Acrylic Primer Mix Ratio for Screed Floor / Tile Backer Board

[Johneb]

Hi, As a (reasonably competent!) DIY'er undertaking a complete home renovation, I've found this forum invaluable for picking up advice from the experts. However, I've come up against a minor problem that I can't find an existing answer to and should be very grateful for your words of wisdom: I'm about to tile a conservatory floor which has a 65mm 4:1 sharp sand/cement screed over underfloor heating. The screed has been left to dry for four weeks, then two with the heating on. I've vacuumed up the loose surface granules and primed with 3:1 ratio Granfix Acrylic Primer, but have been advised that I should use a 1:1 ratio - what do you recommend, please?

Also, my next job will be to renovate the bathroom, which has the original (1930) pine floorboards. I was originally going to cover this with 12mm marine ply, but my wife objects to the relatively large increase in floor level, so now I'm considering 6mm 'No More Ply' backer board. Is this material as good as the manufacturers claim? I'll be covering it with 300mm square porcelain tiles.

Thanks in advance

John

 

[White Room]

Hi and welcome......6mm Hardie would be my choice but I hav'nt used no more ply but seems a similar product, make sure theres no bounce in the floor.

Hardie would need a single part flexible with 4-6mm trowel and screwed to the boards,25mm turbo gold from screwfix is the ones I use.

 

[John Benton]

As above, I've used both NMP and Hardie but make sure that pine boards are checked for deflection and any squeaks. Screw down where the squeaks are (too late once its tiled).

 

[Rookery]

I've used both but prefer Hardie. I find NMP more brittle. Re the primer, I dont use Granfix but I'd expect a 1 - 3 dilution ratio to be satisfactory. What does it say on the container?

 

[Johneb]

Thanks Rookery. The container says 3:1, but the adhesive manufacturer's (Ultra) tech department suggested 1:1 would be better. I appreciate they should know best, but I'd prefer the opinion of guys who actually work with these materials and can advise from experience!