A toilet in an unused bathroom sprung a leak that went unnoticed until carpet outside the door got wet. I've taken up the old tile, linoleum and plywood. Under the plywood are diagonal boards (sub-subfloor?) over the crawl space. After drying the room for a month I filled the termite-eaten boards around the toilet with Bondo, and now I'm ready to lay down new 3/4" ACX plywood. I'm new at this and I'm hoping someone will be generous enough to answer a few questions.
The previous plywood had large gaps between it and the walls. Any reason for this? I cut the new plywood for a tight fit.
There are gaps between the ends of diagonal boards that come together on a floor joist. The gaps were filled with what looks like portland cement (?). Wondering why filling 1/2" over a beam was important when some of the boards are spaced wider than that. Much of the cement crumbled out when removing the plywood. Should it be replaced?
The space between the old plywood and the walls was filled with the same cement. I asked someone at the local lumber yard about this but he didn't know what I was talking about - said I should just use some kind of waterproof caulking around the edges. Good advice?
Any reason for NOT using construction screws instead of nails to hold down the plywood?
Thanks, Dave