Why did a Bixby engineer want a tree removed before piering a corner?

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

Bixby20251-story wood frame, stone veneer, attached 2-car garageSlab-on-grade (floating slab) with continuous perimeter footings and stem walls

In short: A Bixby slab home had veneer separations and cracks all around, largest at the northeast corner, where a tree stood. The engineer named active clay soil and the tree as the causes, and specified removing the tree first, then underpinning that corner with 3 steel piers at least 10 ft below the footing ¹.

What did the house show?

• Stone veneer separations and hairline to 1/4 in. cracks, some previously patched, around the chimney and on the north, south and west walls. The largest were at the northeast corner ¹.
• Cracks in a garage wall and stem wall, and garage slab cracks rated non-structural ¹.
• Interior cracks at the northeast and southeast corners and in a bedroom closet, and uneven floors ¹.
• A tree close to the northeast corner, photographed in the report ¹.
• Slab movement judged not severe enough to repair ¹.

What did the engineer find was causing it?

Shrink-swell movement of active clay soil, with the tree at the northeast corner as a contributor. No soil report was available ¹.

What repair was specified?

1. Remove the tree at the northeast corner ¹.
2. Then underpin the northeast corner with 3 piers, shown at about 9 ft spacing on the plan ¹.

The engineer's standard pier specification applied: steel piers only unless the engineer approved another system; each pier to penetrate at least 10 ft below the bottom of the foundation to firm, stable strata, with the detail reading "drive to refusal — bedrock (blue shale)"; a log for every pier listing depth, type, diameter, driving pressure and lift; mortar removed from patched cracks near piers before lifting; a 6 x 6 x 1/2 in. angle iron under the footing where a pier lands near a crack; and a call to the engineer if old shallow concrete piers were found. Pier locations and count could change to suit footing conditions. A repair inspection by the engineer was available on request ¹.

What does this case show about Oklahoma foundations?

On clay soils, trees draw water out of the ground beneath nearby foundations during dry spells, the clay shrinks, and the result is settlement with cracking that often shows around windows and doors ². Tree roots are unlikely to break sound footings directly; the damage comes from the soil drying ². Below the depth that weather alone dries out, a tree's water demand can be the main driver of shrink and swell in clay ³. In this house the worst cracking was at the corner next to the tree ¹.

The engineer listed the tree removal ahead of the piers ¹. Published guidance also notes that, in rare cases where clay has been kept dry at depth for years, removing a tree can let the soil re-wet and heave ².

Only one corner was piered. Cracks elsewhere were smaller and the slab movement was judged not severe enough to repair, so the specified underpinning was limited to the corner next to the tree ¹.

Related

• Trees and Roots
• Tree Management
• Tree-Root Desiccation Settlement
• Post-Tree-Removal Heave
• Steel Push Piers
• Slab on Grade