Got a job coming up soon, about 12 m2 trav, the existing floor is firm ,flat and stable, its floor boards covered with hardboard and then vinyl, once ive removed the vinyl would i be able to screw 6mm hardy boards straight on top of the hard board, i wasnt planning on using adhesive, only screws so there shouldnt be any danger of the hardboard taking on moisture...?

kev

You would be better laying min 15mm exterior ply, followed by Hardie board glued and screwed

i was assuming that as the floor is firm and stable i would not need any ply? just possibly the hardy board screwed over the existing floor?

Hi Kev, BS. states 15mm ply I don't think Hardie boards alone take out deflection

as above

If the floor is firm I would take up the hardboard as well and use a spf with the 6mm hardie and screwed......

Would'nt use just screwed hardie

Hi..

If the floor is stable then remove hardboard and use Hardi with adhesive then screwed.. works for me..

yep remove hardboard and glue and screw hardie

Maybe I go OTT with prep, but I always like to (err on the side of caution)