Replies

1. 
   sawdust_steve | May 01, 2020 10:49am | #1

   Have you looked at self leveling compound? It can be poured on top of the cement board and will self feather down to zero

1. 
   drew_z | May 01, 2020 11:40am | #2

   I haven’t used that before but seems like it Could be Exactly what I need. Do i need to worry about an uncoupling membrane layer under the cement board so the cement board / self leveler / thinset / tile all ‘floats’ on top of the framing and subfloor? Or is the self leveler providing that break?

2. 
   jlyda | May 01, 2020 12:06pm | #3

   The way I like to do a tile floor is to start as you have w/ 3/4” glued and screwed to joists. I follow that with 1/2” plywood glued and screwed, stagger seams from the 3/4”. If that is flat enough I install a waterproofing crack isolation membrane (I prefer the wet type) over the plywood. If the floor is off a lot as yours sounds like it is, I pour self leveling compound on top of plywood and apply membrane on top of that. Follow the instructions exactly for the compound or you will run into trouble. Also, I usually place a screw at the lowest point of floor at level, so I know when to stop pouring. You typically need to cover the entire floor for it to level off properly. Also, the mix is really wet, so you want to seal all edges, seams etc as the compound will spread and leak like a bucket of water. Use a clean garden rake (not leaf rake) to comb the pours together. It will level on its own, but raking is important as you need to combine the pour between bucket dumps. Also, get yourself organized before you start. You need to work fast with mixing and dumping. It’s sets fairly quickly, so can’t mess around. You will probably need to do the job in 2 pours, most of the compounds I’ve used do not allow for 1” or greater in one pour.

3. 
   edwardh1 | May 01, 2020 05:56pm | #4

   its pricy but works. like pancake batter

4. 
   andy_engel | May 02, 2020 06:42am | #5

   There was a good tip in the magazine recently: https://www.finehomebuilding.com/2018/11/07/the-secret-to-leveling-subfloors

5. 
   firedudec56 | May 03, 2020 07:52am | #6

   any idea on what made the floor "bowl-shaped"? if that problem isn't addressed, you may make it "flat" now & later it moves again.
   other question is how much "height" do you have to work with in raising the floor thickness? Is the edge of the tub made to be buried in the floor?

1. 
   drew_z | May 03, 2020 12:11pm | #7

   Thank you all your the advice.

   I started to lay out the shape with screw heads to establish how much material I would need and realized it isn’t a bowl shape but a fairly flat, if slightly sloping, floor with a huge swale against the Exterior wall. The overall slope is due to improper footings (house was built in 1903) that I have replaced coupled with posts removed to make the basement more spacious at some point, which I’ve also replaced.

   The large swale is because the blocking the plywood secures to on the exterior wall is 1/2” higher than the rest of the framing. It appeared to have to be set this high to clear the lines feeding the radiator and it is not in the budget to replumb those lines. So i got out my power planer (I am a cabinetmaker by trade and default to woodworking solutions) and planed down some of the plywood and got rid of about half of the issue. I think I will now offset the seams And glue and screw 1/2” ply down on top of the existing 3/4” plywood, fare out the plywood a bit more with my plane and then install my cement board.

   Thank you all for your help again!

6. 
   firedudec56 | May 03, 2020 04:15pm | #8

   any chance of adding "framing " material under the 1/2 inch to make it level?