We are putting slate on our main floor, and have radiant heat. We used a second layer of plywood as guides/spacers between the pex loops, rather than concrete over the whole thing to help cut down on overall weight, as the main floor is over a full basement. We plan to fill in the gaps with thinset as we go to help with heat transfer. I'm wondering if it would be better to put a layer of Ditra down as well before we do the tile install.
Thank you!
Best Answer
Gypcrete is about 27% lighter than concrete (http://en.wikipedia.org/wiki/Gypsum_concrete). If it's not too late and you don't mind tearing up the second layer of plywood, the gypcrete will be a LOT more favorable in every way. Better for heat transfer. You can tile right over it.
That said, if you're already set on the path you're going, yes, I would use Ditra. You have to use something (a lateral anti crack membrane like Ditra, or hardieboard etc.) Ditra comes highly recommended as apposed to hardieboard. There are also Ditra alternatives that are the same basic thing (lateral anti-cracking underlayment.)