varnished floorboards

[maniek]

guys
i need an advice please, i got varnished floorboards and need to overboard it,
what will be better option 18mm ply or 6mm hardieboard, I would prefer to go for
hardieboard but not sure if I can as the floorboards are varnished.

[deanotile]

if there is no bounce in the floor you can use hardy or you can use an uncoupling mat such as Gmat or similar

[maniek]

im worried about the varnish, won't it make a barrier and somehow stop the addy to stick properly to floorboards???

[deanotile]

prime it

[maniek]

thanks deanotile, will give it a bit of sand as varnish is pretty thick, prime it and hardie.

[Alberta Stone]

What kind of floorboards?
How are they fastened to the primary deck?

[maniek]

t&g, nailed

[peckers]

I would give the boards a good sand with a 60 grit paper and remove the varnish as much as possible then screw the boards down (i wouldnt rely on the nails) then apply adhesive to the primed boards this takes up any undulations in the plank boards and then put on your hardi board and then screw this down.

[Alberta Stone]

Yes, sand them down to bare wood, screw them properly into place (hard to say exactly without seeing them) but you can never go wrong with adding a few more screws and going closer together with them.
A good grade of flexible thinset (with admix) to bed the hardie into and then screw down the hardi.
But this still doesn't give you the 1-1/8 inch minimum made of 2 layers of wood which is recommended.
It would be better still to screw down a layer of 3/8 inch exterior grade plywood to the deck using PL premium under it (1 large tube per sheet) and then putting ditra onto that prior to tiling and just eliminate the hardi board altogether.

[kilty55]

hi mani,i did a similar job recently in edinburgh where the boards had been varnished with some high laquer finish,sand back and prime no probs with 6mm cement boards

[maniek]

guys, thanks for an advice, the floor is solid no bounce, I'm going to use hardie..