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Our mobile home has very weak spots in the floor, right inside the door and under some windows. Do we cut out the weak particle board spots and replace it with plywood; tear out all the particle board and start over; or do we put the plywood over top the whole floor, weak spots and all? We want to finish it with linoleom on top if we can afford it, or a good layer of paint if we can't.

You can either do a patch job And replace it with either Plywood or OSB. DO NOT use particle board or MDF. You can replace all of the sub floor if you want, but if it is only a few areas I would cut & patch.

I do not recommend going over the top. The problem is that when the rest of the old subfloor falls apart you are left with nothing holding up the new floor.

Greg

If youre on a budget, you can cut out and replace what's damaged. Cut a little bit extra out beyond what's "soft" or water stained to be sure you get to something solid. Use the same thickness of material to patch it in. Be careful not to set your saw too deep when cutting, you might cut a wire or pipe underneath the floor. Id recommend adding some 2X4 blocking underneath your repair and use plenty of good quality screws for strength. Countersink the screws or get them flush to the floor so they wont pop up if you lay down vinyl.

Thanks for the information!

With my repairs, I always try to start and end the repair right down the center of a joist, so the new wood and existing wood has something to be nailed own to. When that is not possible, up against a wall for instance, then I have to frame in blocking to be that joist. The cuts going the other way will be spanning joists. There must be blocking under this cut. When fastening in the new wood, remember to re-nail/screw the edge of the existng subfloor to attach it to the joists and blocking as well. Nail pattern is 4"oc around the perimeter and 6"-8" in the field. I use PL adhesive with the screws to ensure no squeaks.

I would go with 3/4" plywood for the repair. 5/8" plywood is a nominal thickness. Actual thickness is 19/32". While this is closer to the thickness of 5/8" particle board, which actually is 5/8" thick, the 19/32" is a bit soft and spongy (I do believe 19/32" is legal with 16" oc joists though). Going to 3/4" (23/32" actual), you should end up with a lip on the edge of the repair because of the thicker plywood. This edge is reduced by floating out the difference with floor compound, to the point where the change is unnoticeable.

Hello,

We recently had this same problem. Our issue was there were leaks in the roof that were moving down the inside walls to the floors in some spots.

First, we had to find all of the bad floor spots, we then used a circular saw and cut out the bad particle board (this stuff sucks) and cleaned up the areas around the floor trusses.

We then cut 3/4" plywood to fit and used drywall screws to put them in place.

This has been a quick and easy fix and it holds up very good!

Hope this helps.

There must be blocking under the cuts between joists. If not, the plywood will be spongy and the existing particle board will break, unless it is a spot no one will ever step on.

When we redid the bathroom floor (after an undetected shower pan leak which resulted in the particleboard disintegrating,) we ripped out as much of the rotten particleboard, used a sawzall to get as close to the walls as possible. Then we sistered in 2 x 6 joists across the floor to the existing joists, even though the existing ones looked solid and dry. We figured that with all the work we had done so far, it couldn't hurt. After that we applied 5/8 inch marine grade plywood over the floor. There wasn't enough non rotten particle board to make any of it worth saving, so we did a total re-floor. I'd suggest once you identify all the soft spots in any particular room, stripping off the floor covering to see how much farther there is water damage, and then calculate out how much plywood you'll need.

BTW--sistering the joists added about $120 to the cost of the project, which we considered acceptable, given the amount of work we were already stuck with doing.

Mark's book shows exactly how to replace flooring.