Foundation repair · LaCoste, TX
Foundation repair in LaCoste, where flat ground keeps the water against the slab.
LaCoste, which the post office spells La Coste, is a small Medina County farm town west of San Antonio, and the soil survey maps almost all of it as one thing. Knippa clay covers 92 percent of the ground under the 78039 ZIP, and the map unit it belongs to is named for a slope of zero to one percent. For a foundation, that slope figure matters as much as the clay number does.
The housing is modest older homes in town and newer construction on the acreage around it, and both sit on the same flat dark clay. Our free inspection answers two questions. How far the floor has actually moved, and whether the rain leaves this lot or soaks in where it lands.
LACOSTE AND THE MEDINA COUNTY FARMLAND AROUND IT, THE TOWN CORE OUT TO THE ACREAGE LOTS AND THE COUNTY ROADS TOWARD CASTROVILLE, ABOUT FORTY MINUTES WEST OF OUR VANCE JACKSON SHOP.
What the USDA maps here
The USDA maps the dominant soil under LaCoste as Knippa, high shrink–swell (linear extensibility ≈ 7.2%). Knippa is a dark calcareous clay sitting over limestone bedrock. It carries real seasonal movement, and because the rock is not far down there is little depth for water to disperse into, so flat ground holds moisture at the surface longer.
See the Knippa soil series at USDA →What we see in LaCoste
The local patterns, specifically.
Water that soaks in instead of running off
On ground mapped at zero to one percent slope, a storm does not drain away from the house. It sits, soaks in and keeps one stretch of slab edge wetter than the rest for days. That uneven moisture is the most common thing we write up in LaCoste, and it is usually the cheapest finding to act on.
A moderate swell number that still moves a slab
Knippa clay reads 7.2 percent linear extensibility, well short of the 12 percent clays east of here. Movement comes slower and smaller on this ground, which means damage tends to accumulate quietly across several years rather than announce itself in one dry summer.
Shallow limestone under the clay
Knippa is clay over rock, not clay over more clay. Bearing strata are comparatively close to the surface, which keeps pier drives short, and it also means the whole soil profile above that rock is the part responding to the weather.
Slabs added onto farm houses
Carports, shop bays, patios and room additions get poured against the original house out here, often years apart and on different footings. Those joints crack first, and the crack usually marks two slabs moving at their own rates rather than a foundation in trouble.
The ground under LaCoste
Knippa clay on ground the soil survey maps at zero to one percent slope.
The soil survey leaves little ambiguity here. A single series, Knippa clay, covers 92 percent of the ground mapped under the LaCoste ZIP, with small Montell and Castroville components filling the rest. Knippa is a dark calcareous clay formed over limestone, and the survey puts its linear extensibility at 7.2 percent. Linear extensibility is the plain measure of how far ground swells when it wets and shrinks when it dries. At 7.2 percent that is real movement, enough to lift and drop a slab edge across a season, but it is well short of the 12 percent Blackland clays that run under much of San Antonio. Knowing the number changes what a crack means. On this ground a hairline that has not grown through two full seasons is usually finished.
The slope figure is the part homeowners here underestimate. The USDA names this map unit Knippa clay, zero to one percent slopes, which is another way of saying the ground is flat. Flat ground does not shed water. A storm that would run off a Hill Country lot in minutes soaks in where it lands and stays in the top of the profile for days, and the clay closest to the slab edge holds it longest. That is the mechanism behind most of what we measure out here, and it is why poor drainage does more slab damage than the clay itself in a town shaped like this one. Downspouts extended well clear of the wall, the first few feet of soil pitched away from the slab, and drainage corrected where a lot has gone flat against the house are the first three things we recommend, and on a good number of LaCoste houses they are the whole of it.
Three grounds inside a short drive
LaCoste, Castroville and Rio Medina do not share a soil.
It is tempting to treat eastern Medina County as one place. The soil survey does not. Our foundation risk map scores the LaCoste ZIP at 54 out of 99, the Elevated band, on a scale built from linear extensibility. Castroville, a few miles northwest, scores 56 on ground deposited by the Medina River, where part of town carries a flood classification and the foundation conversation starts with water rather than swell. Rio Medina, north of both, sits on Monteola clay at 15.8 percent and scores 97, the High band, more than twice the swell range of LaCoste through the same wet and dry year. Three towns a short drive apart, three different reasons a floor goes out of level.
That is why we do not quote a repair off a town name. The floor elevation survey comes first everywhere, and the number it produces means something different depending on which of those grounds the house sits on. A quarter inch of fall across a LaCoste living room on flat Knippa clay, with the roof water dumping at one corner, is a drainage finding. The same quarter inch on Rio Medina's Monteola is a different conversation entirely. Settlement and heave look alike on a floor plan and call for opposite work, and what separates them reliably is a measured map of the floor read against what the soil under it is known to do.
What a repair looks like here
Shallow rock keeps LaCoste pier work short and the scope narrow.
Because Knippa clay sits over limestone, the load-bearing strata under a LaCoste house are comparatively close to the surface. We install steel piers and hybrid piers only, both pressed to refusal on that bearing layer, and either one runs $600 to $1,000 per pier installed. The pier count comes off the elevation survey rather than off a walkthrough, which is why the free inspection is the estimate instead of a lead-in to one. Every pier we set carries a lifetime transferable warranty that stays with the house when it sells, and we return for a performance follow-up inspection each year afterward.
The more useful fact for a LaCoste homeowner is how often none of that is needed. About a third of the inspections we run end with no repair recommended, and on flat Knippa ground that share is where the drainage findings land. ICC-certified inspectors take the readings, write them down and hand them over whether or not there is work in it. If you want the measurements before you want a bid, that is exactly what the visit produces.
Neighborhood by neighborhood
LaCoste foundation repair, street level.
The LaCoste town core
The older, smaller lots in town hold the oldest slabs in this service area, and most of them found their level decades ago. On ground this flat a yard often has no grade except what the lot line and the street give it, so the first thing we answer here is where the roof water goes once it reaches the ground.
Acreage lots outside the city limits
Newer rural construction sits on built-up pads over native Knippa clay. The seam where a placed pad meets undisturbed ground is where the first cracks show, usually at a garage return or a porch corner, and usually in the first dry summer after the house is finished.
The farmland northwest toward Castroville
Between LaCoste and Castroville the Knippa flats start giving way to the river-deposited ground of the Medina valley. Where a lot straddles that change the two soils do not move at the same rate, and the elevation survey picks that up as a tilt across the house rather than a dip at one corner.
The flats south of town
Open farm country on the same zero to one percent ground, with houses scattered along the county roads and shops, barns and added slabs poured up against them. Field runoff crosses these yards slowly instead of leaving them, so grading and gutters carry more of the answer out here than piers do.
Our work near LaCoste
Real foundation repair across LaCoste and the corridor.
Costs, warranty and inspections
The straight numbers on foundation repair in LaCoste.
Your nearest Motmot office
San Antonio (Main Office)
4402 Vance Jackson Rd Ste 206, San Antonio, TX 78230. Call or text (210) 816-0034.
Our main shop at Vance Jackson and Loop 410 runs the San Antonio metro daily and covers the I-35 corridor north to the Austin line.
Available in LaCoste
Our full service list, available across the corridor.
LaCoste specifics
Asked by LaCoste homeowners.
From the Learning Center
Reading for LaCoste homeowners.
LaCoste sits in Medina County. The county page carries the USDA soil survey for the whole county, the series names and swell numbers, and how the ground changes from one side of it to the other.
Foundation repair across Medina County →Nearby
Also serving the communities around LaCoste.
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