Hi, new member here. I'm a DIY'er who is in the process of working on a second floor addition. My subfloor is 3/4" ply glued & screwed to 11/7/8" WI joists 16" oc with 5/8" ply glued & screwed to the 3/4" ply. Over this I installed Raupanel radiant floor heating throughout. I've put 3/8" ply over the Raupanel throughout except for the two bathrooms. I am asking for recommendations on what I should use over the RauPanel in the bathrooms, continue with the 3/8" ply, thinset, ditra, thinset, tile OR thinset, 1/2" cbu, thinset, ditra, thinset, tile. The main reason I am asking is because as I understand it CBU is not structural and if I go with it it will be installed over the RauPanel which is not secured, it is "floating" until the CBU or ply is installed (screws go throught the CBU or ply and through the RauPanel and into the subfloor. Personally I like the plywood because it secures it nicely but I have never used CBU so I'm looking for some experienced advice. Rehau's instructions doesn't mention CBU.

If your not familiar with RauPanel and you have a minute, the install instructions can be found at
http://na.rehau.com/files/Installation_Guide_855625.pdf

Thanks
Gary

It looks like (on page 16) that they are requiring some type of cement or mortar on top (my guess would be self-leveling compound) OR a rubber mat, like Ditra. I would probably do both, since an uncoupling membrane is usually recommended with radiant heat.

It also looks like you would secure the panels to the subfloor, then secure the underlayment to the furring strips and return panels.

Your best bet would be to go strictly by the instructions (forget the CBU) or contact the manufacturer directly for more assistance, since their advice trumps everything else.

Looks like a good system, though.

Thanks for the response Kman, I'll go with ply then ditra.