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I’m installing porcelain tile over a stable concrete slab for the first time. Does anybody have recommendations on the pros and cons of using thin-set mortar vs. a mastic adhesive? Also, what is the best way to clean and prepare the concrete slab prior to installation (there is currently sheetrock mud and paint all over the slab).
Thanks in advance for any suggestions or advice.
Rex Linville
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Rex, Since nobody else wrote I figured I would. I am not a contractor, but have laid my fair share of tile. Besides, I am Italian, which means I should have a genetic disposition to tiling.
The adhesive can be either/or depending upon the size of the tile. Small tiles are ok for mastic, but not big ones (I think the limit is 8" on a side - look at the direction on a can of mastic). I believe this is because the mastic compresses more than thin set so large tiles will crack due to deflection (they don't bend so well).
Even though modern mastics, (and polymer modified thin set) even the water soluble ones, stick like crazy to anything, you should clean the floor of dust and especially drywall mud. I don't think paint should be much of a problem unless it isn't well stuck on itself. I have tiled painted basement floors with good effect.
I usually use a good quality thin set plus a polymer additive or a thin set with the additive built in for floors. Walls are much better done with mastic because it sticks so well the tiles don't fall off before it cures.
Don't buy cheap thin set and do use the additive. I once had to pull up and redo a floor because the thin set didn't bond to the tiles. Of course the tile guy blamed the thin set, the thin set people blamed the tile ..., you get the picture. Good thin set works amazingly well. I tiled on top of tiles about 15 years ago with a good thin set plus additive, and the tiles still hold up perfectly.
Good Luck.
*1. Do not use mastic. It is not appropriate for tile concrete bonding. Use a thinset with a latex additive.2. Use an isolation membrane. Concrete slabs expand and contract at a much different rate than tile, and your grouts lines will crack along cracks in the slab. Go to a good tile store or masonry supply store and ask for an isolation membrane. Should run you about $1 a foot. You peel and stick it to the slab, and tile on top of it.
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I'm installing porcelain tile over a stable concrete slab for the first time. Does anybody have recommendations on the pros and cons of using thin-set mortar vs. a mastic adhesive? Also, what is the best way to clean and prepare the concrete slab prior to installation (there is currently sheetrock mud and paint all over the slab).
Thanks in advance for any suggestions or advice.
Rex Linville