Short answer
Slab repair starts with a cause and a measurement, not a product. An engineer surveys floor elevations, checks drainage, trees and plumbing, then decides. Settlement is usually fixed with piers under the grade beams. Heave from swelling clay often is not, because common repair piers cannot hold a slab down. Moisture control is maintenance, not repair.
Key facts
- FPA recommends slab-on-ground tilt of 1% or less over the full length, width or diagonal, and deflection no worse than L/360.[1]
- The repair piers most commonly used on houses in the Houston area are not tied to the grade beams, so they cannot prevent uplift from heaving soil, per FPA.[2]
- Houston requires a permit for foundation repair, and slab-on-grade repairs need plans by a Texas-licensed engineer showing pier location, quantity and type.[5]
What counts as a slab foundation problem?
Every foundation on soil moves a little. NAHB notes that most foundations are designed for up to 1 inch of soil movement, and slabs on highly expansive soil can be designed for about 4 inches[3]. Movement becomes a problem when it causes distress you can measure.
The Foundation Performance Association (FPA), a Houston engineering group, sorts distress into three tiers[1]:
| Tier | What it looks like | Typical response |
|---|---|---|
| Architectural (cosmetic) | Cracks and separations you notice. They usually show at about 0.02 in in drywall and 0.04 in in concrete or brick[1]. | Patch after movement stops |
| Functional | Doors or windows that stick, will not close, or swing on their own; noticeable floor slope; tilted counters; trip-height offsets[1] | Engineer evaluation |
| Structural | A member can no longer carry its design load with an adequate safety margin[1] | Engineer-designed repair |
FPA's recommended limits for a slab-on-ground house are tilt of 1% or less over the full length, width or diagonal, and deflection no worse than L/360 (the span divided by 360)[1]. FPA says these criteria do not replace engineering judgment[1].
One catch: slabs are not built perfectly flat. FPA found most residential slabs are built within 1.0 inch of level[1]. A single elevation survey, with no earlier baseline, cannot prove how much a slab has moved since it was poured.
Many symptoms also get blamed on the foundation when something else caused them. FPA lists nail pops and trim gaps from wood shrinkage, doors binding on loose hinges, and brick cracks over undersized lintels[4]. See signs of slab foundation problems.
Step 1: Find the cause
A repair that ignores the cause tends to fail. FPA's repair committee says that in southeast Texas, foundation damage "is most often due to changes in moisture content of expansive soils"[2]. Common causes:
- Swelling and shrinking clay. Wet seasons lift the slab edge, droughts drop it. See expansive clay soil.
- Plumbing leaks under the slab. FPA lists broken sewer and water pipes as a cause of movement after repair[2].
- Poor drainage. Ponding water and downspouts that dump at the slab edge[2].
- Trees close to the house. Roots pull moisture from the soil under the slab edge[2].
- Frost. In Ohio and Illinois, freezing soil can lift shallow slabs and steps. See frost heave.
Step 2: Get an engineer's evaluation
FPA's guideline describes three levels of investigation[1]:
| Level | What the engineer does |
|---|---|
| A | Interview, walk-through, visual observations, factors affecting the foundation |
| B | Level A plus a floor elevation survey with contour plans, tilt and deflection math, and a documented baseline |
| C | Level B plus testing, such as soil sampling, a hydrostatic plumbing leak test, or concrete coring |
FPA's tilt and deflection limits need a Level B or C investigation to apply[1]. A free inspection by a repair salesperson is not the same thing. Ask who will design the repair, and whether you get the elevation survey in writing.
Step 3: Match the repair to the cause
| Cause found | Typical repair | What to know |
|---|---|---|
| Settlement (a section dropped) | Piers or piles under the grade beams, then lifting and shimming[2] | Piers must reach below the soil's active moisture zone[2] |
| Heave (a section rose) | Often not piers. Moisture control, or in some cases lowering high areas or lifting the whole floor above the soil's potential rise[2] | Common repair piers cannot hold a slab down[2] |
| Plumbing leak | Plumbing repair first, then reassess | Leveling can strain pipes; ask about a leak test before and after |
| Low interior area | Grout or foam injection under the slab[2] | Shallow repair; moves if soil moisture changes[2] |
| Drainage, trees | Gutters, grading, root barriers, watering | FPA classes these as maintenance, not repair[2] |
Pier types in one line each
FPA describes four common systems[2]:
- Steel push piers: steel pipe pressed down using the house's weight until it meets resistance or rock.
