Plywood Expansion Gap

[Boondocker]

Hi all, new member here.

Some quick questions re 18mm plywood subfloor which will have 6mm insulation boards (marmox) fixed on top.

What should the expansion gap be where 2 sheets of ply meet if one is needed at all and at outside edges where the ply meets the wall?

If a gap is needed what should it be filled with to stop the adhesive used to put down the insulation board getting into the gap?

Any adhesive recommendations? I presume a single part flexible cement based one is needed.

Thanks in advance.

 

[AliGage]

Hi @Boondocker
If you're going to be insulating the Ply from your UFH it's not necessarily critical to allow for dedicated expansion in your ply. However, use a 3mm tile spacer when fixing/installing your ply sheets.
Again there is no real need to fill these joints with anything specific. Use a single part flexible adhesive to bond your boards down and this will be sufficient.