After moving some walls for a remodel and re-wiring much of my house, there are several 3/4″ holes in the plywood subfloor where wires used to pass through.
I’m planning to install 3/4″ white oak floors — do I need to fill these holes first, or just lay the paper and hardwood over them? If they need to be filled (for fireproofing?), what should I use?
Also, what is the correct type of caulk to seal the floor penetration holes for wiring inside the new walls? The old ones seem to be filled with clear silicone caulk.
Thanks!
Replies
You don't need to fill the holes in the subfloor.
You don't need to fill the holes for the wiring either. We do this where we want to minimize air exfiltration to an unheated space but no where else. We use expanding foam. If you do it all at once, one can will do all the holes.
I wouldn't do anything at all about the old holes.
But to pass inspection here, you'd have to fire-stop all the new holes that travel through the plates in your stud bays. Here we use fire-stop caulking. Buncha different brands out there.
Thanks. I just called the inspector and he said the same thing. I do need to fire-stop the new wiring penetrations. Filling the other holes would be a good idea but is not required. He said most builders use expanding foam.
Firestop the holes that go from one assembly to another using firestop caulk - about $12 a tube. When I say "assembly" I mean a floor system, wall system, ceiling assembly. So, a hole that is drilled in bottom plate of a wall would connect the floor system to the walls and allow fire to move more quickly from underneath the floor to the interior of the wall cavity. A hole that is drilled in the wall top plates connects the wall cavity to the ceiling assembly. For larger holes the best thing is to block with 3/4" wood - or use rockwool - although rockwool is hard to find, and it is not accepted by some inspections departments.
Regarding the holes in the floor, filling them is not required, but it's just good building practice. Personally I use bondo or Durham Rock Hard putty. If you can get underneath to add some wood with some short nails and glue that is the best thing, but it is not completely necessary, it just help the filler stay in the hole while it's drying. I guess foam would be fine too, but it is just such a mess to work with...