How Slabs Crack on Clay Soil
A concrete slab is rigid. When the red clay underneath it swells unevenly, usually because one side of the house gets more water than the other, the slab can't flex to match, so it cracks instead. Cracks that run in a stair-step pattern through brick or block above the slab are the clearest outdoor sign.
Poor drainage makes this worse. If gutters dump water right next to the foundation, or the yard slopes toward the house instead of away from it, that corner of the slab gets wetter than the rest and moves more.
Fixing a Settled Slab
The standard fix for a settled slab is underpinning: driving steel push piers or helical piers down past the unstable clay to load-bearing soil or rock, then using those piers to lift the slab back toward level. This is the same approach HomeAdvisor's 2026 cost guide lists as major structural repair, and it's typically the most expensive category of foundation work.
Smaller issues, like a single cracked slab section with no real settling, can sometimes be handled with epoxy injection or a smaller patch instead of full underpinning. A contractor should be able to tell you which category your house falls into after a visit.
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Take the free checkWhat to Ask Before You Sign Anything
Ask how many piers the job needs and where they'll go, since that's the main cost driver. Ask whether the quote includes any drainage work, since piering a slab without fixing the water problem that caused the settling often means doing it again in a few years.
Guthrie requires a permit for structural foundation work. A contractor pulling piers under your slab should be the one getting that permit, not you.
Questions
Is a cracked slab always serious?
Not always. A hairline crack with no gap and no movement over time is often just normal concrete shrinkage. A crack you can fit a coin into, or one that's growing, is worth a visit from a local pro.
How many piers does a typical slab repair need?
It depends on the size of the settled area and how far it's dropped. A small corner might need a handful of piers. A full-perimeter settling issue can need a dozen or more. A contractor will map this out on-site.
Can I pour a new slab instead of repairing the old one?
That's rarely necessary and almost always far more expensive than underpinning. Most slab problems are fixable by stabilizing and lifting the existing slab.
Will fixing the slab stop the cracks in my brick above it?
Lifting the slab usually stops the cracking from getting worse, but it won't erase cracks already in the brick or siding. Those are typically patched separately after the slab is stable.