Timber subfloor for UFH mat and tiles

[jayc89]

Wardrobe/ensuite area. Posi joists are in place and I was planning on glueing and screwing 22mm P5 (Caberdek) boards to it. I want to lay an UFH mat and tile it, and have read that P5 isn't great for that. If I shouldn't use the P5 boards, what should I use instead; 22mm ply T&G? 

[nod]

It makes little difference 

[jayc89]

9 minutes ago, nod said:

It makes little difference 

 

I'd much prefer to use P5 as I already have the stuff, but I thought there were concerns around adhesive sticking to the chipboard? What would a typical build up look like if tiling onto caberdek? SBR primer, durabase/ditra, heating mat, tiles?
 

[jayc89]

Reading through a few tiling forum pages, it seems like this might be typically used;

 

- p5 deck

- SBR primer

- heating mat

- SLC to cover the mat (approx 3mm)

- decoupling membrane

- tiles

 

Does that sound sensible? Whilst the joists have been spec'd for less than 7mm deflection (4m span), I'm worried the SLC might be too brittle. Would a renovation screed like Mapei's 3240 be more suitable? 

[jayc89]

Any words of wisdom before I go down this route? @Nickfromwales @nod?