Sagging floor repair - diagnose before you buy a cure

What is sagging floor repair?

A sagging floor is a symptom, not a diagnosis. Underneath it sits one of a handful of quite different failures: settlement in the foundation, a failed or overloaded carrying beam, a post whose footing has sunk, joists rotted at their ends, joists that were undersized for their span from the day the house was built, or persistent crawl-space moisture doing slow damage to all of the above. Each has a different remedy and a different price, and the single most expensive mistake here is buying a fix before anyone has established which one you have.

Signs you need sagging floor repair

• A floor that dips toward the middle of the house, usually along a line rather than in a patch - that line often marks the main carrying beam
• A marble, a ball or a dropped pen that consistently rolls the same direction across a room
• Doors that swing open or closed on their own, or that have started binding at one corner of the frame
• Gaps opening between baseboard and floor, or a visible taper where a hardwood run meets a wall
• Bounce or vibration when someone walks past, or china that rattles in a cabinet as people cross the room
• A high spot or hump rather than a dip - which points at something quite different from settlement
• Sloping that is noticeably worse in one room, or that stops abruptly at a wall line
• Sagging that has visibly changed in the last year, as opposed to a slope the house has always had

Seeing something not on this list? Browse structural repair problems by symptom →

How sagging floor repair actually works

1. 1

   Measure it, and date the measurement

   Before anyone is called, record what is actually happening. Take levels at a grid of points across the affected rooms and write them down with the date. Photograph the underside of the floor from the basement or crawl space with something in frame for scale. This costs nothing and it is the only way to answer the question every professional will ask: is this still moving, or did it finish moving decades ago?

   Watch forRelying on memory. "It seems worse" is not evidence, and without a baseline nobody can distinguish a live problem from an old one - which is the difference between a repair and no repair at all.

2. 2

   Work down the causes, from the framing to the ground

   A dip following the beam line points at the beam or the posts under it. A dip local to one bay points at individual joists. Sag worst near an exterior wall, with soft dark wood at the bearing, points at joist-end rot and therefore at water. Sag across a whole side of the house, with cracking upstairs and outside, points below the framing at the foundation. A springy floor that is level points at span rather than damage. And a hump rather than a dip sometimes means something has been jacked before.

   Watch forA contractor who arrives already knowing the answer. Everyone in this trade sells a specific remedy, and the diagnosis that arrives before the inspection is usually the one that matches the truck.

3. 3

   Get an independent determination before choosing a remedy

   This is the decision point where money is made or lost. The remedies here range from a modest carpentry job to work costing many multiples of it, and they are not interchangeable. A licensed structural engineer, paid for time rather than for a repair, will say which failure you have and specify the fix - a document you can then put in front of three bidders. The full argument for why that works is on the engineering referral path.

   Watch forFree inspections that all conclude differently and all recommend the recommending company. That is not three opinions; it is three product catalogues.

4. 4

   Fix the cause, not only the level

   Where rot or moisture is involved, the carpentry is half the job. Ground moisture in a crawl space, drainage delivering water to the foundation, a leak overhead - if these are still running when the new wood goes in, the clock simply restarts. Where the cause is below the framing, correcting the floor without correcting the ground is a temporary result you will pay for again.

   Watch forA quote that levels the floor and says nothing about water. Ask what is being done about the source and get it named in the scope.

5. 5

   Lift slowly, and stop before perfect

   Recovery is done gradually - over days and weeks, in small increments - because everything above the floor has spent years settling into the sagged shape. Drywall, tile, door frames, cabinets and plumbing connections all have to come back with it, and rushed lifting cracks them. Full recovery is frequently neither achievable nor desirable: some deflection is permanent set, and chasing the last of it does more damage than it repairs.

   Watch forA promise of a perfectly level floor, or a schedule that lifts everything in a single visit. Both are signs that the person quoting has not done many of these.

What does sagging floor repair cost?

The range here is the whole point: correcting a settled post footing and underpinning a foundation both cure a sagging floor and are not remotely the same expense. Until the cause is established, any single number you are quoted is a guess about which problem you have.

See the full sagging floor repair cost guide - by material, size and region →

If the number is the problem, here are the ways people pay for it →