Hi guys, looking for some answers to help me with the prep of a bathroom floor, been looking at posts and talking to the local tile shop and have now got very confused, we plan to have 10mm porcelain tiles with UFH , so far I have removed the old 18mm chipboard , replaced it with 18mm WBP pl, with 3x2 noggins at 400 centres screwed down every 200mm,the ply was not as good as it should have been for the money but it's down now,should I prime the ply if so what with?
Have been told 10mm marmox screwed down also 6mm marmox on tile adhesive !
Do I need to bed marmox down onto adhesive , 6 mm will this be ok as don't want excessive height also should I also screw the marmox down ? When this is down what is my next step cheers for your help

Hi and welcome to the forum!

You need to screw AND glue the boards down. The adhesive will fill the voids under the boards and the screws are there to fix them down.

Cheers Rich thanks for the info, could you recommend which adhesive i should use , also should I prime the ply would I gain much by using 10mm marmox over 6 mm ? Thanks again

underside of ply and edges should have been primed. i would go for the 10 mm board if you can get away with it , height wise. glue down with spf addy and screw

As above

If you are unsure if the face of the ply needs priming, then you should check with the adhesive manufacturer (it usually says on the bag) as some recommend that you prime the face and others say just the under side and edges.

So you think I should take the ply up and prime the underside and edges if recommend by manufacturer or find adhesive which only needs face primed, what is the purpose of the primer, also what is SPF addy? Cheers

Wow just looked at the BAL & Mapei sites more confused which adhesive to use!

A good single part flexible adhesive. The primer does two main things, it reduces dust and it stops the substrate from absorbing to much moisture out of the adhesive.

It wouldn't hurt to seal the underside and edges of the ply but to be honest I dont think i would bother taking it all up again if it has already been fixed down.

over time we have heard about up to 20 + different manufactures. Always make sure it has the 'flexible' in the title.

Warm regards,