- Helical piers: steel shafts with helix plates screwed in until they reach a target torque.
- Pressed concrete piles: precast cylinders stacked and pressed in with the house's weight.
- Drilled concrete piers: a drilled hole filled with rebar and concrete, sometimes belled at the base.
Each has its own failure modes, such as too-shallow depth, piles that spring back if not shimmed right away, or unreinforced segments that shift sideways[2]. Read the pier types compared page before you compare bids.
Myth: piers make a foundation permanent
Piers support the slab against settling. FPA states that the piers most used for Houston-area home repairs "are not tied to the grade beams, and thus cannot prevent foundation uplift due to heaving soils," and that heave "is not generally considered to be a failure of the piers"[2]. If your problem is heave, a pier-only bid may not address it. A "lifetime" warranty may not cover it either. Read the exclusions.
Similar caution applies to steel lifespan claims. The helical pile standard that code evaluators use designs for corrosion over 50 years[8]. Claims of 100 years or more are not part of that basis.
Permits and engineers in launch-state cities
Rules are local. A few we verified:
- Houston: a foundation repair permit is required. Slab-on-grade repairs need plans by a Texas-licensed engineer showing pier location, quantity and type[5].
- San Antonio: the permit goes to the owner or a City-licensed residential building contractor. A Texas engineer of record designs or guides the repair and inspects it[6].
- Austin: foundation repair that adds no more than 128 sq ft of impervious cover can use an Express Permit, with a registered general contractor assigned[7].
For Ohio and Illinois cities, see the Ohio and Illinois pages. Ask your building department before work starts.
What to ask before you sign
- Who designed the repair? Is there an independent engineer's report with an elevation survey?
- Which pier type, how many, how deep, and what pressure or torque records will you get per pier?
- Will there be a final elevation survey and an engineer's letter after the work?
- Does the warranty cover heave? Is it transferable? Does it void if you skip watering or drainage upkeep?
- Will the plumbing be tested before and after leveling?
Costs depend on pier count and soil. See slab foundation repair cost and foundation pier cost.
When to call a pro
- Doors and windows begin to stick at the same time new cracks appear: call a structural engineer for a Level B evaluation.
- A floor slopes enough to notice, or a crack shows a vertical offset.
- You suspect a slab leak (wet spots, a rising water bill, warm floor areas): call a licensed plumber first.
- You have a repair bid but no engineer's design: get an independent engineer's review before you sign.
More questions
Can foam or mudjacking level a house slab?
It can lift low areas, but FPA calls both shallow repairs affected by active soil. If soil moisture changes, the slab can move again. Treat it as an engineer's decision, not a default.
Do I need an engineer, or can the contractor design the repair?
Several Texas cities require one. Houston wants engineer plans for slab repairs and San Antonio requires a Texas engineer of record. Even where it is optional, an independent engineer's report gives you a baseline and a design you can bid out.
Sources
- FPA-SC-13-1: Guidelines for the Evaluation of Foundation Movement for Residential and Other Low-Rise Buildings (Rev. 1, Apr 2015), Foundation Performance Association, Structural Committee. Accessed 2026-10-06.
- FPA-RC-01-0: Post Foundation Repair Performance of Residential and Other Low-Rise Buildings on Expansive Soils (Jan 2004), Foundation Performance Association, Repair Committee. Accessed 2026-10-06.
- Misconceptions about the common crack (Builder Education Series), National Association of Home Builders (Walt Keaveny, PE, PG). Accessed 2026-10-06.
- FPA-SC-03-1: Distress Phenomena Often Mistakenly Attributed to Foundation Movement (2004), Foundation Performance Association, Structural Committee. Accessed 2026-10-06.
- Foundation Repair permit (HPWFMO1010), Houston Permitting Center, City of Houston. Accessed 2026-10-06.
- Information Bulletin 172: Residential Foundation Repair (rev. Apr 7, 2025), City of San Antonio Development Services. Accessed 2026-10-06.
- Express Permits, City of Austin Development Services. Accessed 2026-10-06.
- AC358: Acceptance Criteria for Helical Pile Systems and Devices (published Apr 2025), ICC Evaluation Service. Accessed 2026-10-06.
Top Concrete Workers is an independent information service. We may be paid by contractors when we connect a homeowner with one; that never changes what we publish. Found an error? Tell us. We review safety and legal reports within 2 business days and all others within 7 days.