Subfloor Repair — Soft Spots, Water Damage and Squeaks
A floor that gives under your foot by the toilet, the patio door or the dishwasher — opened up, the rotted subfloor cut out and replaced, and the floor made solid before anything new goes over it.
Subfloor repair from JMB Builders: we open the floor at the soft spot, cut the damaged OSB or plywood back to the centers of the joists, check the joists, and let in new sheathing glued and screwed so the patch is flush with the floor around it. Squeaks get screws driven through the subfloor into the joists. Priced per project across the Twin Cities metro, quoted from your photos within one business day.
- Priced per project
- Cut back to solid wood, patched flush on the joists
- Joists checked and sistered if they need it
- Quote from photos in 1 business day
- Licensed MN contractor BC809005
A soft spot in the floor is the subfloor telling you it got wet. The usual places are in front of the toilet, under a leaking dishwasher or fridge line, inside a patio door where the sill leaked, and along an exterior wall under a window. OSB swells and crumbles when it stays wet; plywood delaminates. Either way the floor stops holding its shape, and any flooring laid over it will fail.
The repair is to cut the bad sheathing out to solid wood, on lines that land on the middle of a joist so the new piece has something to bear on, check the joists and the sill under it, and screw and glue a new piece in flush. If a joist is soft, we sister a new one alongside it. If the damage reaches the rim joist or a bearing wall, a structural engineer is brought in before we go further.
Squeaks are a different problem with an easier fix: the subfloor has pulled away from the joist and the nails are rubbing. Screws driven through the subfloor into the joists pull it back down. With carpet in place we can do it through the carpet with breakaway screws; with a hard floor we find the joists and screw at the edges or from below if there is a basement ceiling open.
What you supply
- Access: the room emptied, and the basement ceiling below if it is open
- The leak fixed, or tell us and we will bring in a plumber or look at the door or window that let the water in
- The new flooring you want over the repair, if we are doing that too
What JMB supplies
- Flooring and trim removal over the damaged area, and the toilet pulled if it is in the way
- Damaged subfloor cut out to the joist centers and hauled away
- Joist inspection, sistering where a joist is soft, and blocking at the patch edges
- New OSB or plywood to match the existing thickness, glued and screwed flush
- Squeak repair with screws through the subfloor into the joists
- A licensed plumber for a leaking supply, drain or flange when that is the cause
- Photos before and after for your job folder and, if it applies, your insurance claim
- The new flooring over the repair when you want it done in the same visit
How it is priced: per project
Quoted in writing from your photos within one business day. What moves the number:
- Size of the damaged area — one sheet's worth or a whole bathroom floor
- What has to come up to get to it: carpet, vinyl, tile or hardwood
- Whether the toilet, a vanity or a dishwasher has to come out and go back
- Joist damage that needs sistering, or a rim joist or sill that needs an engineer's look
- Whether the leak is fixed or a plumber has to find and fix it first
- Squeak repair alone vs. squeaks fixed while the floor is open for other work
- The new flooring going down over the repair
Send a photo of the soft area with something set on it for scale, one of what is around it (toilet, door, appliance), and one from below if the basement ceiling is open there.
How long it takes
A single soft spot: half a day to a day, plus the flooring over it. A whole bathroom subfloor with the toilet out: one to two days. Squeaks in a room: an hour or two.
How your project works
- 1
Send photos, get a written quote
Send three photos of the space and a sentence about what you want. You get a clear, itemized quote within one business day. We only come out to measure first when the job needs a tape measure — no pressure, no games.
- 2
Pick materials, or bring your own
We help you choose profiles and materials that fit the house and the budget, or match your existing millwork exactly — or you buy the door or trim yourself and we install it. Everything is confirmed before the crew is scheduled.
- 3
Clean, precise installation
The crew shows up on time, protects floors and furniture, and installs with tight joints and consistent reveals. Photos of the finished work go in your job folder.
- 4
Walkthrough and invoice
We walk the finished work with you. If anything is not right, we fix it before we call the job done. Then one invoice, paid by check or direct deposit — no card fees, no payment links.
Situations and options
Soft spot in front of the toilet
The most common one. Toilet pulled, floor cut out around the flange, flange checked, new subfloor let in, toilet reset on a new wax ring. A plumber replaces the flange if it is broken or rusted through.
Rot inside a patio or entry door
Water past the sill soaks the subfloor at the threshold. The door sill and the sheathing get cut back to dry wood, the rim joist is checked, and the door is re-flashed or replaced so it does not happen again.
Water damage under a kitchen appliance
A dishwasher, ice maker line or sink drain that leaked for months. The appliance and the cabinet toe kick come out, the subfloor is replaced, and the plumber fixes the source before the appliance goes back.
Squeaky floor
Screws through the subfloor into the joists, through the carpet with breakaway screws, at the edges of a hard floor, or from below through the basement ceiling. No demo, no patching.
Subfloor Repair — Soft Spots, Water Damage and Squeaks: questions, answered
What causes a soft spot in the floor?
Water, almost always. A toilet wax ring that failed, a dishwasher or fridge line that dripped, a patio door sill that leaked, or a window above that let water down the wall. OSB and plywood both lose their strength when they stay wet. Occasionally it is a joist that was cut for plumbing or a missing piece of blocking at a seam, which shows up as a floor that flexes but is not rotten.
Can you fix a squeaky floor without pulling up the flooring?
Usually. Through carpet we use screws with a scored head that snaps off below the surface. On a hard floor we screw at the edges under the base and shoe, or from below if the basement ceiling is unfinished. A squeak in the middle of a hardwood floor with a finished ceiling below is the hard case, and that one may need a few face-screwed and plugged holes.
Does the toilet have to come out to fix the subfloor under it?
Yes. The soft spot is usually right at the flange, and the flange is bolted to the subfloor we are replacing. We pull the toilet, cut the floor out around the flange, replace the sheathing, and reset the toilet on a new wax ring. If the flange itself is broken or rusted, a licensed plumber replaces it while the floor is open.
How do you know if the joists are damaged too?
Once the subfloor is off we can see and probe them. A joist that is dark and soft on top gets sistered with a new piece alongside it. A joist that is rotted through, or damage at the rim joist or a bearing wall, gets a structural engineer's look before we rebuild. We do not guess on that.
Will the patch be flush with the rest of the floor?
Yes. We match the thickness of the existing subfloor, land the edges on joists or add blocking so the new piece cannot sag, and glue and screw it. Any small difference gets feathered with floor patch. The finished floor going over it should not show a line, and a tile floor over a bad patch would crack, so we take that seriously.
Can subfloor repair be done in the same visit as the new flooring?
Yes, and it is the best way to do it. We repair the subfloor the first morning, let the glue and patch cure, and lay the new floor over it. If we find more damage than the photos showed, we tell you before we cut, with photos, and adjust the quote for what is actually there.
Get a written quote for this job
Three photos and a sentence is enough. You hear back within one business day. Or text the photos to 763-204-2099.
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Read morePage reviewed September 24, 2026 · JMB Builders LLC, MN license BC809005 · All flooring pages
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