What are stem wall and grade beam foundations?

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

In short: A stem wall foundation is a short wall built on a continuous footing, used under crawl spaces, on sloped lots and around some slabs. A grade beam foundation is a concrete beam spanning between drilled piers that reach below the clay that swells and shrinks, with a gap under the beam so the clay cannot lift it. Both can move in Oklahoma clay, but for different reasons.

What is a stem wall on a footing?

A footing is the wide concrete base that spreads the house's weight onto the soil. A stem wall is the vertical wall of concrete or masonry that rises from it.

• Footing size: code minimum 12 in wide and 6 in thick, with larger sizes from the code tables for heavier loads ¹.
• Footing depth: at least 12 in below the ground surface, and below the frost line where frost applies ¹.
• Sloped lots: footing bottoms may slope up to 10%; steeper ground requires stepped footings with level tops ¹.
• Reinforcement where the code's seismic provisions apply: vertical No. 4 bars at no more than 4 ft, hooked into the footing and extending at least 14 in into the wall, plus a horizontal No. 4 bar within 12 in of the top ².
• Oklahoma additions: the state's 2024 code adoption adds two No. 4 bars to all footings and requires cold joints between footing and stem wall to be tied with No. 4 bars at each corner, no more than 6 ft apart, with 12 in of embedment ³.
• Anchor bolts: at least 1/2 in diameter, no more than 6 ft apart and embedded at least 7 in, tying the wood sill to the wall ⁴.

A cold joint is the seam where concrete poured on one day meets concrete poured later, such as a stem wall cast on a footing that has already set.

What is a grade beam on drilled piers?

A drilled pier is a concrete column cast in an augered hole. A grade beam is a reinforced concrete beam that spans from pier to pier at the ground surface and carries the walls.

Engineering guidance for swelling soils describes this system as the general choice for moderately to highly swelling soils ⁵:

• Piers extend well below the zone of seasonal moisture change ⁵.
• Piers are anchored in non-swelling soil to resist uplift, by belled bottoms, grooved holes or extra depth ⁵.
• A gap of 3 to 6 in is left between the soil and the grade beam so swelling soil cannot push up on it ⁵. Cardboard void forms that hold this space during the pour are commonly called void boxes.

Drilled piers have been used for houses on expansive soil in California, Colorado and Texas since the late 1950s ⁷. Seasonal moisture change can extend from 3 to 40 ft deep, and the upper part of a pier can lose contact with the soil as clay shrinks ⁷.

How do these foundations fail?

When piers move after construction or repair, the mechanism is covered in pier uplift or movement after repair. Underpinning brackets bear on the stem wall or grade beam itself; spacing and load questions are covered in loads, pier spacing and capacity.

How are these foundations repaired?

• Deeper or belled supports: drilled bell-bottom piers
• Steel underpinning on the stem wall: steel push piers or helical piers
• Moisture control around the perimeter: drainage and root barriers
• Mixed foundations where an addition meets the original house: additions and mixed foundations

Related

• Drilled Bell-Bottom Piers
• Pier and Beam Crawl Space
• Pier Uplift or Movement After Repair
• Loads Pier Spacing and Capacity
• Shrink-Swell and Active Zone