Foundation repair · Comal County County, TX
Anhalt clay swells 16.1 percent in Comal County and then stops on limestone 28 inches down, so the movement happens close to the surface.
If your house is in Comal County, the first thing that matters is which side of the Balcones Fault Zone you are standing on. Northwest of it you are on Edwards Plateau limestone, with pockets of clay that swells up to 16.1 percent sitting in shallow upland flats over rock that is sometimes less than two feet down. Southeast of it you are on deep blackland clay with no rock to bear on at all. Same county, same rainfall, two completely different failure patterns and two different repair plans.
The ground under Comal County County
The Balcones Fault Zone runs right under New Braunfels
The Balcones Fault Zone crosses Comal County from northeast to southwest, and seven main faults of that system cross the county (George, Geology and Ground-Water Resources of Comal County, https://digitalcommons.usf.edu/kip_articles/2353/). Northwest of that line is the eastern edge of the Edwards Plateau. The bedrock is Glen Rose Limestone of the Trinity Group with the Edwards Group above it, and the Glen Rose weathers into its diagnostic bench and slope stair-step because it is built of alternating beds of hard limestone and dark blue marl. The marl beds are the soft, moisture-sensitive layers. The Edwards and Glen Rose limestones belong to the Comanche Series, which reaches a maximum thickness of about 1,900 feet in this county. That is the ground under Bulverde, Spring Branch and Canyon Lake, where Anhalt and Tarpley clays sit as residuum in the upland flats over shallow limestone while Comfort, Brackett, Real, Rumple and Eckrant cover the slopes with a foot or so of rocky soil. Between the two halves runs a thin band of the post-Edwards section, Georgetown Limestone, Del Rio Clay, Buda Limestone, Eagle Ford Shale and Austin Chalk. Del Rio Clay and Eagle Ford Shale are the soft, swelling units in that stack, and faulting drops them into narrow outcrop strips, so a subdivision can straddle a hard limestone block and a clay or shale block within the same street. Southeast of the escarpment the outcrop belt is poorly exposed shelf limestone, argillaceous limestone, marl, claystone and mudstone of the Cretaceous Taylor and Navarro Groups and the lower Tertiary Midway Group. Those marls and claystones weather into vertisols, which is where Houston Black, Heiden, Branyon and Ferris come from. That is the ground under the eastern side of New Braunfels and out toward Selma, Schertz and Garden Ridge.
Up on the plateau above the escarpment
Nearly level to gently sloping flats at 0 to 3 percent slopes, carrying Anhalt and Tarpley clay as residuum over weathered Glen Rose limestone and chalk. Anhalt hits fractured limestone at 71 to 74 cm, which is 28 to 29 inches, and Tarpley hits hard limestone at 43 cm, which is 17 inches. What fails here is the difference inside one footprint. Piers reach competent rock quickly, but a slab edge sitting over clay that swells 13 to 16 percent lifts and drops with the season against an interior that is bearing on rock and barely moving. You get corner-to-corner differential in a house that never sat on uniform ground to begin with.
The canyon slopes running down toward the Guadalupe
Comfort, Brackett, Real, Rumple and Eckrant cover the plateau slopes with roughly a foot of rocky soil over hard limestone. Comfort runs 45 to 65 percent clay but a maximum linear extensibility of only 3.2 percent, because the series is clayey-skeletal and so full of rock fragments that there is very little fine material left to swell. So swell is not the main enemy on these lots. What fails here is water and grade. Storm runoff moves fast across shallow soil and rock, undercuts footings and perimeter beams, and works on any fill placed to make a level pad on a hillside. This is drainage correction, french drain and crawl space work more than pier work.
The fault seam under New Braunfels
The post-Edwards section, Georgetown Limestone, Del Rio Clay, Buda Limestone, Eagle Ford Shale and Austin Chalk, is thin but faulting drops it into narrow bands across the middle of the county. Del Rio Clay and Eagle Ford Shale are the swelling members of that stack. What fails here is unpredictable from the street. Two houses in the same phase of the same subdivision can sit on a hard limestone block and a clay or shale block, and they will need different pier depths and different counts. This band is the reason we probe rather than quote off a floor plan.
The prairie floor southeast of the escarpment
Houston Black, Heiden, Branyon and Ferris, weathered out of Taylor, Navarro and Midway marls and claystones. Houston Black has no bedrock restriction recorded at all and Branyon's solum runs past 203 cm, which is 80 inches, so there is nothing shallow to bear on. What fails here is classic deep-clay heave and settlement, with Branyon cracking 2.5 to 8 cm wide, which is 1 to 3 inches, and holding those cracks open 90 to 150 days in most years. Pier depth is driven by finding load-bearing strata rather than by hitting refusal, so piers go deeper and cost more per house than on the plateau side. Where Heiden sits on 3 to 8 percent slopes, downhill creep and edge drop stack on top of the seasonal movement.
Straight from the soil survey
What the USDA maps under Comal County County.
