Originally Posted by Della
Hi again Malcolm; I have been away and am about to get back in to it (rotten floor at rear bath). I do not need to replace the whole sheet of plywood, but saving the about 3' or so on the curb side seems like it might potentially weaken the curbside rear corner. Also, the "butt plate" spline support I would then need would be over the black water tank and would prefer not to take that out as it seems in tact. Any ideas or suggestions???
Richard (& Della)
This seems like an old thread but the information is still relevant to what you are wanting to do.
In general patching in a piece of new plywood to just replace the rotten part seems to be an OK approach and does not substantially weaken anything else if the new joints are either over frame members or there is some sort of spline at the joint. Do you have any space between the top of the black water tank and the bottom of the sub-floor to add a spline? If necessary I think you could use a thin spline. Maybe 1/4" plywood or perhaps even 1/8" metal strip. The key of course would be to not drill into the top of the black water tank. If there is absolutely no room you could route a groove in the edges of the new and old plywood pieces and slip in a wood or metal spline into the two grooves. It would be best to have a router to do that though. The basic idea here is to make sure that the new and old plywood are attached to each other. Feel free to PM me if you want to discuss more details.