Replies

1. 
   manoman | Dec 09, 2006 08:23am | #1

   If you have time to test a patch of tile installation, even one tile, you would see if the tile will stick to the floor. Sometimes a scratch coat of modified thinset cut with an acrylic bonding agent will help the bond. I have used KeriLastic products with success. To remove any doubt, though, grinding it back to the raw 'crete is probably best. Dust collection becomes the big problem on an interior job. Do the grinding first before anything else goes in there. Good 'at source' vacuum collection is best.

   Bridging the cracks, which are acting as control joints, is a riskier proposition. If there is any movement at all, the tiles will crack. How old is the floor? Has any settling/cracking occured yet? Designing around these cracks, ie putting a grout line along the control joint and caulking it, or fitting a brass strip into the joint and tiling up to that.
   To bridge it would require a fibre-mesh strip like the stucco guys use, laid in a bed of thinset. Even this won't with stand cracking.

2. 
   maggie2142 | Dec 09, 2006 03:52pm | #2

   Sounds like an ideal application for Ditra:

   http://www.schluter.com/english/products/2002/sectionf/ditra/601-ditra.html

3. 
   danski0224 | Dec 09, 2006 04:06pm | #3

   Saw some commercial tile setters use a roll-on blue colored product onto concrete and embed what looked like fiberglass mesh into the blue stuff.

   The tilesetter said it prevented the tiles from cracking and he said it works. The blue stuff was troweled into the control joints on the ground floor and rolled onto the rest of the floor.

   The tile used was 18" square porcealin.

   I don't remember the name of the blue compound, but it should be available at any professional tile shop. It was premixed in one gallon cans.

   The concrete on the job where the tile was set was not sealed.

1. 
   zak | Dec 10, 2006 01:06am | #5

   I think several companies have "uncoupling membranes" like that, which bridge cracks, and let the slab shift a little bit without cracking the tile.  I'm sure laticrete and custom make them- a roll on or trowel on product, with a sheet material over it.

   I think it's the way to go for the op, too.zak

   "When we build, let us think that we build forever.  Let it not be for present delight nor for present use alone." --John Ruskin

   "so it goes"

    

4. 
   FLA Mike | Dec 09, 2006 07:55pm | #4

   Just a thought.  Depending on the thickness of the laminate floor vs. the tile, and whether you need to build up the tile floor to achieve a matching thickness w/ the laminate, going with cbu over the slab may alleviate having to deal with the sealer.  I'd still use Ditra under the tile no matter what. 

    

    

   How do we dance while our world keeps turning? 

    

   How do we sleep while our beds are burning?

    

    
5. 
   pinko | Dec 10, 2006 03:28am | #6

   Ditra, and be done with it.

6. 
   custombuilt | Dec 10, 2006 06:07am | #7

   Don't sweat it, just get a chisel and chip the floor every 8 to ten inches or so and use modified thinset, then buy youself some schuyler ditra and run a strip over that joint, a tile with on both sides.

    

    

    

   When in doubt, get a bigger hammer!