I have been trawling all over the forum for a definitive recommendation on fixing 6mm hardie backer board to a failrly solid 22mm thick t&g wooden floor but I cant find the answer anywhere - even on the thread where the hardie rep introduced himself and then disappeared !

I just went to my local Topps to get a hardie knife and they said just use screws - 100 hardie screws for £6.99 - yeh right

I suspect the answer is bal spf with deck screws but if someone could confirm I would be grateful

btw great site

I'm not 100% sure, but i think it can just be screwed down.

But the BS for tilebackers for floors is a minimum of 10mm, no matter what hardibacker tell you.

I've used the 6mm on small floors with no deflection, Spf and screwed with screwfix turbo screws 25mm for support.

Just to throw a spanner in...Mapei say they will guarantee 6mm hardi with there adhesive..

Thanks Whitebeam - the floor is just over 7m2 - is that small ?

Almost everywhere I have looked, the advice for solid wood floor in preparation for ufh and tiling and where 18mm ply is too much height, is 6mm hardie

Check this site http://www.jameshardie.co.uk/pdf/ins...eBacker250.pdf

Originally Posted by Dave

Just to throw a spanner in...Mapei say they will guarantee 6mm hardi with there adhesive..

On all their adhesives?

thanks for the responses so far - i checked the hardie web site and it says

"HardieBacker™ 250 cement board is bedded into a tile adhesive compound."

It doesnt say what type of tile adhesive and thats why I asked the forum

As far as I'm aware pugwash. If you're fixing backerboard onto timber you'll need to screw as well. Adhesive alone won't be strong enough.