What is the ideal substrate floor for tiling on?

[samnjarv]

Hi to everyone using this forum, My name is wayne and i'm a newbie and in need of some advice..
My bathroom is 1.8 by 2.9. The joist's are 7"x2" and these run the 2.9 lenght, the joist's are spaced at 17" centres and the old floor boards layed at present are about 22mm thick. I am about to rip the whole of the bathroom out which also includes lifting the old floor back to the joist.
My question is how do a achieve a perfect substrate floor ready for the tilers. Do i just simply replace with 25mm WBP ply? or would i be better going down to an 18mm WBP ply, then lay 6mm no more ply over the top so theres better protection for the ply and a better suface for the tiler to tile on.. think i would have a lip if i went for the 25mm ply and 6mm no more ply on top.

 

[AliGage]

18mm ply is the minimum. Id then overboard like you say with a tile backer or cement board. For timber floors id usually use hardie.

What has your tiler said? If i was tiling it id prefer to do my own prep. But at the very least id insist on doing the backer fixing. Id be able to check the ply fitting if you get what im saying 😉

 

[samnjarv]

Hi aligage one tiler mentioned just using 25mm ply.. I love to use both 25mm plus a tile backer board but the height would be to much. i just dont know what to do for the best, would tiling on the wbp ply be good enough or will i get problems yrs down the road

 

[AliGage]

18mm screwed to joists will be fine. Add extra noggins especially where there are joins in the ply. Then glue and screw hardiebacker over the top.

Ply in my opinion is flawed from the offset to tile straight onto. It can delaminate, move in varying temperatures, warp, is terrible if it gets wet and it rots. But it's better than chipboard 😉

 

[samnjarv]

Would 18mm wbp ply be ok to use then as long as i'm using no more ply on top? also if i'm using no more ply on top would i still have to wbp ply or could i just use a normal ply board and seal it with sbr?

 

[Gazzer]

Yes as long as the floor is solid with no deflection....that means NO DEFLECTION, not some deflection. While you have the floor up strengthen the joists.

 

[samnjarv]

How do I do that? Just by placing noggings between them? Could I use a normal ply about 22mm instead of 18mm wbp and just seal it before laying no more ply down.

 

[samnjarv]

Is deflection the joist movement up and down or joists moving away from side to side?

 

[Gazzer]

up and down. They should be firmly fixed though, I guess once the ply is screwed to the joists it will all be as one anyway but IMO best to sort them out first.

 

[samnjarv]

If there is slight movement how do you remedy this? Also if i'm going be using a backer board on top of the ply, does the ply still need to be wbp?

 

[samnjarv]

Is it a good thing to glue the ply to the joists? If so whats the best stuff to use and where to get it from? Could I use no nails

 

[Gazzer]

you could lamintae the joists using 18mm ply glued and screwed either side of each joist , This added good strength it also lets you level floors up too.

 

[samnjarv]

Am I better using a wbp ply even though I'm going over it with nmp backer board. What type of screws will I need to use and where will I get theses from.