cracking grout


Old 05-19-03, 05:17 PM
brent h
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cracking grout

I recently installed a ceramic tile floor on top of durrock. I took care to keep the seems tight on the durrock, and securely attached each tile with mastic. I have been finding cracks in the grout, and have noticed a slight give to the floor under weight.
the joises look OK- I think it is just from being an old house that has been through 2 major earthquakes. My question is, can I use Caulk or something else that would be more elastic than sanded grout? I dont have concerns about the tiles popping off, the movement is barely noticable, even when looking very close. Its just enough to start small cracks that concern me. thanks
Old 05-19-03, 06:43 PM
Join Date: Sep 2000
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1. Seams should not be tight on DUROCK. You should leave 1/8" gap and tape the joints with cementboard tape and thinset.

2. You should use thinset under the DUROCK, and secure it with hundreds of screws.

3. Floor tile should never be installed with mastic. Only thinset should be used to adhere floor tile.

4. Tile should not be installed on any floor that has noticeable give to it. Calculators are available to compute the deflection from the size, spacing, material and span of the joists.

5. You must have at least 1.25" of flooring between the joists and the tile.

6. Grout should be mixed with as little water as necessary to get the material damp. No additional water should be added after installation begins. And cleanup should not add any more water. If the grout is too thin, it will crack when it dries.

I do not recommend trying to repair the cracks with caulk. If they are small, I'd say just live with them. When they become big, cut out the grout and regrout.

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