insulation board on chipboard..

[Brindle]

Hi folks, have a bathroom floor with UFH to tile, substrate is well screwed down chipboard. I know normally you bed the ins' boards down onto flexi adi, I'm thinking it would be ok to glue (gripfill) and screw them down with washers in this instance.

What do you think? Otherwise I could advise i glue and screw 6mm b'board instead and they forego the ins' board (to alleviate any step caused)

Cheers

Bob

[diamondtiling]

No more ply, is that what you mean? If so its glued and screwed. Marmox is fixed with flexible adhesive.

If using the glue with no more ply be very careful with your mobile phone.

[Brindle]

IT is the marmox type - I know it's normally bedded in flexi adi, but I didn't want to chance putting that on chipboard you see? Unless I used a super flex adi?

[peckers]

I would prime the chipboard with an acrylic sealer or sbr and allow to dry then fix marmox boards with rapid set flexible addy useing a 6mm notched trowel

Then i would tape the joints with the waterproof tape to stop moisture getting threw the boards ..

[diamondtiling]

No more ply on the chipboard then marmox would be my choice.

[Brindle]

Yeh diamond I would rather the 6mm bboard then marmox too but haven't the height for it

[macten]

NMP screwed and glued then UFH for me

[peckers]

why are you concerned about putting the marmox directly on to the chipboard?
is it the moisture from the adhesive against the chipboard you are concerened about?
if you use rapidset then it dries out quicker.
you could use plastic ply first supplied by nicholls and clarke this has a sticky backing and will stop the adhesive coming into full contact with the chipboard and is only 2mm thick and then you could put your marmox over the top hope this helps

[peckers]

plastic ply here you go

Nicobond Plastic Ply Tile Backer 1.2 SQ.M | Backer Boards @ Vista Tiling Ltd

[Brindle]

Yes pecker it's the adi on the chipboard, I think I'll go with a super flex, marmox, ufh, tiles.
Or backer board screwed and glued and no insulation board

[diamondtiling]

plastic ply here you go

Nicobond Plastic Ply Tile Backer 1.2 SQ.M | Backer Boards @ Vista Tiling Ltd

I do not like the look of that stuff at all, it looks very flimsy.

[macten]

NMP has excellent insulation properties

[diamondtiling]

NMP has excellent insulation properties

Only if you use the premium boards.

[Dave]

You still need to screw marmox type boards to timber floors as well as using flexi addy... and use the appropriate washers and screws.