Another hardibacker question

[mz30]

Am doing a job for my aunt at the weekend.
Remove old tiles and 6mm ply to floor boards as it has failed (surprise,surprise).

Now as i have had nothing to do with the material side of things as i was only called about it after they had bought everything,the guy from ctd has sold her 6mm hardibacker to replace ply.

Having never installed hardibacker on floorboards(i usually would use 18mm marine ply or wpb)is the hardibacker suitable for said job and if so would i need to screw it every 150mm as i would with ply?

Thanks for any input.

Oh the tiles are 600x600 polished porcelain and the area is around 8 m2.

 

[Dan]

Not too sure personally but here are the installation instructions: Backerboard Installation | James Hardie United Kingdom

 

[mz30]

Thanks dan,like i thought the floor still has to be plied ,hate salesman cost my aunt £80 then if she wants it still gonna have to fork out £70 + for ply first.

Will have to break the news to her lol.

 

[macten]

Can go straight onto the floor boards if sound and solid - no need for the ply.

 

[Dan]

Make sure you use their screws though. It seems that's important.

 

[mz30]

Can go straight onto the floor boards if sound and solid - no need for the ply.

But the website dan linked says it needs to go on ply? not sure if i would trust it with floorboards in a bungalow that has already had a failed floor,i will secure all floorboards ,but until i remove the exsisting am sort of going in blind,i hate family jobs lol

 

[macten]

Flooring grade chipboard, ply or tongue and groove floorboards.
Obviously the original floorboards need to be solid and deflection free first - this can sometimes be as simple as screwing into the joists (as most flooring is nailed), sometimes it is necessary to add extra noggins betwee the joists to shore it all up if you can't eliminate deflection. The Hardi screws are 30mm long and are designed for walls, I have spoke to Hardi and they will be rolling out shorter screws for floors soon. Since most wooden floor substrates are about 18mm thick then 30mm screws are too long to use in a bathroom unless you know where all the pipe runs are so you would be best to use 20mm turbo gold screws. I personally use NoMorePly screws and their mega strength adhesive to stick the boards down whether I am using NMP or Hardi 250.

 

[swanman]

Yes straight onto ply but glue down with fast flex and screw

No problem

 

[mz30]

Thanks guys jobs done ,ripped up old floor floor boards were probably the most solid floorboards i ever come across,put a load of screws in to the joist to be safe,used flexi adhesive plus additive (to be safe)to stick the boards then screwed down.

all seemed solid,tiles went down in no time.

Thanks for all the input again.