Subfloor question [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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01-25-2004, 12:14 PM
I'm a lucker here, trying to learn so I can ask the approriate questions for my project.

We are re-tiling a smaller 3/4 bathroom. The current tile [20 years old], has cracked around the toilet. I think this is due to the previous owner overtightening the bolts as the floor does not feel spongy.

I took off the heat register and measured about 1 in subfloor with about 1/4 cement backer. The joists appear to be 16 inches on center 2x10's. Our house is a raised ranch and the basement ceilings are finished.

With the bathroom floor measing 5.5'x5.5', should I be ok with this much subfloor? I am not planning on tearing out the neo-angle shower stall, so there is little tile area.

Once I tear out the tiles I will get a better feel for the quaility of the existing subfloor and have more details [is it ok to replace the subfloor everywhere but under the shower, which does not leak?]

Next question is that the existing tile is about 1/4 " thick [2"x2"]--the tile we have been looking at appears thicker [6"x6" size] The bathroom is about 1/8" lower then the adjacent wood floor for the next room. Should I be looking at a thinner tile to maintain an even floor height?

Any thoughts as to what I may not have thought about yet? The only tile work I have done so far was a kitchen back splash which turned out pretty nice.


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01-25-2004, 02:16 PM
Is the subfloor plywood or planks? It matters because plywood is more dimensionally stable than planks. Your cracking may be the result of swelling in the subfloor from a past toilet leak. If plywood, then 1" is plenty. If planks, we'll need to add some plywood.

When you demo the floor, go ahead an plan on tearing out the backerboard. Chances are you will damage it removing just the tiles, and ripping the whole thing out will be easier anyway.

Do the joists span more than 14 feet? Probably not, but I always ask.

Let's not jump to conclusions about replacing the subfloor. You may just have to patch in a couple of spots. But it is possible to do only the tiled areas if needed.

Height differences between one room and another are common, so don't sweat it. A wood transition strip will handle it.

01-25-2004, 06:56 PM
I'm 99% certain that it is plywood. I was assuming that I would damage the backerboard and have to replace it---I only want to do this once so I want to do it right ;) .

As far as the joists, I believe they are 12 ft spans max, based on measuring the bathroom/adjacent kitchen width [as the joists run].

The guy at the flooring store also mentioned that a wood transistional strip should work fine...he even recommend another place that has more variety for the strips.

I think I have everything set now in my head...just a matter of demo'ing the floor and verifying what I have.

Thanks for the help

John Bridge
01-25-2004, 08:12 PM
Welcome, Jake. Don't be a stranger. ;)

01-25-2004, 08:14 PM
Welcome, Jake. :)

If your current tiles are 1/8 lower than your wood flooring, and you plan to use thicker tiles, sounds to me like you might be getting better rather than worse. If those 6x6 tiles are ceramic, I doubt they'll be thicker than 3/8ths of an inch. I could, of course, be wrong about that.

It's pretty unlikely that a fella could have cracked properly laid tiles by tightening the toilet flange bolts. I think we should find some other reason for those cracks when you start tearing stuff out. Let us know, eh?