Ditra Heat Duo On Backer Board (Jackoboard) - Tile Advice

[OscarKnowles]

Hi,

I'm refurbishing my bathroom and looking to install underfloor heating under tiles for the floor. I have removed the old subfloor and planned to install 18mm plywood then 6mm jackoboard then Ditra Heat Duo mat with the loose lay cable before tiling. I have purchased all the materials but when reading through the Ditra booklet that came with the cable it stated the duo mat cannot be used together with foam backer board. I emailed their technical support and they said the extra 2mm fleece layer means it cannot be used as there can be 'compressibility issues'. I'm quite surprised by this and wanted to see if other people had installed the two materials together without issue? I ordered the Ditra matting as a cut length rather than a kit so I can't return it, if there is an issue would it be best to just skip the jackoboard at this point?

Thanks!

 

[Steve6690]

Duo is designed with a thermal break so that it can be installed on a concrete floor and not lose all the heat downwards. Why risk using the Jackoboard and then having an expensive floor failure? If you must use the ply then I would overboard with Hardibacker and lay the Duo on that. I would waterproof the joins in the Duo too. As you've already spoken to their tech support it might be worth running this idea by them for piece of mind.

 

[OscarKnowles]

Hi Steve, thanks for your reply and that makes sense, I will speak to their technical support again and see what they think. It's a first floor flat with wood joists so plywood seemed the best option