Three tile questions for First Project

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Old 06-30-05, 02:13 PM
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Three tile questions for First Project

First time tiling a bathroom and just want to make sure this is right:

1) On walls the cement board (hardi, Duroc, etc.) takes the place of the sheetrock, right? It doesn't go on over sheetrock if I'm down to the studs.

2) On floors, I put a layer of plywood, but also put a layer of cement board, right? Then tile on top.

3) When estimating total thickness of floor do I add something for the thinset itself? Or is that negligable? Example: 3/4" subfloor + 1/2" cementboard + 1/4" tile = 1 1/2" total?

4) If I'm trying to match level of existing hardwood in hall can I just choose cementboard thickness to change overall total as needed?

Ok, that was really 4 questions.
 
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Old 06-30-05, 04:10 PM
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1.) Use 1/2" cement board on the walls of the tub or shower surround. Other non wet areas like behind the vanity can be greenboard or sheetrock. Behind the cement board you want a vapor retarder, 4 mil thick plastic dropcloth will do. Just a few staples to hold it in place until the cement board gets put up.

2.) You have the right sequence - plywood then cement board set in thinset and anchored with backerboard screws or 1 & 1/4" galvanized roofing nails. The million dollar question is "Is your subfloor currently built to support a tiled floor?" What are the size and spacing of the floor joists, what is their unsupported span and what thicknesses of plywood do you have down now. Any and all vinyl and 1/4" luan plywood must come out first, if there now.

3.) Add 1/8" for thinset under the cement board and at least 1/8" under the tile, could be a little more depending on the size of the tile and the notch on the trowel you use.

4.) Maybe. You do need a certain thickness of plywood to start with. Once you have attained that minimum then you can go with 1/4" cement board if needed to match the height. Your answers above will help with all that.
 
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Old 06-30-05, 04:23 PM
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Thickness of Thinset Depends on Tile Thickness?

You mentioned "about 1/8 of thinset thickness, maybe more depending on the tile thickness." Thicker tile requires more thinset?

Also, I didn't realize I needed to put thinset UNDER the cementboard too. So I just trowel the thinset right on the plywood then lay the cementboard?

This floor was tiled originally - tile set in about 1/2" of cement, so it's adequate for tiling again. I'm down to the floorjoists and will go back with the needed layers as pointed out.

Thanks for your help.
 
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Old 06-30-05, 04:32 PM
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The back side of the tile may be indented with ridges that would require more thinset to give full coverage. Its not too common but worth mentioning.

As far as thinset under the boards, it is required by all the board makers. It is there to fill small indentations and air pockets between the ply and the cement board, not used for bonding the cement board to the ply, the nails do that, so you can use the cheap stuff for that, but definitely want to use modified thinset for setting the tile.
 
 

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