New bathroom installation - Floor question

[richardlee]

Hello Guys.

I have just removed my bathroom flooring, back to bare joists. The room is 8'x6' and I will be laying 16" square travertine tiles.

I have read through the posts and spoken to a few people on what to fit as a base, it's all going to be new, wastes etc so floor height isn't really an issue but the lower the better.

I was thinking of the following:
18mm ply screwed to the joists with zinc screws and tanked, then tiling directly onto this. I thought that the ply would provide the rigidity whilst the tanking would prevent moisture ingress into the ply. Is this a good way to go?

I have seen recommendations on using tile backer but from what I have read, tile backer is good when battened to a wall as is does not fail when saturated but on top of ply it seems that it would simply be providing a good tiling surface, but I would still need the ply for rigidity, so the tanked ply would be good enough anyway. . . ?

I have also read that some just tile directly to marine ply, any thoughts on this?

Thanks guys.

Richard.

 

[charlie1]

I would be inclined to use a decoupler such as ditra aswel, this will both prevent any moisture ingress and isolate any expansion in the timber. If you dont use a decoupler then you risk your timber floor tearing your tiles appart. Also, add extra noggins between the joists. Cement backer board will eliminate deflection in your floor and everyone would advise you use this on top of your plywood

Ideally, 18mm ply, then 6mm backerboard glued and screwd then ditra then you can tile

Good luck.

 

[richardlee]

Cheers charlie1.

So you recommend 18mm ply, tanking then decoupler?

Thanks.

 

[Stewart]

Install 18mm ply with extra noggins for support and to make as deflection free as possible. Make sure you prime the back of the ply and the edges. I would then be inclined to install 6mm cement backer boards glued and screwed, then tile.

 

[richardlee]

Thanks Stewart.
What is the best product to use to prime the exposed ply and what would you use to glue the cement board to the ply? Also, is there a preference to the type of cement board used; Marmox, Aquapanel etc?
Your advise is appreciated!

 

[Stewart]

I use Weber AD250 for priming the back and edges of Ply. I use Weber SPF for sticking the NO More Ply down. I then screw it down at 200mm centres. If using No More Ply, you need to prime the front and back of the boards too. This is the method I use when there is no underfloor heating involved.

 

[richardlee]

Thanks Stewart. I put the ply down today and its nice and solid. I am thinking of putting down electric underfloor heating. Would I use something like ditra for this and leave out the hardi backer?

 

[Hardie.Guy]

Richard you can use Hardiebacker 6mm Cement Backerboard with the underfloor heating. It should always be placed between the structural timber floor and the heating element. Never place heating under Hardiebacker as there is a risk of damaging the system when fixing down the backerboard with nails or screws.

Hardie Guy

 

[nybor62]

if your having ufh go with the 18mm ply then insulation boards glued and screwed then ufh then slc over the ufh then tile imo

 

[richardlee]

Thanks guys.
One quick question. Are cement boards the same as insulation boards?

 

[Mike]

Thanks guys.
One quick question. Are cement boards the same as insulation boards?

Cement boards have some insulation properties but not as good as insulation boards.

tapatalk on my HTC

 

[Hardie.Guy]

Hardiebacker Cement Board for tile and stone is to be used to have a water resistant proper surface to tile upon. It has very little insulation properties.Hardiebacker would heat up quicker and transfer heat better than wood as it has a higher thermal conductivity value, woods acts more as an insulator.

Hardie Guy