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Unread 02-18-2019, 08:01 PM   #81
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Join Date: Sep 2018
Posts: 210
Ok, back on the main road...

This is what's above that floor structure:
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3/4" plywood glued and screwed over 1x12 floor planks. It's not too bad out of flat. Curves with the sagging joists but actually a bit less than 1/8" over 4 feet with the lowest point right about in the middle of the floor span.
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There are a few spots where that 1/8" spacer fits under the level. Plan was to flatten it out with Mapei planipatch or similar (henry 549, etc). Mapei said to fill the seam between plywood sheets so do the big joint and the two short ones for the toilet flange patch.

There are two tricky parts:
  • The toilet flange and sewer pipe are cast iron. They were height matched to the old mud bed and two layers of tile so it's 7/8" off the current underlayment.
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    The plumber talked me out of resetting it so I'm building up to it. If I put 3/8" plank tile over Ditra or Ditra XL, I'm either left with a 0.2" gap below the flange or have to grid tnhat much off the top of the tile to make it fit under but it also depends on what angle I use to comb grooves in the mortar (and I don't know how realistic my calculations are). Also I'll have to wait and see how much the floor patch will raise the floor. Is any gap under the cast iron flange acceptable? The pipe is pretty solid and I can shim under the flange. Should I just expect to under-build it and then tell the plumber to reset the flange so it rests on the tile?
  • The tub has 1/2" plywood under it. The old planks could use something over them but I wanted to set the tub lower than the main floor so it'd be easier to waterproof that edge. I drove down to the lumber yard intending to get 3/8" for it but decided more is better so now it's barely 1/4" lower. The bottom of the tub apron is of course rounded but also recessed in and curved up in the middle. Don't know if it's some weird americast design or it got warped from all the moving, resetting and being attached to the wall. SO the gap between the edge of the 3/4" ply and the tub apron in the same plane varies from 1/2" in the middle to 1/4" on one end and 1/8" on the other. Also the bottom of the apron in the center isn't sitting on the ply but I do have it shimmed up and the tub is set in cement so it's solid.
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    The gap between 3/4" plywood and the 1/2" ply sheet under the tub is about 1/8". Plan to finish that joint was run ditra up to the tub, fill joint with kerdi-fix, and kerdi-band over that as they show in their instructional materials. However, that's a pretty wide gap and seems a bit much for the kerdi-fix. Any advice on how to handle this? (other than get a tub that isn't warped? I'm wishing I replaced it with a freestanding one to avoid all the waterproofing complexities) Can I just fill that gap with the feather patch same as the seam between 3/4" plywood panels, ditra within 1/4" of the tub apron, and seal with kerdi-fix + kerdi-band? Leave a 1/8" expansion joint along tub using gasket material?

Any advice would be appreciated.

Last edited by SpaceCadet; 02-18-2019 at 08:09 PM. Reason: fixed typos
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