I'm currently in the beginning stage of a bathroom remodel. All the flooring and subfloor has been removed, and I'm at the point where I am getting ready to replace some joists and sister one.
The first question I have is about the joist that I'm sistering to (video 0:50 to 2:00). I don't want to replace that joist because it is under a load bearing wall, and it is already up against several other 2x8s. It doesn't have much damage or deterioration, but there has definitely been water on it, and the top of it may be slightly rotted in a few places. Since I'm planning on leaving it in and just sistering a new joist on to it, is there something I should do to treat the existing joist to keep any mold/mildew/rot from spreading?
Second (related) question: For all the joists I'm replacing, and the one I'm sistering, I plan to use pressure treated 2x8s, since this is going in a bathroom. I just want to make sure that I never have to worry about water damage again, and one way to do that is to use pressure treated lumber for the joists as well as the sheathing/subfloor. Is there any reason I shouldn't use pressure treated lumber?
Any other tips or ideas for how I should go about this are appreciated.
Best Answer
In terms of sistering you don't need to treat the joist there if it has dried just sister the joists and attach the new subfloor to the new joists.
Pressure treated wood for joists and subfloor is going about this wrong. If those get wet from above things have already gone awry. If you end up with another leak in the future you'll still need to pull up everything to determine the extent of the damage.
If you are planning tile above the subfloor invest in a waterproofing system like schluter ditra as well as a good waterproofing system in the tub/shower area. Other systems are available as well.