BasementSoil

What the soil under your house says about your basement

Enter a ZIP code. We show you the USDA soil survey classification for that county — how long the ground stays saturated, how much it swells and shrinks, and how close the water table comes to basement depth. Public federal data, stated plainly, with no contractor deciding what you get to see.

Every county in the 50 states and DC — 3,142 of them. Where basements are common the report is about the basement. Where houses sit on slabs — Texas, California, Florida and most of the South — the same soil data is about the slab and the footings instead, because that is the problem those counties actually have.

Three numbers, three completely different repairs

Water damage and movement damage get sold as one product. They are not one problem. The soil survey separates them, and the separation is worth thousands of dollars.

The ten tools, in the order you would actually use them

  1. Soil lookup — drainage class, shrink-swell and water table for a ZIP code.
  2. Is it condensation, seepage or structural? — a decision tree, not a quiz.
  3. Crack rater — width, direction and progression decide whether it is ugly or serious.
  4. Crack tracker — log measurements over months and see the trend.
  5. Repair cost calculator — by dimensions, problem and solution.
  6. Interior vs exterior comparison — price, invasiveness, lifespan.
  7. Sump pump sizing — the calculation most quotes skip.
  8. Downspout and drainage calculator — how much water your roof puts next to your wall.
  9. Contractor visit checklist — printable, and it makes the salesman uncomfortable in a useful way.
  10. Radon expectation — the adjacent problem that shares the same sub-slab route.

Highest combined risk in our coverage

Why these counties — the geology behind the ranking

Worst soil for foundation cracks specifically

Different list, and that is the point. These counties are often dry. The ground still moves.

Expansive clay and why one house cracks and the neighbour does not

Where the data comes from

Soil values are from the USDA NRCS Soil Survey Geographic Database (SSURGO), the national soil survey, queried through the free Soil Data Access service. It is public data produced by soil scientists over decades of field mapping. We aggregate it to county level and translate the vocabulary; we do not adjust the values.

Repair costs are different in kind, and we label them differently everywhere they appear. There is no free machine-readable dataset of US basement waterproofing prices. Our figures are a model built from published editorial ranges and a regional labour factor. Anyone showing you a precise “average price in your ZIP” without saying that is guessing at you.

Full methodology, field by field · How this site is funded

Fair questions

Is this free?

Yes, and there is nothing to sign up for. If you ask us to pass your details to contractors we may be paid a referral fee — that is disclosed at every point where we ask, and it is the only way the site earns anything.

Do you sell my information?

Only if you tick the consent box and submit the quote form, and then only to the partners named on this page. Browsing the site sends nothing to anyone. You can opt out at any time and we process removals within 10 business days.

Why does the Texas or Florida page not talk about basements?

Because almost nothing there has one. Building practice across the South and much of the West is slab-on-grade, driven by climate, frost depth and soil. A basement moisture score for those counties would be a number with no use — so those pages use the same USDA data to describe what the ground does to a slab and its footings. Shrink-swell clay in Dallas, Houston or the California Central Valley causes more foundation damage in dollar terms than groundwater does in the whole basement belt.

How current is the soil data?

SSURGO changes slowly. Soil survey areas are re-certified over years, not weeks, so a yearly refresh is enough and we state the fetch date on every county page. That is deliberate: the data does not need constant attention, which means the effort goes into explaining it.

Page data updated