Under floor heating mat on chipboard floor

[Bri]

Hi folks,

Got a job in a couple of weeks where the customer wants under floor heating. Just wanted to know what best practice and materials are for this job ie, ply, then mat, then a flex slc over, then tile with flex adhesive/ grout etc. Substrate is 22mm chip board screwed to joists, tiles are ceramic. Not done this before and just wanted some opinions. Thanks in advance. Brian

[Sir Ramic]

I would be using a cement backer board if the floor was solid enough. Lay the UFH mat then SLC. SPF adhesive and flexible grout.

[Bri]

I would be using a cement backer board if the floor was solid enough. Lay the UFH mat then SLC. SPF adhesive and flexible grout.

What thickness backer board would you use? is 6mm enough, or 12mm. Always used ply on wooden substrates, is the backer board easy to cut and install etc. I assume it needs pilot holes before screwing, please correct me if i'm wrong!!!

[aph257]

as above but if your concerns are the difference in levels of floors, there are threshold plates that are adjustable to suit.

[Sir Ramic]

Assuming the floor is free from deflection then 6mm backer board is sutable. Pre drilling is not necessary if you use the correct screws and it cuts easy with a special scriber.

[Bri]

No issues with threshold height, just stability i'm after. All the adhesive manufacturers say 15mm minimum with ply just wondered if there was a minimum for this product. Thanks for the quick responses

[doug boardley]

If floor is deflection free and height is not an issue, I'd be inclined to use 10mm insulation board, then ufh mat, flexi slc then addy and tile. If the tiles are stone or if a large area I'd also use a de-coupler on top of the slc.