The numbers · San Antonio–Austin corridor

Foundation repair statistics for San Antonio

Name: Foundation Risk by ZIP Code: San Antonio & Central Texas
Creator: Motmot Foundation Repair
Published: 2026-07-10
License: https://creativecommons.org/licenses/by/4.0/

These are the foundation repair statistics for San Antonio and Central Texas that we get asked for most, computed from our ZIP-level soil dataset. We scored 330 ZIP codes across 35 counties using USDA soil measurements. 89 of them (27%) rate High or Elevated for foundation-movement risk. Inside San Antonio the share is just over half: 31 of the city's 59 scored ZIPs. Every number on this page comes from that one dataset, and you can download the whole thing below, free.

330

ZIP codes scored

across 35 Central Texas counties

27%

rate High or Elevated

89 of 330 scored ZIPs

53%

of San Antonio ZIPs

31 of the city's 59 rate High or Elevated

highest ZIP score

78208, in San Antonio

spread in soil movement

shrink-swell runs 2.1% to 12.8% across the corridor

1 in 3

inspections end with no repair needed

a high score is not a diagnosis

Source: USDA NRCS SSURGO soil shrink-swell data, scored by Motmot. Three ZIPs have no score and are left out of the scored counts. Temple's 76508 is not a 2024 Census ZIP Code Tabulation Area, and downtown Austin's 78701 and the UT Austin campus ZIP 78712 are mostly urban land the USDA does not rate, so under half of each ZIP is rated. Scores were updated in October 2026, when we moved from sampling five points per ZIP to weighting every soil type by its actual area in the ZIP. Full methodology below. These figures describe the soil, not repair prices; for prices, see the cost guide.

How the corridor splits

A third of the corridor barely moves. A tenth of it moves a lot.

Of the 330 scored ZIPs, 111 (34%) land in the Lower band and 35 (11%) land in High. The biggest group is the middle: 130 ZIPs (39%) score Moderate. Central Texas ground runs from shallow soil over limestone that barely moves to deep expansive clay that moves a lot, and because each score weighs every soil in the ZIP by its area, a ZIP that holds some of both lands in between. ZIP-level shrink-swell spans 2.1% to 12.8% linear extensibility across the corridor, about a 6x spread. That is why two towns twenty minutes apart can have completely different foundation repair markets.

Risk-band split across the 330 scored ZIP codes. Bands: High = score 72-99, Elevated = 52-71, Moderate = 34-51, Lower = 5-33.

Dark expansive clay in a hand-dug pier hole beside a slab foundation edge — What a high score looks like in the ground: dark expansive clay beside a slab edge. This is the soil behind most of the corridor's foundation repairs.

Clay soil shrunk back from a slab edge below a brick wall during dry weather — The same clay in a dry spell, pulling away from a slab edge. Shrink in drought, swell in rain: that cycle is what the score measures.

San Antonio specifically

San Antonio scores worse than the corridor it anchors.

San Antonio has 59 scored ZIPs. 13 of them (22%) rate High, against 11% corridor-wide. The median San Antonio ZIP scores 52; the median corridor ZIP scores 41. Bexar County as a whole reads the same way: 36 of its 71 ZIPs (51%) rate High or Elevated. The city sits right where the Blackland-type clays meet the Balcones limestone, and at the ZIP level the clay side wins: only 2 of the 59 score in the Lower band.

Share of ZIP codes in each risk band: San Antonio's 59 scored ZIPs vs all 330. San Antonio is heavier at the top of the scale and lighter at the bottom.

The city's hottest ZIPs

78208 tops the city at 96, the highest score in the dataset. Twelve more San Antonio ZIPs rate High, from 86 down to 72, wrapping the central, south, east, and west sides:

782447820578202782377822578239782077821578219782427821878227

At the other end, only 2 San Antonio ZIPs score in the Lower band: 78266 at 33 and 78264 at 16, the lowest in the city. You can see every ZIP shaded on the interactive risk map, and every one of the 59 is ranked, with the soil under it, in our guide to which San Antonio ZIP codes have the most foundation problems.

County by county

Clay counties average more than twice the lowest counties.

