Tiling over uneven subfloor

Old 11-08-06, 06:45 PM
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Question Tiling over uneven subfloor

Hi, I am about to lay ceramic (or possibly porcelain) tile over plywood subfloor in my 30 year old house. The floorboards beneath the plywood have dipped slightly just inside the front door. The dip is nothing major, but obviously I'd like the floor as level as possible before I lay my new tile. As I'm not in a position to replace the floorboards (which run diagonally), would some type of self-levelling compound do the trick or would any other remedies be more suitable? Thanks.
Old 11-08-06, 08:49 PM
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Provided the floor is still solid, a self leveler should work. But first investigate the cause of the problem. If the floor is weak in that area, you'll just be causing yourself future problems. If it is good and solid. I normally use level quick. Mix it pretty soupy, pour it into the area to be leveled, make one screed pass, and leave it alone until it dries. I use Ardex Feather finish to feather the edges out but that step is probably not needed in your case. The thin set should do that. I do have to ask a question before I quit. Are you planning to put down concrete board over the plywood? If not, you're wasting your time and money. Without concrete board between the tile and wood, the tile won't stay there. Tile and wood have dramatically different expansion and contraction factors and the concrete board compensates for that. If you have height issues, use quarter inch instead of half, but don't skip the concrete board step, it will not have a good outcome. And follow the instructions for installing it. Thinsetting it to the floor is not optional, it must be done, otherwise the tile will begin to crack or come loose down the road.
Old 11-10-06, 11:17 AM
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Before you do anything, you need to find out why the boards are "dipping" and fix the problem. I agree that using cement board is the way to go. One change though. Do any necessary leveling on top of the cement board not under it.

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