[shelzmike]

So I am what I guess could be considered and advanced DIYer, but even with that, there are some things I have just never yet done. Tiling is one of them. Somehow in 30 years, it's just never been something that I had come across needing to do, somehow.

I am remodeling the bathroom and it was a complete down to studs and joists tear out. I have a few clarifications before getting started with the actual tiling.

For the floor, we tore up all the old subfloor and I sistered and blocked the joists so the floor has very little concern of deflection. It is only about 50 sq. ft.

When laying new subfloor, I used 3/4" OSB. I also flattened the joist plane by planing high spots and shimming low spots before laying the OSB. That being said, I am sure there are still a few areas that are high or low, but not by much.

I plan on using Mapei planipatch to flatten it out even further for the 6x6 porcelain tiles I will be using. I plan on putting 1/2" durock down on top of the OSB.

So question 1: Should the patching be done on the subfloor before backerboard is laid down, or should it be done after the backerboard is laid down, or does it really matter?

Question 2 is related to trowel notch size. On my shower surround walls, I will be using a rectangle 8" x 16" ceramic tile. Some recommendations I see it says use a 1/4 x 3/8 notch trowel and other places it is as the lower end of using a 1/2" x 1/2" notch, but that seems as though it may be a bit excessive.

Thanks!

 

[huesmann]

Unless you need the extra 1/4" of height, I believe 1/4" cement board is fine for floors with an existing subfloor. I would want to lay the cement board on as flat a surface as possible, so if it's easy to level your subfloor, I'd do that first.

 

[shelzmike]

Unless you need the extra 1/4" of height, I believe 1/4" cement board is fine for floors with an existing subfloor. I would want to lay the cement board on as flat a surface as possible, so if it's easy to level your subfloor, I'd do that first.

I actually do need the height. 3/4+1/2 will give me the 1-1/4" I need to meet the hardwood in the hallway very well with the tile.

I haven't checked yet for flatness on the subfloor, but it may only be a few small spots as when i was laying the subfloor I shimmed and planed the joists to get it as flat as possible.

But from my research, I am gathering that it is better to flatten at the subfloor.

 

[huesmann]

OK, if you need the extra height, have at it!

 

[jeffnc]

Self leveling normally works better before the backerboard goes down. Make sure it can't leak out through any joints into anything below. I personally would use Ditra XL as my underlayment but it's up to you. You will probably never want to go back to cement board after the ease of carrying, cutting and installing (no screws).


1/2" x 1/2" trowel is gigantic and unnecessary. Remember this is a shower wall - no one is going to be walking on it. There is no force applied to it. It just has to stick. The only reason you'd need a lot of thinset is if the walls were out of whack. Take a level across the boards and if it's flat, you can even use 1/4" x 1/4". If there are any inconsistencies you can even spot level them with blobs of thinset applied by "hand". Again you're just trying to get it to stick well and lay flat. I would use Kerdi on the walls. Kerdi Board is a little more expensive but easier. Kerdi membrane over drywall is a little more work but cheaper.