Replies

1. GBA Editor
   Martin Holladay | Apr 20, 2013 06:35am | #1

   Mark,
   What you need is a layer of Schlüter Kerdi-Board or Wedi Building Board - two brands of polystyrene tile backerboard. Either product is available in 1 inch or 2 inch thickness. They provide R-value and tile backerboard in one product. Two inches would be much better than 1 inch, if you can find a way to go that route.

   More information here: Tile Backerboard Options

2. 
   mk10 | May 01, 2013 12:36pm | #2

   Is it posiable to use 25psi xps, plywood, backer board combo? I actually have about a max of 1.75" to play with (plus the slate thickness).

   If so what would that look like? How would i adhere these?

   Also instead what about adding electric radiant heat to kill the chill? seams like it would be expensive to run but i read somewhere i'ts about .30c a day, hard to belive...it's a mudroom.

   Thanks!

3. GBA Editor
   Martin Holladay | May 01, 2013 01:13pm | #3

   Mark,
   Q. "Is it possible to use 25 psi XPS, plywood, backer board combo?"

   A. Yes, but why do you want to do it that way?

   First of all, if you are installing backerboard, you don't need the plywood.

   Even easier would be following the advice I gave before: use a backerboard that includes foam insulation, like Schlüter Kerdi-Board or Wedi Building Board. Then all you need is one product instead of three.

4. 
   mk10 | May 01, 2013 04:31pm | #4

   well the fancy board you suggest would be great if it was readily available in small quantities but its not so I revert to the poormans solution, use what I got.

5. GBA Editor
   Martin Holladay | May 01, 2013 04:33pm | #5

   Mark,
   OK. You can use old-fashioned cement backerboard and XPS if you want. But you don't need the plywood.

6. 
   mk10 | Jun 29, 2013 10:03am | #6

   Hi Martin, so i thought about what you said earlier and you are right why would I use three products instead of one? well tried and tried to get the wedi board and they require a min order as they do not stock 1" (and i also found out that Schlüter does not recommend Kerdi-Board for floor slate/tile installations although they are testing now). I talked to the rep for this area and i am sol unless i want to spend more than I need so its back to my way with a few more questions.

   does it make a difference if I use 1/2" Hardi Backer or the old fashioned cement backer board, for some reason i like the hardi backer.

   Should I tapcon the assembly to the floor or just use a thinset or both, i was planning on using just tapcons. (also of note there is existing textured sheet vinyl solidly attached to the slab).

   Thanks for your help, or any one else for that matter!