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  1. #1
    Join Date
    Sep 2009
    Posts
    3

    Default Best repair before tiling over a cracked slab?

    I presently have 4 in. hexagon tile that has lifted and sounds hollow underneath in a line from the wall to the toilet on a concrete slab. I plan to replace it with 12 in. tile soon. What type of repair should I make to ensure that the new larger tile doesn't crack.

  2. #2
    Join Date
    Mar 2009
    Posts
    1,387

    Default Re: Best repair before tiling over a cracked slab?

    It might be that you have a lip of the slab over the foundation wall and movement cracked the existing tile. That hollow noise is usually a void under the tile - settling causes these. So first i could remove and explore to determine what caused existing crack.

  3. #3
    Join Date
    Aug 2007
    Posts
    7,147

    Default Re: Best repair before tiling over a cracked slab?

    As Tim suggests, explore to determine the cause of the crack. When installing the new, lay down an isolation barrier. As long as the crack is stable, the isolation barrier should keep it from telegraphing through the new tile.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

  4. #4
    Join Date
    Sep 2009
    Posts
    3

    Default Re: Best repair before tiling over a cracked slab?

    Please give me an example of an isolation barrier. Are we talking about a thin metal sheet, rubber, or wood piece? Is the barrier secured to the floor or just placed under the tile? Obviously I'll be leveling the raised area. I tried to include two photos. The crack is currently sealed with silicone.
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  5. #5
    Join Date
    Aug 2007
    Posts
    7,147

    Default Re: Best repair before tiling over a cracked slab?

    I've only seen it used on a few of my jobs, so I can't be real specific about it. What I recall is that it is a fabric mesh that is laid down first, then the new tile set over the top. Check through the tiling topics, there's been a number of links posted to an excellent tile information resource, of which I don't recall at the moment.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

  6. #6
    Join Date
    Sep 2009
    Posts
    3

    Default Re: Best repair before tiling over a cracked slab?

    For those interested, I'm going to use a product recommended by Floor & Decor. It's a paste like adhesive made by North American Adhesives (NA1660) in which you embed a mesh (NA1680). It claims it can be used for "crack isolation over existing in plane cracks up to 1/8 in. with in-plane movement up to 1/8 in." It comes in a one gallon bucket which is way more than I'll need. I've already put on three coats and only used about 2 in. from the bucket. It can be painted, rolled, or troweled on. It says tile after 16- 24 hrs. dry time. The crack does run to the edge of the slab. I can't and don't want to disturb the soil around the wall. Footing for the slab is probably nonexistant or minimal here in Georgia. Unfortunately I won't really know if the crack is stable until after several seasons of changing weather. So, hopefully this works the tile goes down in a week.

  7. #7
    Join Date
    Sep 2009
    Location
    florida
    Posts
    598

    Default Re: Best repair before tiling over a cracked slab?


  8. #8
    Join Date
    Jun 2009
    Location
    The Great Lake State
    Posts
    22

    Default Re: Best repair before tiling over a cracked slab?

    membranes used for crack isolation should be tested to ANSI 118.12 ..another one to add to the mix is Nobleseal CIS. www.noblecompany.com

  9. #9
    Join Date
    Jan 2010
    Posts
    4

    Default Re: Best repair before tiling over a cracked slab?

    As Tim suggests, explore to determine the cause of the crack.

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