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 331 ZIP codes across 35 counties using USDA soil measurements. 104 of them (31%) rate High or Elevated for foundation-movement risk. Inside San Antonio the share is half: 30 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.

331

ZIP codes scored

across 35 Central Texas counties

31%

rate High or Elevated

104 of 331 scored ZIPs

51%

of San Antonio ZIPs

30 of the city's 59 rate High or Elevated

ZIPs max the score at 99

two of them in San Antonio

34x

spread in soil movement

shrink-swell runs 0.5% to 17% 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. Two downtown-Austin ZIPs have no residential soil data and are excluded from the scored counts. Full methodology below. These figures describe the soil, not repair prices; for prices, see the cost guide.

How the corridor splits

Half the corridor barely moves. A fifth of it moves a lot.

Of the 331 scored ZIPs, 152 (46%) land in the Lower band and 70 (21%) land in High. The middle is thinner than people expect. Only 15 ZIPs score between 60 and 89, because Central Texas ground tends to be one thing or the other: shallow soil over limestone that barely moves, or deep expansive clay that moves a lot. Soil shrink-swell spans 0.5% to 17% linear extensibility across the corridor, a 34x spread. That is why two towns twenty minutes apart can have completely different foundation repair markets.

Risk-band split across the 331 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. 23 of them (39%) rate High, against 21% corridor-wide. The median San Antonio ZIP scores 56; the median corridor ZIP scores 35. Bexar County as a whole reads the same way: 35 of its 71 ZIPs (49%) rate High or Elevated. The city sits right where the Blackland-type clays meet the Balcones limestone, so it gets both extremes, and the clay side is the bigger half.

Share of ZIP codes in each risk band: San Antonio's 59 scored ZIPs vs all 331. San Antonio is heavier at the top of the scale and lighter at the bottom.

The city's hottest ZIPs

78216 and 78208 max the score at 99. Fifteen more San Antonio ZIPs sit at 90, wrapping the central, south, east, and west sides:

782017820578210782187821978220782227822578226782277822878237782397824478245

At the other end, 16 San Antonio ZIPs score in the Lower band, most of them along the limestone north side. The lowest in the city is 78203 at 7. You can see every ZIP shaded on the interactive risk map.

County by county

Clay counties average three times the limestone counties.

Group the counties by their average ZIP score and the geology draws the map for you. The five highest averages (Guadalupe, Caldwell, Bell, Bexar, Williamson) all sit on or against the Blackland Prairie clays east of I-35; their 122 ZIPs average 56.7. The five lowest (Lampasas, Llano, Burnet, Mason, Wilson) average 18.0 across 26 ZIPs, most of them on the shallow limestone and granite country west of the corridor. Same climate, same builders, three times 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

Ten ZIP codes max out the score.

Ten ZIPs hit 99, the ceiling of the scale, all with soils measuring 17% linear extensibility over the top meter. Five are in east and north-central Austin, two are in San Antonio, and three are smaller Blackland towns. A meter of this soil can change length by roughly 17% between saturated and dry, which is why slabs on it need engineering, drainage discipline, or piers.

ZIP	CITY	COUNTY	SCORE	SOIL SHRINK-SWELL
78208	San Antonio	Bexar	99	17% linear extensibility
78216	San Antonio	Bexar	99	17% linear extensibility
78702	Austin	Travis	99	17% linear extensibility
78721	Austin	Travis	99	17% linear extensibility
78722	Austin	Travis	99	17% linear extensibility
78723	Austin	Travis	99	17% linear extensibility
78757	Austin	Travis	99	17% linear extensibility
76501	Temple	Bell	99	17% linear extensibility
78140	Nixon	Gonzales	99	17% linear extensibility
78614	Cost	Gonzales	99	17% 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. About a third of our inspections end with no repair needed, 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 of the dominant soils, weighted by soil component and depth, averaged across sample points in the ZIP. That value is rescaled to a 5–99 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 no soil data exists)
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 used for soil sampling

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?

78216 and 78208 top the city at 99, the maximum score in the dataset. Fifteen more San Antonio ZIPs score 90: 78201, 78205, 78210, 78218, 78219, 78220, 78222, 78225, 78226, 78227, 78228, 78237, 78239, 78244, and 78245. 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 far 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 99-score clay stay flat for decades. About a third of our inspections end 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 the dominant soils over the top 100 centimeters, weighted by soil component and depth, and average it across sample points. That number is rescaled to the 5–99 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 in the Lower band. 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. 331 of them carry a score; two downtown-Austin ZIPs (78701 and 78712) have no residential soil survey data and are marked accordingly. Every row lists the ZIP, city, county, risk score, risk band, soil linear extensibility, primary soil driver, and the coordinates used for sampling.

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 an honest read, including 'no repair needed' when that's the truth.

Now booking free inspections in Central Texas.

Schedule a Free Inspection (210) 816-0034