Home / Slab Foundation Repair
Most homes in Boerne and the surrounding Hill Country sit on a concrete slab poured directly on the ground. When the soil under one part of that slab changes, the slab moves with it, and the fix starts with finding out why.
A slab-on-grade foundation is a single concrete pour with thickened edges and interior grade beams that sit right on the prepared ground. There is no crawl space and no basement, so every inch of that slab depends on the soil beneath it staying put. In Kendall County that soil is often a thin layer of clay over caliche and limestone, and the depth to rock can change from one corner of a lot to the other. That uneven support is why one end of a slab can stay rock-solid while the other end drops.
Many homes built in Texas over the last few decades, including a lot of the newer subdivisions around Boerne, use post-tension slabs. Steel cables (tendons) run through the concrete in both directions and are stretched tight after the pour, which squeezes the slab together so it acts more like one stiff plate. That design resists cracking well, but it changes how a repair is done. You cannot drill or core through a post-tension slab without knowing where the tendons are, because cutting a tensioned cable is dangerous and weakens the slab. Look for a stamp or sticker near the garage that says the slab is post-tensioned, and ask any contractor how they will locate tendons before they cut. Piers on a post-tension slab are usually installed from the outside perimeter, and interior work is planned around the tendon layout.
Slab leaks are worth their own mention because they get confused with foundation failure in both directions. A leaking sewer or supply line under the slab can cause heave (a bulge in the floor) or settlement, and fixing the foundation without fixing the leak means the soil keeps changing. Signs include a water bill that climbs for no reason, a warm spot on the floor, the sound of running water when everything is off, or damp flooring with no obvious source. A licensed plumber can run a pressure test or a camera line before any foundation work starts. If a leak is found, it should be repaired first and the soil given time to settle out before a lift is planned.
The usual repair is underpinning: piers installed at the perimeter beam (and sometimes interior beams) down to a firmer layer, then the slab is lifted in controlled stages back toward level while elevations are watched across the whole house. The type of pier matters, and the options and tradeoffs are laid out on the foundation leveling and piering page. A slab will rarely come back to perfectly flat. The goal is to bring it within a reasonable tolerance and stop further settlement in the areas that were piered.
Most post-tension slabs have a stamped warning or a sticker near the garage door or in the garage itself. You may also see small patched pockets along the slab edge where the tendons were anchored. If you are unsure, the builder or the original plans will say, and a contractor should confirm it before any drilling.
Nearly all residential slab problems are repaired by underpinning and lifting, not replacement. Full replacement is rare and usually only discussed when a slab is badly broken up. Our guide on foundation repair vs. replacement walks through the difference.
Lifting often closes many cracks partway and gets doors working again, but it rarely makes drywall look new. Expect some patching and paint after the lift. Cracks in brick may tighten up but usually still need a mortar touch-up.
The biggest drivers are the number of piers, the pier type, and how deep stable bearing is on your lot. A written plan should list each of those. Our Texas foundation repair cost guide explains the cost drivers in more detail.
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