My tile guys suggests we do this, for putting down bluestone slate (1″ x 12″ x 12″) on broom-finished terrace concrete slabs, outside. All work is under roof, but exposed to year-round temperature changes, including really cold winters.
Shoot down diamond lath directly to the slab, use Laticrete thinset 4237 prepped with 333 latex additive, mud through the lath using a 1/4 x 1/4 square notched trowel, add mud as required to cover lath, set slate, grout, then seal everything.
Terraces will slope 1/4″ per foot away from adjacent house.
Sound OK?
Replies
What about Ditra to protect from slab cracks?
Billy
My guy used to use Ditra in this application, and has had his mind changed by his suppliers.
Interesting. Does he use another membrane, or did the suppliers recommend a high-flex thinset?
I guess that a membrane is one of those insurance things. You might not need it, but if you get cracks then you'll wish you used it. Even with the patio covered, it may get some localized sun heating which would add to the stress. And who knows if and when the slab will crack?
Billy
Laticrete 4237 thinset mixed with their 333 additive purportedly gives a hiflex bed. I don't know what the diamond lath is doing, but for sure it makes the setting bed thicker by at least the lath's own thickness.
That's a good thinset mixture. Some people say that the diamond lath in thinset is a bad idea because it destroys some of the bonding area, but I don't know firsthand.
Billy