[onely]

We are about to install a wire system of radiant heat on the plywood on the bathroom floor. We have tile to put over it. The brand is Warm surfaces

I have been doing a lot of reading but I am getting mixed answers.

We are thinking it goes in this order.

Draw the pattern on the plywood. Install according to instructions.

Put self leveling compound on top and allow 24 hrs to cure.

Put thinset on top of self leveling compound then Ditra the more thinset then tiles.

How does that all sound. Thank you.

[Bljack]

If you had heat mats, wire embedded within a mesh, I'd say you have it pretty much under control, just don't forget about the primer you need to brush over everything before pouring the slc, but...

It sounds like you've got just a plain wire type heat mat system, is that correct? If so, then over plywood, you'd want to follow exactly what the self leveling cement manufacturer specifies. While the heat manufacturer might say to bury in slc, they won't mention all the slc detail because they don't make the slc.

Over plywood, slc needs to be poured to a minimum thickness anywhere from 3/8" to 1/2" thick, and needs to be poured over lath. Now sharp metal lath and heat wires just don't mix and trying to walk across a combo of both of them is going to tear your wires apart and render the system useless. You will need to find either Custom Lath From Custom Building Products or Mapelath from Mapei. Both are plastic laths designed for reinforcement of slc over plywood when the use of metal lath would be contra indicated, such as with the application of heat cables.

If it was going on a slab or cement board, you wouldn't need the lath. You could lay 1/4" cement board in thinset and screw it down, then tape the joints, then lay the heat wire on that and prime and pour with out needing anything deeper than reaching the top of the heat wire. Ditra over heated floors is THE way to go with the rapid heating and cooling cycles. Good choice.

And don't forget the primer, all slc's have one!! Use a brush to apply it, not a roller. Rollers allow the SLC primer to puddle, brushes don't.