Why did a 1970 Claremore slab house on a sloped lot crack everywhere?

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

rural Claremore area20251-story timber frame, brick veneer and fiber siding, built about 1970; garage converted to living space; patio addition on the eastslab-on-grade with continuous perimeter footings and stem walls; HVAC ducts under the slab

In short: A 1970 slab-on-grade house near Claremore, on a lot sloping moderately to steeply east, had misaligned doors, cracks through the interior and veneer cracks on every exterior wall ¹. The engineer attributed the movement to variations in moisture content of the soil beneath the footings and slab. The scope was piers under the perimeter footings, polyurethane slab leveling, a plumbing leak test and crack stitching ¹.

What did the house show?

The engineer inspected the house in December 2025 ¹. It is a one-story timber-frame house with brick veneer and fiber siding, built about 1970. The garage had been converted to living space and a patio addition abuts the original east wall. The foundation is a slab-on-grade with continuous perimeter footings and stem walls, and HVAC ducts run under the slab ¹.

Observed conditions ¹:

• The site slopes moderately to steeply down to the east on the front, back and both ends.
• Representative doors were misaligned and hitting the top and side of the frame.
• Significant interior cracks throughout, with stem-wall-to-slab and baseboard separations in many areas.
• About a 1 in. gap between the ceiling and the fireplace veneer.
• Veneer cracks and veneer-to-trim gaps on all exterior walls.
• Floor elevations were not measured as part of the inspection.

What did the engineer find was causing it?

The engineer attributed the movement to "variations in the moisture content of the soil beneath the footings and slab," describing the soil at foundation level as a mildly active clay ¹. The report also noted the steep slope and the additions, but did not name them as the cause ¹.

What repair was specified?

• Piers under the continuous footings at locations shown on the engineer's drawing ¹.
• Polyurethane slab leveling where the slab is out of level. The exact areas are to be set by the contractor from a floor survey. The engineer cautioned about sub-slab plumbing and ducts and against lifting large areas over plumbing ¹.
• A leak test of supply and drain lines by a licensed plumber, with any leaks repaired ¹.
• After leveling, stitch slab cracks with carbon fiber strips and self-leveling epoxy. Where a height difference remains, saw-cut 6 in. or more each side and re-pour ¹.
• Tuck-point mortar joints (raked at least 1/2 in. deep) and caulk veneer-to-trim joints with silicone ¹.
• Delay cosmetic repairs several weeks after stabilization ¹.

What does this case show about Oklahoma foundations?

• Clay subsoils formed from shale are common here. The USDA describes the Dennis series, whose type location is in Rogers County, as formed in residuum weathered from Pennsylvanian shale. Its subsoil is silty clay or clay with 28 to 50 percent clay, and a perched water table sits 12 to 30 inches deep from December through April in normal years ². This record does not identify the soil series at this site. The series shows the kind of clayey, seasonally wet subsoil found in the area.
• Uneven moisture causes more damage than uniform moisture. ASCE's homeowner guide explains that clay swells when it gains water and shrinks when it dries, and that uneven moisture changes do more damage than uniform ones. It also notes that sewer or water line leaks can cause localized movement ³. That is why the engineer paired lifting with a plumbing leak test ¹.
• Slopes and additions complicate the picture. On this house the steep east slope and two additions were noted alongside the clay ¹.

Related

• Slab on Grade
• Steel Push Piers
• Slabjacking and Polyurethane
• Plumbing Leak Detection and Repair
• Additions and Mixed Foundations
• Dennis soil series