How is foundation movement monitored in Oklahoma?

Reviewed by Preston, Oklahoma foundation repair consultant · Updated 2026-10-14

In short: A monitoring program measures a foundation repeatedly over months to learn whether it is still moving, which direction it is moving, and whether the movement follows the seasons. Engineering guidelines call for at least a year of readings, because repairs made after movement has stopped are less likely to see distress return ¹. In Oklahoma's expansive clays, monitoring is often the first step when a slab may be heaving rather than settling.

What is a monitoring program?

Monitoring is observation, not a repair. It combines three kinds of records taken on a schedule:

• Floor elevation surveys — relative heights measured at the same marked points on each visit ¹.
• Crack and distress records — new or widening cracks, sticking doors and similar signs noted on a plan of the house ¹³.
• Moisture and rainfall records — soil moisture, rainfall and drainage conditions around the foundation, so movement can be matched to weather ¹.

The goal set out in engineering guidance is to determine whether excessive movement is happening, whether it has likely stopped, and why it happened ¹.

Why does monitoring matter on Oklahoma clay?

Expansive clay swells when wet and shrinks when dry. The depth where this seasonal moisture change happens is called the active zone. A study using Oklahoma Mesonet field data estimated active zone depths across the state at roughly 0.5 to 4 meters (about 1.5 to 13 feet), with shallower soil reacting most to weather ⁷.

Because the soil moves up and down with the seasons, a single visit can mislead. A slab edge that looks low in a dry August may rise again after spring rain. Monitoring separates two patterns ¹:

This is why monitoring is often the first step for perimeter wetting heave, post-tree-removal heave and leak-related heave: the soil may need time to reach moisture balance before anyone can tell what, if anything, needs lifting. See heave vs settlement for how the two are told apart.

How are the measurements taken?

Elevation surveys

• Readings are taken about every 30 to 100 square feet, including room corners and near heavy loads such as masonry fireplaces ².
• The instrument should read to about 1/8 inch or better; a spirit or carpenter's level is not considered accurate enough ².
• Each survey uses the same points and the same reference point so that a "time-change" plan (later reading minus earlier reading) can be drawn ².
• A benchmark is a reference assumed not to move. Guidelines warn that trees, curbs and manhole covers usually make poor benchmarks ¹.
• Manometer-style levels are accurate to about ±0.1 inch, and operator error can add about ±0.1 inch more, so isolated changes of about 0.2 inch may fall within measurement error unless nearby points or new cracks agree ¹.

More on the method is in elevation surveys.

Crack monitoring

Simple gauges show whether a crack is still active. Federal preservation guidance describes three approaches: two pencil marks on tape across the crack measured on a schedule, a glass slide epoxied across the crack that breaks if movement continues, and a two-plate sliding crack monitor with a printed scale ³. Measurements are charted at regular intervals and kept on file with photographs ³. Seasonal opening and closing is covered in cracks that open and close seasonally.

Soil moisture records

The Oklahoma Mesonet reports soil moisture at most of its stations at depths of 2, 4, 10 and 24 inches ⁴. Its Fractional Water Index runs from 0 (near the wilting point, very dry) to 1 (near field capacity, wet) ⁴. The Mesonet website publishes daily values and graphs of recent readings ⁴⁵. Recording the nearest station and its reading with each survey lets a later reader see whether the soil was wet or dry at the time. See Mesonet for foundation pros.

How often are readings taken and when is movement stable?

Guidelines from a Texas engineering group working on similar expansive clays set out these points ¹:

• Monitor for at least one year.
• Complete at least three time-change surveys, with the first and last in the same season.
• Ideally, record elevations every three months.
• Correct drainage, plumbing leaks and other moisture sources at least six months before the monitoring period being judged.

The same guidelines treat movement as generally stabilized when the largest differential change is about 0.3 inch or less over three to four months (0.4 inch or less over six to eight months), no new functional or structural distress appears, and the movement lines up with climate and rainfall ¹. The authors note the guidance was written for Southeast Texas and should be applied with care elsewhere ¹.

For ongoing homeowner checks, a companion guide suggests inspecting the site and structure twice a year and after extreme wet or dry weather, comparing results with earlier photos and records ⁶.

What are the limitations of monitoring?

• Monitoring takes at least a year and only shows whether movement has stopped; it does not stop movement itself ¹.
• Results depend on repeating the same points, the same reference and comparable instruments ².
• Newly built foundations commonly go through a 12- to 24-month adjustment period, which can look like movement ².

Related

• Elevation Surveys
• Seasonal Movement Calendar
• Heave vs Settlement
• Tolerances and Standards
• Mesonet for Foundation Pros
• Drought and Wet Cycles