Is it normal for a shower subfloor to consist of slats, roofing felt, cement board, and tile, or should I replace it with plywood?
So, we had a bit of a situation with our shower – there was a leak that we didn’t catch right away because there was a little puddle forming on the floor. After tearing out some drywall and tile to get to the subfloor, we discovered that there wasn’t actually a subfloor there – just some slats, roofing felt, cement board, thin set, and tile. I was expecting to find plywood in there, so I’m not sure what to do next. Should I just replace it with roofing felt and cement board, or do I need to go all out and rip out the whole bathroom to lay down plywood subflooring? I’ve never come across this before, so I’m feeling a bit lost. Check out the photos – the first one shows what was under the roofing felt, and the second one shows the roofing felt and backer board. Any advice would be appreciated! 
My house was built in 1955 and has the same sub floor.
Good to know that this was a common practice, I’m more familiar with concrete or plywood so I was really confused… Ours was built in 1974.
I have a 1942 house – the subfloor and walls are all made of 1×4 T&G. Once the exterior walls and roof were up, the subfloor was laid at a 45° angle and then the hardwood finish floor was added before any interior walls were built. All the interior walls were plastered. It was a whole different world back then.
It’s totally fine and okay to do it this way. It was done like this in previous construction. I wouldn’t recommend using felt under the backer board for the tile. You should apply thinset to the subfloor first, and then lay and screw down your backer board. The thinset won’t adhere properly to the subfloor if there is felt underneath.
You’re incredible and such a relief! So the process is: Thinset > backer board > screws into subfloor > thinset and then tile, right? No need for roofing felt or anything underneath?
Oh yeah, !
You are amazing! Thank you so much for saving the day 🤘
I’m really worried about that black substance. What is it? If it’s adhesive under the floor, it could potentially have a lot of asbestos.
It’s roofing felt 👍 I had heard that this is common in certain remodels. We purchased our home about 6 years ago and the bathroom was recently redone before we moved in
In the past, it was … tar paper, wire mesh secured to the floor\wall studs, mortar bed, tile.
Standard Operating Procedure