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Full services directory How it worksFor prosAbout Get matched Call (866) 582-8523Six different failures produce the same dipping floor, and they cost wildly different amounts to correct. The expensive error is buying whichever fix the first company through the door happens to sell.
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.
Seeing something not on this list? Browse structural repair problems by symptom →
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 for: Relying 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.
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 for: A 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.
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 for: Free inspections that all conclude differently and all recommend the recommending company. That is not three opinions; it is three product catalogues.
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 for: A 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.
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 for: A 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.
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 →
Everyone else ranking for this is paid when you say yes. Here's when you shouldn't.
The problem archive — what the different patterns of movement actually indicate.
When the dip follows the line of the main carrying beam, or its posts have settled.
When the movement is local to one bay, or the joist ends have rotted at the bearing.
The most-quoted method, and the conditions under which it genuinely works.
When the movement is happening below the framing rather than within it.
The moisture conditions that cause and re-cause much of this damage.
What specifically is causing the sag, and what did you see that tells you so?
The answer should reference something they observed under your house, not a general explanation of settlement. Vagueness here means the remedy was chosen before the cause was.
What were the other possible causes, and how did you rule them out?
A good diagnostician can name the alternatives they considered. Someone who has never considered any is not diagnosing, they are matching your symptom to their product.
Is this movement still active, and what is your evidence?
The most consequential fact about a sagging floor, and the one most often asserted without support. Ask what would distinguish active from historic movement in your case.
How far do you plan to lift it, over what period?
Sets a realistic expectation and reveals experience. Anyone lifting a long-standing sag in one session will be having a conversation about your tile shortly afterwards.
What is in your scope about water and drainage?
If the answer is nothing and there is visible moisture, the repair is incomplete regardless of how well the carpentry is done.
What are you warranting, and against what outcome?
On sagging floors this is where "lifetime transferable warranty" needs unpacking: is the promise that the member does not fail, or that the floor does not move again? Those are entirely different commitments and only one of them is usually written down.
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