USDA publishes soil at the county level, which is why this page exists and why a city page cannot carry it. Comal is published jointly with Hays as survey area TX604, Comal and Hays Counties, Texas, so every acreage figure below covers both counties rather than Comal alone. The values are representative SSURGO values pulled from USDA NRCS Soil Data Access at https://sdmdataaccess.sc.egov.usda.gov/. The column to read first is linear extensibility, the percent a sample changes in length between wet and dry. The higher that number, the more your ground moves between a wet spring and a dry August. Note that the most extensive soil in the survey area is also one of the least expansive, and the most expansive one on the plateau side has hard rock right underneath it. That combination is what makes this county awkward.
| Soil series | Share of county | How much it swells | What that means for a foundation |
|---|---|---|---|
| Comfort | Comfort-Rock outcrop complex, 1 to 8 percent slopes, 153,688 acres in survey area TX604, and also a named component of Brackett-Rock outcrop-Comfort (110,380 acres), Rumple-Comfort rubbly association (106,383 acres) and Real-Comfort-Doss (44,224 acres) | LEP ≈ 3.2% | Roughly a foot of rocky soil, 30 to 33 cm to lithic bedrock, sitting on hard limestone, so a pier finds rock almost immediately and the real threats to the structure are runoff, erosion under the footing and slope movement rather than swell. |
| Heiden | Heiden clay 3 to 5 percent slopes eroded, 15,732 acres, plus 1 to 3 percent slopes at 7,444 acres and 5 to 8 percent slopes eroded at 4,585 acres | LEP ≈ 12.2% | High swell on sloping ground derived from Taylor Group marl, with densic material at 112 to 147 cm, so seasonal heave gets compounded by downhill creep and a dropping edge on the low side of the house. |
| Houston Black | Houston Black clay 1 to 3 percent slopes, 20,463 acres, plus Houston Black gravelly clay 3 to 8 percent slopes at 4,526 acres | LEP ≈ 12% | Deep clay at 54 to 55 percent with no bedrock restriction recorded, so the slab heaves and settles with nothing shallow to bear on and pier depth is set by finding load-bearing strata instead of hitting refusal. |
| Branyon | Branyon clay 0 to 1 percent slopes, 13,066 acres, plus 1 to 3 percent slopes at 4,892 acres | LEP ≈ 13% | Very deep, very active clay on flat ground, solum past 203 cm with cracks 2.5 to 8 cm wide that open from the surface down to 51 cm or more and stay open 90 to 150 days in most years, which is the worst case for an unreinforced slab. |
| Tarpley | Tarpley clay 1 to 3 percent slopes, 5,833 acres, the largest single Anhalt or Tarpley unit in the survey area | LEP ≈ 13.6% | Under a foot and a half of clay at 45 to 65 percent, then hard limestone at 43 cm, so piers reach rock fast while the slab edge over the clay keeps lifting and dropping against an interior that is nearly fixed. |
| Anhalt | — | LEP ≈ 16.1% | The most aggressive expansive soil in the county at 55 to 71 percent clay over fractured Glen Rose limestone at 71 to 74 cm, cracking half an inch to 2 inches wide for 90 to 150 cumulative days most years, which means one slab can bear on solid rock at one corner and on clay swelling 16 percent at the other. |
| Ferris | — | LEP ≈ 17% | The highest linear extensibility recorded for any major component in the Comal and Hays survey area, 52.5 to 57.5 percent clay with densic bedrock at 89 cm, but it turns up in pockets on eroded Taylor and Navarro marl slopes southeast of the escarpment rather than across the county, so treat it as a lot-specific condition to check for and not a countywide one. |
Linear extensibility (LEP) is the USDA's measure of how much a soil changes volume between wet and dry. Higher numbers move houses.
Where we work in Comal County County
The Comal County County towns we cover.
Each one has its own page, because the ground changes inside this county and the local pattern is what matters when you are standing in the house.
What gets built here, and when
The oldest houses in Comal County are in New Braunfels
Comal County holds 201,628 residents and 84,882 housing units according to Census ACS 2024 one-year estimates, and the Census Bureau has named it among the nation's ten fastest-growing large counties. Under the houses, what that growth means is a county where most of the stock is recent slab-on-grade construction sitting on ground that was ranch or farm land a generation ago. New slab on old clay is the most common call we take here, and it usually shows up as a cracked brick line, a door that stopped latching, or a gap opening above a window on one side of the house only. The exception is the New Braunfels core, which carries the oldest stock in the county, where you find stone and masonry perimeter walls instead of a poured slab. Those houses get pier-and-beam repair and leveling, which is different work from slab piering and should be priced and scheduled as such. Out on the plateau side, pier-and-beam and crawl space construction shows up again on sloping lots where a level pad was never practical, and that is where crawl space repair and moisture control earns its keep. Unincorporated land across the county also carries manufactured homes, which need releveling on their own schedule as the piers under the frame work down into the soil. After any repair we come back once a year to check performance rather than leaving you to notice a problem yourself.
Permits in Comal County County
Who signs off on a foundation repair here.
Comal County itself does not issue residential building permits and does not enforce a residential building code on unincorporated land. What the county issues is on-site sewage facility permits, floodplain development permits, driveway permits in the county right of way, utility permits for aerial work, pavement cuts and non-pavement cuts, and Dark Skies outdoor lighting permits. The Fire Marshal permit applies to commercial buildings, public buildings and multifamily residential of four or more units, which by its own terms leaves single-family houses outside it. The county's permits page states plainly that its list is what Comal County requires, and that owners may still face requirements from property owners associations, municipalities and utility companies. So the practical answer depends on your address, not on the county. Inside New Braunfels, Bulverde, Garden Ridge, Selma or Schertz, the city sets the rules for a residential foundation repair, and we confirm with that city's building department before work starts rather than assuming. If a jurisdiction wants a letter from a professional engineer, that is a separate hire you make directly. Our inspectors are ICC certified. We are not engineers and we do not present ourselves as any.
Costs, warranty and inspections
The straight numbers in Comal County County.
Straight answers
Foundation questions people ask in Comal County County.
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