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Question DetailsAsked on 7/17/2017

What should I pay to replace 200 sq ft of old, rotten subflooring?

My bathroom/laundry room is about 200 sq ft of rotten flooring from water damage. I'm trying to figure up about how much it should cost to get the old flooring replaced with tongue and groove OSB boards.

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1 Answer


You say rotten flooring and then talking sub-flooring - if just the flooring (like wood over concrete) then typically about $1-2/SF for the removal, plus the cost of the new flooring.

If you mean the sheathing (OSB or particle board or plywood or such) part of the subflooring, commonly a few $/SF (say $3-5) to remove and replace - can be more like $5-10 if you need to replace the portion under walls as well, because that has to be propped up and supported during the sheathing replacement, which may have to be done from both sides of the wall if damage extends under the wall or if the bottom plate (the horizontal bottom 2x in the wall framing) is rotten too. Of course, for a bathroom, avoiding a seam near the walls by running the plywood in under the walls is better practice, and not very hard to do IF the bottom of the drywall on the bathroom side is being redone anyway.

If you mean the framing as well (floor joists) then depending on construction design, amount of utilities needing handling during the reframing, etc can easily run $20-30/SF for simple cases with normal wood framing (few if any utility runs in flooring, and floor joists simply supported at the ends on foundation or beams) to more like $30-70/SF if the framing needing replacement is continuous over beams or supporting load-bearing walls or such.

Here is another related question with answer FYI:

BTW - be sure to solve the water issue before putting in new subflooring - because if it is rotten you hae water coming from somewhere.

Also - why OSB T&G boards - in an environment like that where it may get wet, PLEASE do not use OSB or particle board or chip board, and the subflooring should be sheet, not T&G to reduce warping and bulging if it does get wet. And for the sheathing I would use treated plywood - more expensive by about $0.50/SF - with full sheet (seamless) vinyl or tile over it for water resistance. In laundry rooms I turn the flooring up at the walls to act as a retaining berm in case of flooding.

I like to also go with a couple inch waterproof raised sill at the entrance ot the laudnry area and waterproofed base of walls - preferably with a 3-4" dry floor drain to the outside to drain any leak or broken washer hose water. Such large drain pipe because only operating under an inch or so of head, so need larger pipe to handle the up to 10 gpm or so flow you many see. With laundry in bathroom, might be able to run a wet drain instead depending on how your DWV runs - but you want to be sure to connect to tub/shower, not toilet drain - and connecting it to trap in tub or shower does increase the possibility of a backup from the floor drain in event of a trap blockage. Going with a dry drain direct to the outside (legal because no sewage in it, and an emergency overflow only - so no different than a leak running under the wall to the outside.

Answered 3 years ago by LCD

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