Group the counties by their average ZIP score and the geology draws the map for you. The five highest averages (Guadalupe, Caldwell, Bexar, Bell, Williamson) all sit on or against the Blackland Prairie clays east of I-35; their 121 ZIPs average 54.8. The five lowest (Mason, Llano, Kinney, Frio, Wilson) average 23.2 across 23 ZIPs, most of them out west, away from the Blackland clays. Same climate, same builders, more than twice the soil movement.

Average ZIP risk score by county: the five highest and five lowest of the 35 counties in the dataset. County ZIP counts vary, so read these as area averages, not rankings of individual homes.

The top of the scale

Six ZIP codes score 85 or higher.

No ZIP reaches 99, the ceiling of the scale. The top six run from 96 down to 85, with soils measuring 11.3% to 12.8% linear extensibility over the top meter. Four are in Bexar County (three in San Antonio, one in Converse), one is Staples in Guadalupe County, and one is Rogers in Bell County. A meter of the soil under 78208 can change length by roughly 12.8% between saturated and dry, which is why slabs on it need drainage discipline or piers.

ZIP	CITY	COUNTY	SCORE	SOIL SHRINK-SWELL
78208	San Antonio	Bexar	96	12.8% linear extensibility
78670	Staples	Guadalupe	91	12.1% linear extensibility
78109	Converse	Bexar	88	11.7% linear extensibility
78244	San Antonio	Bexar	86	11.4% linear extensibility
76569	Rogers	Bell	85	11.3% linear extensibility
78205	San Antonio	Bexar	85	11.3% linear extensibility

Stair-step crack in brick veneer below a window on a Central Texas home — What the high end of the scale does to houses: stair-step brick cracking after the clay shifts a slab edge. The most common sign we inspect.

Motmot inspector recording floor elevation readings on a tablet during a free inspection — The score says what the soil can do. A floor-elevation survey says what your house has actually done. The survey is free.

One caution before you read your own ZIP off the table. The score describes soil potential, not damage. We write no repair on about a third of the houses we measure, and that holds in high-scoring ZIPs too. If your ZIP runs hot, the right response is a free measured inspection and good drainage habits, not panic.

Methodology

Where the numbers come from.

Every statistic on this page is computed from one dataset: the ZIP-level soil scores behind our Central Texas foundation risk map. The soil measurements are USDA NRCS SSURGO data, the national soil survey, accessed through the USDA's public Web Soil Survey. For each ZIP we take linear extensibility, the USDA's measure of how much a soil shrinks and swells with moisture, over the top 100 cm, weighted by soil component and depth, for every USDA soil map unit inside the ZIP, and we weight each map unit by its area in the ZIP. A ZIP is scored only when at least half its area is rated by the USDA soil survey, so downtown cores that are mostly unrated urban land show no score. That value is rescaled to a 5 to 99 score and grouped into four bands. The scores, bands, and driver labels are Motmot's interpretation of the USDA measurements. They are not a USDA product, and they describe soil potential by area, never the condition of a specific house. For the plain-English science, see our Texas clay soil guide. For how the same clay behaves across the rest of the state, see foundation problems in Texas.

The dataset

Download the data. Use it with credit.

The full dataset is a plain CSV: 333 ZIP codes, one row each, about 30 KB. No signup, no email gate. The USDA's underlying measurements are public domain; Motmot's compilation and scoring are licensed CC BY 4.0, so journalists, researchers, realtors, and anyone else can use it, publish from it, or build on it, commercially included, with credit to Motmot Foundation Repair and a link.

Download the CSV (333 ZIPs)Data dictionary & license (README)

COPY-READY CREDIT LINE

Data: Motmot Foundation Repair, motmotfoundationrepair.com · foundation risk by ZIP, from USDA NRCS SSURGO soil data (CC BY 4.0)

CITATION FORMAT

Motmot Foundation Repair (2026). Foundation Risk by ZIP Code: San Antonio & Central Texas. Derived from USDA NRCS SSURGO soil survey data. https://motmotfoundationrepair.com/foundation-repair-statistics-san-antonio/

CREDIT LINE WITH A LINK (HTML)

<a href="https://motmotfoundationrepair.com/foundation-repair-statistics-san-antonio/">Foundation risk by ZIP code</a> by <a href="https://motmotfoundationrepair.com/">Motmot Foundation Repair</a>, from USDA NRCS SSURGO soil data, licensed <a href="https://creativecommons.org/licenses/by/4.0/">CC BY 4.0</a>

Paste whichever of the three fits where you are publishing. CC BY 4.0 means you can use it, share it, and build on it, including commercially, as long as you credit Motmot Foundation Repair with a link to motmotfoundationrepair.com. The underlying USDA measurements are public domain.

