Fixing hardiebacker to plywood floor

[Rollover77]

Hi all,

I have a 18mm plywood subfloor screwed onto joists in my first floor bathroom. My plan is to fix 6mm Hardiebacker to the plywood, and then tile onto the hardie

What I am struggling with is finding a suitable adhesive for fixing the hardie, which I will then screw down too

Guys in ToppsTiles recommende their Rapid Set Flexible S1, but looking at the data sheet it says to overlay ply with cememnt board first (which is what I'm doing but need to use adhesive on the cement board!!)

I've also had the recommendation to prime the ply surface that will take the adhesive with an acrylic primer but lots of comflicting stuff online. I'll prime the underneath and sides of the ply with SBR

Can I get a sane suggestion for adhesive to use to fix the hardieboard and whether to prime the top of the ply?

Thanks

 

[cdbe]

I used the same adhesive as for my tiles (Mapei Keraflex Maxi S1) but in my case it was cement boards onto existing floorboards (probably less stable than your plywood). I primed the floor with SBR. I've had no issues.

 

[Rollover77]

I used the same adhesive as for my tiles (Mapei Keraflex Maxi S1) but in my case it was cement boards onto existing floorboards (probably less stable than your plywood). I primed the floor with SBR. I've had no issues.

Thanks, that’s reassuring

You primed the surface of the ply that received the adhesive?

 

[cdbe]

Yes,