upstairs toilet floor preparation for Travertine tiling ?

[pzzszk]

I am looking for advice on whether I need to put down either an overboard (tilebaker, wedi, hardie, ply, etc); a decoupling matt (Ditra, etc) or neither......

The details are:
The room is a small upstairs toilet (i.e. not a wetroom nor a bathroom)
Travertine honed & filled 405x405x13mm tiles (only 12 tiles required for floor)
Floor is 1.1 m2 (0.850m x 1.3m) made of floor board planks (18mm x 140mm) - not T&G
There are 3 joists running down the length of the floor which are 2" x 12" on 300 mm (12") centres
Floorboards are screwed down at each joist (@ 300mm)

Taking the floor boards out & re-flooring is not an option, due to the construction method of the inner wall.

As I am raising the floor level by 13mm already (10mm plus adhesive), I am looking for the smallest additional increase in height. And because the area is small, cost is not an issue.

Would a 6mm wedi board be sufficient? Would just a de-coupler be OK?

There doesn't appear to be any movement in the floor and it all looks solid......However.....

From all my experience (limited) and everything I've read - it seems to be a high risk strategy to put nothing down.

So, recommendations please....

Thanks.

[Rich]

Hello and welcome to the forum. You have done the right thing coming on here and seeking advice BEFORE you start, to many people get that wrong.

I have attached a link to a post i put up some time ago regarding wooden floors, have a read through as it might give a little bit more info.

You must not tile directly onto the floor boards, you will need lay something first. IMO the best way of doing it to get the best possible floor to tile onto would be to remove the floor boards, replace with min 15mm ply, screwed down at a min of every 300mm and then over board with a tile backer board, screwed and glued. If however the floor boards are in good nick (not water damaged at all) and are well and truly fixed to the joists with no deflection, then you could just over board with a tile backer board (glued and screwed).


I myself would not be to comfortable just using Ditra over floor boards but others may disagree but I would feel much better laying it over ply/backer board.

Plywood floors...

[Gall.B]

With Rich top advice as always

Going on top of the boards with a decoupler is not an option I would consider.

15mm ply primed all sides and covered in screws then a decoupler if lifting the boards is not possible, leave a gap around the perimeter for expansion when laying the ply fill with silicone.

Good quality white addhesive needed backskim tiles to fill any pits before fixing to a serated bed (12mm notched trowel)

Any pics of the floor in question?

[pzzszk]

Rich & Gall.B - thanks...very useful information.

Sounds like "doing nothing" is a bad idea.. And that using just a de-coupler on top of the floor boards is a bad idea.

That leaves me with overboarding....

I seem to have 2 choices for overboarding:
15mm ply
??mm tile backer board

Would a 6mm tile backer board work?

Upstairs loo floor.jpg

The tiles at the back are laying loose just for viewing/orienting. The main joist runs down the centre and the others are 12" to the left & right. No movement in the floor at all.

[Rich]

How thick are the floor boards? 22mm? Is there no way you could remove the floor boards, cutting them off at the walls? Then replace with 15mm ply? Then a 6mm backer board?

This would give you about as good a substrate to tile onto as you could ever hope for.

[Rich]

If you absolutely can not replace the floor boards then I would screw them to death! Get rid of any bounce or squeaks and then over board with a backer board.
As for the height difference there are loads of door strips on the market that will hide the height difference.

[steve187]

The problem I can see with cutting the boards off at the walls, is that neither the boards going into the ajoining rooms, or the ply in the toilet, would be supported at the edges, unless some extra joists could be installed, the original floor boards looks as if they have been up a few times, and I can not see them being a good base for a backer board, I think that you will have to overboard with 15mm ply and then backer board, but that would give you a 36mm step into the toilet area. But that could be feathered in with a wooden door bar, the width of the door casing. not an ideal solution.

And i almost forgot welcome to the forum.

[pzzszk]

steve187 - you're correct, the wall is sitting on the boards between 2 joists (one in the toilet & one in the room next door). And there is no access for putting in new joists. So, as you say, replacing the existing ones is not an option.

They have been up a few times...but as Rich says "I can screw them to death". I have already done this and there is no squeak nor bounce in anything. A glass of water doesn't ripple when I jump up & down. And I'm 14 stone.

Do you think that Rich's suggestion of "screwing them to death" and overboarding with a 6mm backer board will work?

[kilty55]

a 6mm cement board in your situation will be fine imo

[Rich]

To be honest, if you cant replace the floor boards then you have little choice. If the floor is defection free then a backer board should be fine.

[steve187]

I think thats its the only way to go, and i agree with Rich, its a small area so its the best solution

[pzzszk]

Thanks to all for the advice & guidance. Much appreciated.