hardibacker i am confused

[kevemo]

always used ply for overboarding but now thinking of tryin hardibacker after problems with height isues prob is not sure how to use it ,guy in tops tiles reckons for over boarding tounge and groove floors you need a thin layer of adhesive [4mm notch] then 6mm hardibacker screwed down every 200mm and then tile straight on top said this will be fine as good as 12mm ply is this right

[tfs]

shouldnt be compared to ply in my opinion but it has benefits that ply doesnt.

As long as the tongue and groove is solid, no bounce and well fixed to joists etc then straight over will be fine.

I would go for a bigger trowel than 4mm though!

[Sir Ramic]

It will add no strength. But pretty much correct info for fixing but trowel size will depend on how bad the floor is. i usually go over the T&G with back of trowel then spread the floor. lay boards and screw down.

[tfs]

Many salesman are under the impression that 6mm hardieback becomes as strong as ply once adhesive has set. Im afraid this is not the case.

[kevemo]

cheers for the quick replies
thought i sounded a bit to good so wots the solution to get the same strength then ?

[tfs]

just ensure that the floor is well screwed/ fixed to the joists prior to installing the backer board.

Failing that, its a matter of doing the same as you would normally do, whether this be oversheet with ply, replace floor boards with ply or add additional noggins and packers to the joists etc

[Sir Ramic]

15-18mm Plywood

[kilty55]

cheers for the quick replies
thought i sounded a bit to good so wots the solution to get the same strength then ?

kev,as long as the sub floor/tongue and groove are sound and solid then a 6mm trowel bed and 6mm cement board shall be fine for a floor screwd down

[kevemo]

cheers for the replies my main reason for changing to 6mm hardibacker is i just seem to be getting a run of job quotes were the customer is adamant they dont want the floor height raising to much no matter wot advise i give ,walked away from 2 this week but cant afford to keep doing this so trying to find the best solution

[Bathfix Bob]

The worse thing about screwing the subfloor down again to strengthen it is you never know where ALL the pipes are, I always cut out a section and check (I also have an LCD inspection camera) where the pipe runs are.

I fitted a bathroom back in March and got a call to go back as there was hot water pouring through the dining room ceiling, closer investigation revealed that I'd managed to screw into a 22mm hot pipe from the cylinder (gravity). It had been watertight for months until the screw had become eroded/corroded by the water.

Lesson learnt, never again!

[Perfect Tiling]

I never use plywood. The stuff stocked local to me all has a final layer of hardwood and i've done samples of gluing tiles to it and leaving for a week or two. It always comes off easily...but can't remove from the hardibacker. I usually drill a hole in the existing floor and measure the thickness so I can use screws that won't protrude through the underside. Clean the timber and apply adhesive with 8mm trowel. Lay the hardibacker so joints are staggered, screw down at 250mm centres and tape and fill joints with adhesive. When tiling I usually wipe the area as I work with a wet sponge to remove any dust and wet the surface. Seem to work for me OK..

[Ceramica Tiling]

12mm ply with bal fastflex, try a test patch and see if it sticks :-)

[Perfect Tiling]

OK...will do...but as I said it seems to be the ply up here and not the adhesive. Just won a load of BAL supercover flexible so can try that as well. Cheers for the advice.

[Oli]

The worse thing about screwing the subfloor down again to strengthen it is you never know where ALL the pipes are, I always cut out a section and check (I also have an LCD inspection camera) where the pipe runs are.

I fitted a bathroom back in March and got a call to go back as there was hot water pouring through the dining room ceiling, closer investigation revealed that I'd managed to screw into a 22mm hot pipe from the cylinder (gravity). It had been watertight for months until the screw had become eroded/corroded by the water.

Lesson learnt, never again!

Excellent advice, I once got complacant and put a screw straight into a gas pipe, lucky not a customers house, but at my grandads after the council had just done a refurb, of his bathroom and not bothered to refit the carpet gripper threshold in the doorway, they had lifted some floorboards and not fastened them back down so I screwed them, strong smell of gas, undid the screw.... hissssssss. Oops.

Luckily my cousin was also there and he's a gas fitter so no panic, just turned the gas off and he replaced the pipe section. Could have been a disaster.

[whitebeam]

I use screws that don't protrude thru the boards, mine are only 25mm for the 6mm hardie