What a great forum.
I have a couple of questions. First, I have part slab, part raised foundation that meet in the middle of my kitchen, dining. Just removed terrazzo (that could not be restored due to the remodel changes)I plan to lay 18x18" limestone that will bridge a large open area of kitchen/dining/living.
How do I deal with the slab/wood seam?
Should I use a leveling compound to bring slab portion to level of subfloor-Hardibacker? (like Shaughnn describes here: http://boards.hgtvpro.com/eve/forums/a/tpc/f/2601029981...771094303#4771094303
Must all tar paper/mastic be removed from subfloor before bonding the Hardibacker?

That's a lot. Thanks for your help.

I know Shaughnn to be one of the best contractors around. I just went to that thread to check and see what he had to say, and the one thing I wanted to make sure of was there, that being that you need to honor that joint with an expansion joint (caulk joint) thru the tile. There is NOTHING that will take up that much movement difference.

Follow his directions to a "T".

As for installing the hardi to the plywood side, you want to get as much off as possible, especially the tar paper. The thinset you use under the hardi board isn't there to bond the two surfaces. it's there as more of a cushion, to eliminate vibration between the layers, thereby extremely extending the life of the floor. The screws/ nails are what attaches the hardi to the subfloor.

Thanks for the reply Bill.

You say "caulk joint"; do you mean instead of grout along that seam? So it doesn't need to be a Schluter-like expansion strip? The stone will only have a 1/16th spacer.

My thought is since it has to be an expansion joint, to look at the area at large and develop a bit of an expansion joint "grid" like the terrazzo had. Does that sound reasonable? (the stone will cover a much larger area than the old terrazzo did.)

Much apprectiated.
Don

quote:

Originally posted by lstr8or:
You say "caulk joint"; do you mean instead of grout along that seam? So it doesn't need to be a Schluter-like expansion strip? The stone will only have a 1/16th spacer.

Either or. I prefer using a caulk joint only because if you use a siliconized latex that's made by the same manufacturer as your grout to be color and texture matched to your grout, you can almost make that caulk joint disappear, although in this case, you might want to open that joint up a hair more than 1/16".

Thanks again Bill. The same color grout/caulk joint sounds like a perfect solution.
Thanks also for your great website full of insight.
Beautiful work.

If you were in SoCal, I'd turn the job over to you.
Since Ditra is not recommended for natural stone, is Hardibacker a good choice?

Thanks-Don

Just a technical clarification: the joint in your tile that occurs where the two different substrates meet is a "control joint" more than an "expansion joint". A control joint is meant to control cracking; if you didn't have a control joint, your floor would surely crack at that location. That's the primary function. I suppose it functions in a sense as an expansion joint also, since the two substrates have different coefficients of expansion, but because it's indoors, the temperatures will remain fairly constant, and differential expansion should not be an issue. What you really want to do is avoid a crack, and the joint, if placed properly, will do that.

One way or another, it's a matter of semantics, but I always thought a control joint was one manually cut into a slab to control cracking, that where two substrates meet an expansion joint is needed to account for the differing rates of expansion and contraction.

Don-- ANY CBU will do-- Hardi, Durock, Wonderboard, etc..