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Repairing concrete subfloor under bathroom tile?

Repairing concrete subfloor under bathroom tile?


  #1  
Old 01-11-08, 09:18 PM
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Repairing concrete subfloor under bathroom tile?

I'm planning on redoing the tile in my bathroom. Right now there are a few cracked tiles near the edge by the door, and I can see it's concrete underneath. Parts of the concrete are cracked pretty deep. What do I need to do to repair it and prepare it for new tile?

I tiled my kitchen before, and I put some wonderboard underneath the tile, do I need to do this for the bathroom too? I'd rather not raise the height of the floor too much. Can I just repair the concrete somehow, and lay tile right over it?
 
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Old 01-12-08, 04:49 AM
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If you have a concrete base under the tile, it usually does not require anything else as an underlayment. But bad concrete makes a bad tile job. If you are sure the only bad area is around the door, you could break it out and add a floor leveler compound to the level of the existing concrete, then retile that area. To avoid raising the floor any, you would have to chip off the old tile or dig out the concrete/tile and start over. Keep in mind that the underlayment/subfloor for a good tile job must be thick and RIGID, min of 1 1/4" is usual. You can retile over existing tile, but the old tile must be absolutely clean, and the surface scuffed to add tooth for the adhesive(thinset)
 
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Old 01-12-08, 05:04 AM
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To some extent you can control the propagation of concrete cracks to ceramic tile above by installing an isolating membrane, see for example:

http://www.nacproducts.com/

This works best if the cracks are 1/16” or smaller and there is little if any vertical displacement of the slab.

Installation is straightforward, but the material is fairly expensive, especially for small jobs as you generally need to buy an entire roll of material and a full cans of the primer and adhesive.
 
 

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