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Discussion Starter · #1 ·
I am fretting with progressing on tiling my bathrooms.

The area is in a 3-room bath suite (total size = 16' x 8'). We applied self-leveling compound over 1/4" hardi backerboard. (Here is where I should have done and followed my own research instead of relying on paid "help" of a carpenter working with me after hours.) This is my first post so I apologize in advance if I am giving too little or too much information.

This is a second-floor install. The framed floor is 2x10s, 16"OC with 1/2" OSB installed, then topped with 3/4" plywood, screwed down. That was done by me prior to 1999. In 1999, I had the roof rebuilt using continuous rafters, placing all the weight of the roof on the exterior walls, removing the knee wall that was previously supporting break in the the roof. Great, that took the weight off of the 2nd level floor joists and increased the square foot that allowed for the new bath suite.

When I framed all the walls, I noticed that the studs were getting longer as I went across the space, so I knew that the floor was out of level, higher nearer to the exterior walls, lower nearer the center where the knee walls had been at 8' in. Worried, I reasoned, "OK, fine, so the floor needs to be leveled. I'll figure that out later.....:vs_worry:

Although I built this house with these hands and have a ton of DIY reno/build experience since that roof rebuild, I didn't want to tackle mixing, lugging, and pouring self-leveling alone; so I hired help from contractor's employee over a holiday in the Winter of 2014. Following the lead of the carpenter, I bought the 1/4" Hardi board but we did not put mortar under the 3'x5' sheets; he insisted we should just use the recommended screws at every point designated on the boards (every 8"). And we didn't prime the backerboard before adding the self leveler. To be honest, I think we probably taped the joints since I have a receipt for a single 50lb bag of Versabond from Home Depot bought on the same receipt as the backer board, but time has erased my recall of the specifics of taping.

What I do remember is that the self-leveler did not self-level and now I wish I had run out & grabbed a metal garden rake to pull the stuff around very quickly. Instead, the carpenter used a rubber squeegee. :( The ridges were/are very small and at the time I figured I could adjust the height to flat by using the thinset when I went to install the tile. Slow-forward three years now. And here is what has since transpired.

Within a couple of months there were two long, hairline cracks. Seeking advice, most of us decided that they were just due to drying. And I have walked on the floor A LOT while installing plumbing, walls & ceilings, insulation, etc. (yeah, I know, probably shouldn't have done that, should've have left the damn floor alone until now, but here I am.) So, now there are tiny hairline cracks in many places, nothing loose. And many of the cracks align with where the joints are in the hardiboard sheets. I asked a tile shop if installing the ditra uncoupling membrane will prevent cracks in the tile once I put it down and heard, yes. So I bought the membrane and it sits next to the tub in the tub room.

I tried sanding down the ridges in the self-leveler and I'd rather dig 100' of trench for perforated pipe drain in 80% humidity than grind that floor without a vac attachment for more than 20 minutes. At some points, I tried using a brick chisel and still the ridges barely budged in height:wallbash:. If I HAVE to do that, I'll rent a grinder with a vac attachment cuz just 2-3 minutes left gray concrete dust everywhere. (I don't have any doors up and plastic sheeting did nothing to contain it!)

So here are my questions, easiest first but I'll need to address them in reverse:

a.) The floor is out of level by 1/4" over the 8' from the outside wall to the interior bath wall that meets the bedroom, despite already having added ~5/8" of self-leveler. Do I just tile over a sloping-but-flat floor?

b.) The subfloor is very solid and I'm not at all concerned about flex. And I'm confident that the 1/4" hardi board was appropriate to add. Let's assume that we also taped the joints. (We already know we did not add thinset/concrete below the hardi board, just the specified screws at the specified spacing.) Is it appropriate to add the uncoupling membrane expecting it to prevent tiles from cracking despite my seeing hairline cracks in the self-leveler over the last 3 years of it being installed?

c.) When I get to where I am installing either the ditra uncoupling membrane or the tile itself, can I simply adjust against any rippling in the self-leveler by using/adjusting the thinset and setting the tiles flat and level? (I'm using 12" x 12" ceramic tiles, backbuttering all tiles as well.)

I've put this off long enough. If I must get a flat bar and start ripping all this up, I'll cry and move on:surrender:. On the other hand, if I'm good to proceed -and overthinking this like everything else, - that's fine too:scooter:. Please advise either way. I've already beat myself up enough about this and the delay. I'm really tired of having a sick stomach every time I think of dealing with this. And I'm really tired of having to go down two flights of stairs every time I have to use a bathroom:vs_no_no_no:.
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