for example, accepts permit applications from owners, contractors, architects or agents and requires construction plans when damage is extensive or structural.
Should an addition be tied to the house or allowed to move separately?: Both approaches are used. One connects the two parts rigidly with support on both sides; the other gives the addition its own support and a flexible joint so each part can move without damaging the other.

Why does fill soil under a house cause settlement?

Poorly compacted fill, or fill with organic material or debris, can keep settling for years, often on one side of the house, apart from the seasonal pattern.

What is fill and why does it settle?: Fill is any soil, rock or debris placed by people rather than left in place by nature. On a sloping lot, builders often cut into the uphill side and push that soil to the downhill side to make a flat pad, a "cut-and-fill" lot.
What are the red flags for a filled lot?: These patterns are compared with seasonal clay movement on heave vs settlement, and the mechanism is described on fill consolidation settlement.
How is fill investigated?: Borings and lab samples are the direct way to see what is under a house.
What does fill mean for repair?: Piers have to pass through fill to reach native soil or rock that can carry the load; see steel push piers and helical piers; Settling fill can drag down on the sides of a pier, an added load engineers call downdrag; Interior slab areas over fill may continue to settle after the perimeter is supported; options include slabjacking and polyurethane and interior piers.
What is fill soil?: Fill is soil or other material brought in or moved during construction to level a lot or raise a building pad. How well it was chosen and compacted largely decides how it behaves under a house.
Why does a house on fill settle?: Fill that was not compacted in thin layers can squeeze down under the weight of the house and when it gets wet. The USGS lists hydrocompaction and drainage of organic soils among the causes of land subsidence.
Can clay be used as fill?: It often is, but highly expansive clay makes poor fill. An Oklahoma State University study rated Kirkland soil very poor as road fill because of its unstable, high shrink-swell material.
How is fill identified under a house?: Borings or hand-auger samples show what is below the slab. Debris such as brick, concrete, wood or trash in samples, or loose layers over native soil, indicates fill.

Why does some Oklahoma clay swell more than others?

Swelling depends mostly on clay minerals. Montmorillonite, a smectite, takes water between its layers and swells most; kaolinite swells much less.

What are clay minerals?: Clay minerals are microscopic, plate-shaped crystals built from layers of silica and alumina.
Clay minerals and swelling: What have Oklahoma studies found?: Soils on Permian red beds. In central and western Oklahoma soils formed from Permian shales, the fine clay was dominantly montmorillonite, with a mix of illite and montmorillonite, plus small amounts of kaolinite, in the coarser clay.
Can soil color show how much a clay will swell?: High-plasticity clays occur in both red and gray soils. Red Permian soils such as Kirkland are montmorillonite-rich, and a south Tulsa report on a site underlain by Nowata Unit shales found olive, brown and gray fat clay with plasticity indices up to about 39.
Clay minerals and swelling: Which lab tests stand in for mineralogy?: Mineral analysis is rarely run for a house. Engineers instead use index tests. The residential code treats soil as expansive when it has a plasticity index of 15 or more, more than 10% passing a No.
Clay minerals and swelling: How does mineralogy relate to chemical treatment?: Chemical treatments work on the clay itself. Forensic engineers list lime, cement, potassium and other chemicals among soil injection options. Oklahoma pavement research found that stabilizers react with soil particles to form cementing compounds that add strength.
What makes clay soil swell?: In 2:1 clay minerals such as montmorillonite (smectite), water is absorbed into the spaces between the mineral's layers, which is the main mechanism of shrink and swell; 1:1 clays such as kaolinite swell much less.
Is Oklahoma clay high in montmorillonite?: Many Oklahoma soils are. An Oklahoma State University study found the fine clay in Permian-derived soils of central and western Oklahoma was dominantly montmorillonite, and the Oklahoma Geological Survey reports that over 75% of the state's bedrock can produce expansive soils.
Clay minerals and swelling: Is the shale under my house as expansive as the soil?: Not always. A USGS study found Hennessey shale cored near Oklahoma City was mainly illite and kaolinite with low shrink-swell potential, though other studies have reported swelling and mixed-layer clays in the same units elsewhere.
Can lime treatment make clay swell?: Yes, when the soil is high in sulfate. Oklahoma research found lime added to a high-sulfate soil sharply increased swell because it formed the expansive mineral ettringite.
Can I tell how expansive clay is by its color?: No. Both red Permian clays in central Oklahoma and gray and brown shale-derived clays in south Tulsa have tested as highly plastic, so lab tests are used instead of color.