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Sagging and sloping floors: what's underneath
Over a crawl space, a soft or sagging floor is usually the framing or the interior piers: rotted or undersized joists, a beam that has dropped, piers that have sunk into soft soil. On a slab, a floor that slopes toward one side is the slab itself moving with the soil. The first tells you to look under the house; the second tells you to look at the soil.
When it is serious
- A slope that runs across the whole house, not one room
- Cracks in tile or a slab that line up with the low spot
- Gaps under baseboards on the low side
- Doors on the low side that swing open on their own
When it is usually cosmetic
- A local dip over a crawl space from a single bad joist
- A bounce in an older floor with no slope
What the soil under your address does to this answer
Pier-and-beam houses on expansive clay move more, not less, than slabs: the interior piers sit on the same soil and each one moves on its own. That is why 'pier and beam foundation repair' is its own search in Houston and Dallas. Slab houses on very high shrink-swell soil slope when one edge dries out faster than the other, typically the sunny or tree side.
Pier and beam vs. slab: which house you have
A pier and beam foundation holds the house on wood or concrete piers over a crawl space; the floor is framed on beams and joists, and there is air under it. A slab foundation is a concrete plate poured on the ground; the floor is the slab. Older houses in Texas and the South are often pier and beam; most houses built since the 1970s are slabs.
The difference decides who to call. On pier and beam, a sagging floor is usually a framing or interior-pier job that a carpenter or foundation contractor can price by the item. On a slab, a sloping floor is the foundation itself, and the repair is priced by pier count after an engineer's elevation survey.
Check the soil under an address
USDA soil survey, read for the top 60 inches under the address. Free, no account, nothing is sent to a contractor.
Usually 1–3 seconds. The USDA service occasionally takes longer.
What the repair costs, if it is one
| Repair | Published range | When it's the right tool | Source |
|---|---|---|---|
| Mudjacking / slabjacking | $500–$1,300 per job | A sunken slab section (patio, garage, walkway) on stable soil. Lifts; does not stop shrink-swell. | Bob Vila — How Much Does Foundation Repair Cost?, updated 2024-05-29 |
| Piering / underpinning | $1,000–$3,000 per pier | Settlement or heave on expansive or weak soil. The pier COUNT is where quotes diverge most; an engineer's report specifies it. | This Old House — Foundation Repair Cost, updated 2026-03-06 |
| Drainage system | $2,800–$6,500 per job | Often the first, cheapest fix on wet or moderately expansive soil. | Bob Vila — How Much Does Foundation Repair Cost?, updated 2024-05-29 |
| Settling / sinking repair (all methods) | $4,500–$20,000 per job | The typical range a pier job lands in; the top end is a whole-house pier plan. | Bob Vila — How Much Does Foundation Repair Cost?, updated 2024-05-29 |
What to do next
For a crawl space, look first: moisture, rot, dropped beams. For a slab, an elevation survey. Then check the soil.
Questions people ask
How much does it cost to fix a sagging floor?
A single joist or sistered beam is a carpentry job, not a foundation repair, and we cite no range for it. Interior piers are priced per pier (table below); a slab that has moved is a foundation repair priced by pier count.
Is a sloping floor a sign of foundation problems?
On a slab, usually yes if it runs across the house. Over a crawl space, often not; check the framing before the foundation.
We are not engineers and this is not an engineering opinion. We report public soil-survey data and published price ranges. Nothing here states that a specific house is or is not structurally sound; a licensed structural engineer who has seen the house can.