Radiant floor heat / slc questions [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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bob korczakowski
02-21-2008, 06:28 PM
Good evening

Im tiling a bathroom floor and have a few question about what steps are needed to install a heated floor (nexans cable) let me explain what i have going on ,please let me know if im on the right path

heres the plan
16 in oc 2x12 joist with 3/4 plywood
thin set (modified )with 1/4 durrock
wire mech (if needed ?) then heating cable (nexans requies to cover cables in slc )
Prime 2 coats
Pour slc ( smooth start slc requies a metal mesh )
Also not sure if i should use ditra over the slc
and last to lay 12 x12 ceramic (modified over the slc, unmodified if i use ditra)

Also i just used kerdi shower systems for the first time,it work out great but it took me a long time to tile the shower using 4x4 tile

Any advice would really be a big help


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02-21-2008, 08:14 PM
I'd consider omitting the cbu, and pouring a slightly thicker slc pour. It will be much easier to anchor the cables to the subflooring rather than through the cbu. If you pour it over the cbu, you don't need the lath, but if you do it on the floor, you do. I'd not use the metal lath with the heating wires, I'd use custom's duralath. SLC is not cheap, but it does level better with a deeper pour. Ideally, it is 1/2" over the highest point. Then, you can tile directly on the slc, or use Ditra.

Don't forget the slc primer...it is essential to a reliable pour.

02-21-2008, 08:43 PM
I'll second Jim's comment and add what I tell my customers. In the event a tile needs replaced it's alot easier and safer to remove it from a 4000 psi slu than the alternatives which lead to the risk of needing a patch for your warm wire. I don't think you need the ditra. Might use a roll on over the slu like Red Guard or WP-6000. Less expensive, while providing some extra protection from slu cracking.

bob korczakowski
02-22-2008, 04:59 PM
Thanks for the quick response!

so with cbu down i wouldn t need a lath?

I just laid down the 1/4 durrock today
but i think i'll go with laying down the ditra over the slc (price wise its only 70sf of ditra, not that bad

Thank again for your help

02-22-2008, 05:43 PM
Lath is required for over a plywood subfloor. After you have cbu down, it's basically a cement floor. Adding lath would strengthen it, but I'm not sure if it is enough to worry about. Fastening the lath down could be a pain, but it would give you something to tie the wire to. Read the fine print on the slc instructions and see what the others have to say. You need the primer, regardless.