How do I tell what foundation my house has?

Look. A basement has stairs going down. A crawl space has a hatch or a vent near ground level, with joists visible underneath. A slab has neither: the floor meets the ground and plumbing comes up through the concrete. Five minutes gives certainty no dataset can.

What does the Census foundation data tell me?

It gives the share of new single-family houses completed in a region and year on each foundation type, from the Census Survey of Construction. It describes a population of houses, not yours. Treat “most likely” as a hypothesis to confirm.

Why does the tool say my answer is weak?

Because no single type had a clear majority in that region and period. US houses in 1971 were 36% basement, 38% slab and 26% crawl space, a near three-way split. Saying so is more useful than naming a winner by two points.

Why has slab construction grown so much?

We show the shift but do not assert a cause we have not sourced. The Census series records that the US slab share roughly doubled from 1971 to 2025 while basements and crawl spaces more than halved, with big regional differences.

Can a house have more than one foundation type?

Yes, often. Additions frequently sit on a different foundation from the original house, and the joint between two systems that move differently is where problems show first. This tool cannot see that, which is another reason to look.

Does foundation type tell me what repair I need?

No. The repair method follows the movement that was measured, not the foundation type. The repair method selector starts from movement, and the repair methods guide compares the options.

Is a crawl space worse than a slab?

No, just different. Crawl spaces have moisture and ventilation issues slabs do not; slabs make plumbing leaks harder to find and reach. See foundation types and the crawl moisture check .

How current is this foundation data?

The Census “type of foundation” series runs from 1971 to 2025 and was retrieved on 2026-09-05. Census rounds each percentage separately, so the three may not total exactly 100.

HyreFoundation tools

What foundation does my house have?

Five minutes with a flashlight answers this for certain. When you cannot look, Census data on what was built shows the odds.

75% slab new US homes, 2025 (38% in 1971) Census Survey of Construction, foundation type of new single-family houses completed. Basements fell from 36% to 16%. Retrieved 2026-09-05.

This tool shows which foundation type was most common for new houses in your region and build year, using the Census Survey of Construction, and how confident that answer is.

Region matters more than year: 2025 homes were 53% basement in the Northeast and 4% in the South. It describes what was built, not what is under your house.

What was built there, then

Census distribution, not a statement about your house. Nothing is emailed.

— Most likely

— How confident

— Full distribution

— How to confirm in five minutes

— How the region has changed

— Note

What this assumed —

What was built, not what survives. A regional distribution, never a statement about your house.

Foundation type is the one question you can answer yourself for free

Five minutes and a flashlight settle it with certainty. The data below is for when you cannot get to the house — a listing, an inherited property, a purchase from out of state.

A basement has stairs going down. A crawl space has a hatch or a vent at ground level and you can see joists underneath. A slab has neither: the floor meets the ground, there is nothing below it, and the plumbing comes up through the concrete. No dataset beats looking.

What the country builds has changed enormously. In 1971, new US single-family houses were 36% basement, 38% slab and 26% crawl space — close to a three-way split. In 2025 they were 16% basement, 75% slab and 9% crawl. The slab share roughly doubled while basements and crawl spaces both fell by more than half.

The regional differences are larger than the national trend. New houses completed in 2025 were 53% basement in the Northeast and 50% in the Midwest, against 4% in the South, where 88% were slab. Region tells you far more than year does.

The crawl space is the type that quietly disappeared. In the South it fell from 38% of new houses in 1971 to 8% in 2025.

If you own a Southern crawl space, you own something that was common when it was built and is rarely built now — which affects who is familiar with it and what they propose.

What this data is not. It records what was built in a given year, not what survives today, and it is a regional distribution rather than a statement about any one house. Additions and rebuilds routinely give a single house more than one foundation type, and the tool has no way to know that.

New houses completed in 2025, by region

Census percent distribution. Components may not total 100 — each is rounded independently.

Region	Basement	Slab or other	Crawl space
Northeast	53%	40%	7%
Midwest	50%	43%	7%
South	4%	88%	8%
West	16%	70%	14%
United States	16%	75%	9%

Identifying it in five minutes

In order. Stop at the first one that matches.

Are there stairs going down from inside the house?
Then it is a basement, full or partial. Partial basements are common in older housing and often sit alongside a crawl space under a later addition — check whether the whole footprint is served.
Is there a hatch, door or vent at ground level around the perimeter?
Then it is a crawl space. Look for framed openings low on the exterior wall, or an access hatch inside a cupboard or under the stairs.
Does the floor meet the ground with nothing underneath?
Then it is a slab. The clearest confirmation is the plumbing: on a slab, supply and waste come up through the concrete rather than being visible from below.
Does the answer change from one part of the house to another?
Very common, and important. An addition frequently sits on a different foundation from the original house, and the joint between them is where differential movement shows up first.
Still unsure after all four?
That is itself a finding worth noting. A house whose foundation type is not obvious from inside usually has an access problem, and access is what an inspection depends on.

Questions this calculator answers

How do I tell what foundation my house has?: Look. A basement has stairs going down. A crawl space has a hatch or a vent near ground level, with joists visible underneath. A slab has neither: the floor meets the ground and plumbing comes up through the concrete. Five minutes gives certainty no dataset can.
What does the Census foundation data tell me?: It gives the share of new single-family houses completed in a region and year on each foundation type, from the Census Survey of Construction. It describes a population of houses, not yours. Treat “most likely” as a hypothesis to confirm.
Why does the tool say my answer is weak?: Because no single type had a clear majority in that region and period. US houses in 1971 were 36% basement, 38% slab and 26% crawl space, a near three-way split. Saying so is more useful than naming a winner by two points.
Why has slab construction grown so much?: We show the shift but do not assert a cause we have not sourced. The Census series records that the US slab share roughly doubled from 1971 to 2025 while basements and crawl spaces more than halved, with big regional differences.
Can a house have more than one foundation type?: Yes, often. Additions frequently sit on a different foundation from the original house, and the joint between two systems that move differently is where problems show first. This tool cannot see that, which is another reason to look.
Does foundation type tell me what repair I need?: No. The repair method follows the movement that was measured, not the foundation type. The repair method selector starts from movement, and the repair methods guide compares the options.
Is a crawl space worse than a slab?: No, just different. Crawl spaces have moisture and ventilation issues slabs do not; slabs make plumbing leaks harder to find and reach. See foundation types and the crawl moisture check.
How current is this foundation data?: The Census “type of foundation” series runs from 1971 to 2025 and was retrieved on 2026-09-05. Census rounds each percentage separately, so the three may not total exactly 100.

Sources and methodology

Figures dated 5 September 2026. Last reviewed August 16, 2026.

Survey of Construction — Characteristics of New Housing, type of foundation (U.S. Census Bureau, retrieved 2026-09-05. Source for every percentage on this page: foundation type of new single-family houses completed, by region, 1971 to 2025. Components may not total 100 because Census rounds each independently.)

Foundation types: slab, crawl space and basement How each type is built and how it tends to fail.
Why foundations move Soil, water and load, whatever the foundation type.
Crawl space repair Moisture and support problems specific to crawl spaces.
Repair method selector Method follows movement, not foundation type.

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