Cracks in Brick, Drywall and Slab: Sealing or Something More
Foundation crack repair is the cheapest line on most bids and the easiest to get wrong, because sealing a crack that is still moving just makes a tidier crack. With clay that shifts from season to season, the order matters: find out whether it is still moving, deal with that, then close it.
Fixr's 2026 guide prices crack sealing and epoxy injection at $200–$1,000, and This Old House lists crack filling at $250–$800. Brick and drywall repairs are priced separately. If the crack comes from a slab that is still settling, pier work comes first, at $1,000–$3,000 per pier.
Reading the crack
- Hairline cracks in a slab, found under carpet or tile, are common from concrete shrinking as it cured. On their own they are rarely structural.
- Stair-step cracks in brick follow the mortar joints and usually mean the slab under that wall has moved up or down.
- Vertical brick cracks wider at the top or bottom show which way that section is tipping.
- Diagonal drywall cracks from the corners of doors and windows point to the frame twisting as the floor shifts.
- Broken slab corners under the brick ledge are often cosmetic, though worth sealing against water.
Is the crack still moving?
Pencil a short line across each end of the crack, write the date beside it, and take a photo with a ruler in the frame. Check again every few weeks through a full season. A crack that opens through the hot, dry stretch of July and August and narrows after the wetter fall months (NOAA 1991–2020 normals) is following the clay; the official description of Houston Black clay notes dry-season soil cracks up to 4 inches wide (USDA NRCS). One that only grows is the more urgent kind, especially if doors nearby start to stick.
Ways a foundation crack repair gets done
- Epoxy injection glues a dry concrete crack shut and restores some strength.
- Polyurethane injection stays flexible and suits cracks that seep water.
- Brick repointing rakes out cracked mortar and replaces it; broken brick is cut out and replaced to match.
- Drywall repair means tape and joint compound, best left until movement has stopped.
- Sealing slab edges and corners keeps rainwater from running under the foundation.
When a crack means the slab needs piers
Cracks that keep widening, show up on both the inside and outside of the same wall, or come with sloping floors and binding doors usually mean the foundation itself has moved. Sealing them first wastes money. Read about house leveling with slab piers, then compare prices for both kinds of work in the San Antonio repair cost table.
Questions homeowners ask
Can I fill brick cracks myself?
You can, but wait until you know the wall has stopped moving, or the new mortar will crack along the same line. Match the mortar color, and never caulk over a crack you are still tracking; you will lose the record of whether it is growing.
Have someone look at the house
Tell us what you have noticed and where: the crack, the door, the floor. One independent foundation specialist who works in San Antonio will phone you to talk it over and set a time to see it.