subfloor in bath help

[seeflash]

While winterizing my 74' LY last week I noticed the subfloor under the sink and shower appears to be delaminating and close to rotted. Is there any way to repair it without removing the sink base and shower? Are there any other options? I will be replacing the sewer pipes/valves this weekend and droppping the rear belly pan so I will have access.

[Minno]

Depends on how much damage is there, and how extensive you want to get in repairing it. At a minimum, you’ll want to get all of the rotted and weak floor out, and that probably means some of it’s under the sink and shower.

Ideally, you’ll want to cut out a piece of floor that extends from a framing member to framing member so you can have good support for the patch. In other words, locate where the frame and cross pieces of the frame are by the elevator bolts, and use that as your guide for cutting the plywood out. Set you circular saw depth so it just cut through the plywood without damaging the frame. You’ll know if you hit the frame – sparks will fly and it’ll make a lot of noise. And dull your saw blade really fast… However, if you don’t remove the sink and shower, you’ll probably not be able to cut all the way to a framing member in all directions.

Cut the patch out of the same thickness plywood, and make it as tight to the hole as possible. That’ll give you the thinnest seam possible. For seams on the patch that fall on a framing member, you can use floor repair screws to screw the patch to the frame. These are available from Vintage Trailer Supply (http://www.vintagetrailersupply.com/Trailer_Floor_Repair_Screws_p/vts-387.htm) and other places I’m sure. For seams that do not fall on top of a frame, use a 4 to 6 inch wide piece of plywood as a spline underneath the entire length of the seam if you can. Glue and screw it to the underside of the plywood floor on both sides of the seam. Install the screws either from the top or the bottom. If you do out the screws in from the bottom, check the top of the floor to make sure none of them penetrate through to poke the bottom of a bare foot.

You most likely have a black water tank under the floor as well, so be extra careful! Last thing you want is to cut a slit in your tank with the saw, or puncture it with a screw.

Hope this helps.

Good luck,
Chris

[Lumatic]

You can use a penetrating epoxy wood treatment such as Rot Doctor. This won't fix the rotten areas but will seal the wood and prevent or at least minimize further rot.