What each column means

zip	5-digit ZIP Code Tabulation Area
city	Primary USPS city for the ZIP
county	Texas county
risk_score_0_99	Motmot's foundation-movement risk score (soil shrink-swell rescaled to 5-99; empty where the ZIP has no score)
risk_band	High (72-99), Elevated (52-71), Moderate (34-51), Lower (5-33), or No data
linear_extensibility_pct	USDA soil linear extensibility percent, weighted mean over the top 100 cm
primary_soil_driver	Plain-language driver: expansive clay, seasonal clay movement, or thin soils over limestone
latitude, longitude	ZIP centroid

Version 2026-07-10. The interactive map application itself stays under its own CC BY-NC-ND 4.0 license; the open CC BY 4.0 license above covers this dataset. If you publish something with it, we'd genuinely like to see it: get@motmotfoundationrepair.com.

Foundation statistics FAQ

Questions people ask about these numbers

Which San Antonio ZIP codes have the highest foundation risk?

78208 tops the city at 96, the highest score in the dataset. Twelve more San Antonio ZIPs rate High, from 86 down to 72: 78244, 78205, 78202, 78237, 78225, 78239, 78207, 78215, 78219, 78242, 78218, and 78227. The pattern follows the soil: deep expansive clay runs through the central, south, east, and west sides, while much of the far north side sits on shallow limestone and scores lower.

Does a high risk score mean my foundation will fail?

No. The score measures the soil, not your house. A high score means the clay under that ZIP can shrink and swell enough to move a slab, and whether it actually does depends on drainage, plumbing, trees, watering habits, and how the house was built. Plenty of homes on high-score clay stay flat for decades. Roughly one inspection in three ends with no repair needed, and that includes plenty of homes in high-scoring ZIPs. Treat the score as a reason to pay attention, not a verdict.

Where does this data come from?

The soil measurements come from the USDA NRCS SSURGO database, the national soil survey. For each ZIP we take the linear extensibility of every soil map unit inside the ZIP over the top 100 centimeters, weighted by soil component and depth, and weight each map unit by its area in the ZIP. That number is rescaled to the 5 to 99 score. The scoring and the risk bands are Motmot's interpretation of the USDA measurements, not a USDA product.

Can I use or republish this dataset?

Yes. The CSV is licensed CC BY 4.0: use it, share it, and build on it, including commercially, as long as you credit Motmot Foundation Repair with a link to motmotfoundationrepair.com. The underlying USDA measurements are public domain. Note the interactive risk map application is licensed separately (CC BY-NC-ND 4.0); the open license covers the dataset.

Is the north side or the south side of San Antonio worse for foundations?

The south and east sides sit on deep expansive clay and carry most of the city's high scores. Much of the far north side sits on shallow limestone and scores near the bottom of the Moderate band, 34 in 78255, 78256, and 78261. The sharpest movement we measure is often in between, on transition streets where one corner of a house rests on rock and another on a clay pocket. The dataset gives you the ZIP-level reading; an elevation survey tells you what your specific lot is doing.

How many ZIP codes does the dataset cover?

333 ZIP codes across 35 Central Texas counties, from San Antonio through San Marcos and Austin up to the Temple area. 330 of them carry a score. Three have no score and are marked accordingly. Temple's 76508 is not a 2024 Census ZIP Code Tabulation Area, and in downtown Austin's 78701 and the UT Austin campus ZIP 78712 under half the ground is rated, because most of it is urban land the USDA does not rate. Every row lists the ZIP, city, county, risk score, risk band, soil linear extensibility, primary soil driver, and the ZIP's centroid coordinates.

Your ZIP sets the odds. Your house is a measurement.

A free Motmot inspection turns the statistics into a straight answer for your address: a floor-elevation survey, crack mapping, and a read, including 'no repair needed' when that's the truth.

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