Help please - conflicting opinions on tiling on chipboard - TilersForums.com

[GrahamC]

HI - I'm new to this forum and new to floor tiling.

I am refurbishing my old bungalow - it has suspended floors with 100x50mm joists at 400mm centres, supported on brick sleepers running full width of the room (at approx 1000mm spacing along the joists) with 100x100mm wooden sleepers on these which the joists are nailed to. I have put 100mm celotex insulation between the joists, there is still a 300mm air gap under this for air circulation via air bricks for venting.
I am where I am: flooring on top is W/P (green) T&G 22mm chipboard screwed into the joists with Turbogold 60mm screws at 150mm spacing - all joints have been glued with waterproof PVA. The area is 2 rooms, each approx 3x4m which lead into each other (wall taken down). There is no discernible vertical movement between boards, I do not have UFH, just normal radiators for C/H. 20mm gap between edge of c/board and all walls

I want to tile it with travertine natural stone 12mm thick, random pattern - this is my problem, I have had 3 different opinions how best to do it - all conflicting apart from all advising flexible adhesive and grout at all stages and a movement expansion joint between the rooms

1) prime chipboard then tile away with a good 2 part flexible adhesive eg. Ardex, stonefix or equivalent
2) prime as above, DITRA matting (on flexible adhesive) to decouple the tiles, then tile on that with flexible adhesive - but I undestand this is only good for lateral movement but not vertical movement.
3) 6mm Hardibacker board stuck & screwed to C/board, then tile on this again with flexible adhesive, but if there is any movement then surely this hasn't decoupled the floor and the problem of potential cracking remains.

I think you can see my problem and there is quite a cost variation,
thanks in anticipation of your help - Graham

 

[tfs]

In my opinion I think using the dittra mating sounds like the best bet.

You mentioned that you thought this may no tbe too good for vertical movement in the floor. I feel the best way to eliminate bounce in a floating floor is firstly in the construction of the floating floor. After this you could always board over in an attempt to make more solid and further attempt to eliminate any bounce. From here I think the rest needs to be left to the flexible adhesive.

Floating floors and chipboard etc are always at highher risk of movement, cracking etc. You can only reealy prep as much as possible hence my opinion that dittra matting would be best and you could incorporate a 15mm ply under the dittra as an extra.

ask your tiler if he has contacted the ditra matting manufacturer for guidance or visit there website yourself and contact someone in there technical dept.

www.schluter.co.uk

keep us updated mate

 

[grumpygrouter]

You don't say how big the area is to be tiled. This can have an effect on the most cost effective way of dealing with this. Ditra is cheaper to buy in 30m rolls, bringing the price down to around £8.50 m2. I would be happy to use this if the floor is absolutley solid with no vertical movement. It would give the stone a much easier time.

Hardiebacker 6mm is again an alternative but it doesn't strengthen the floor much. Per m2 this works out about £14.58 so is more expensive than ditra. Ply would probably work out the cheapest covering if you needed it but you will have height issues. Even with a solid floor (non bouncy), I wouldn't use less than 9mm ply.

 

[GrahamC]

Thanks to both of you - the more I have been reading the more I'm sure you are right - I've decided to go for the Ditra Matting with BAL Rapidset flexible to secure the Ditra to the C/Board and then the Travertine stone tiles to the Ditra - unless you would specifically recommend an alternative adhesive.

I know its not the cheapest route, but I'd rather spend the extra and get it right - after all the tiles aren't cheap!

Finally, I'm estimating a 20kg bag should cover approx 4sq m, on the basis that I'll be using it to stick down the Ditra to the C/board as well as for the tiling - is this reasonable - or do you feel I'm over or under estimating ?

Total area (the 2 rooms) approx 24 sq m, so estimate 6 bags.

Finally: Boyden tiles in Surrey are doing Ditra @ £5.95 (+ vat) sq m for 30m roll! - not bad !

Thanks Graham

ps:I would have sent you each an individual "thankyou" - but I'm completely new to forums - this is the first I have ever joined & I can't work out how to do it.

 

[grumpygrouter]

Hi Graham, thanks for your input. To thank an individual, you simply go to the post that contains the info you want to thank them for and click the "Thank" box on the bottom right of the post.

As for your ditra/adhesive question, you need to bear in mind with Ditra that there are cavities to fill in the mat and it will take additional adhesive for that. Obviously the adhesive you use to stick the matting down is only a small notch trowel. I would certainly look at having at least a couple of bags extra to be on the safe side. Make sure you can return them if you don't use them.

Also, just to clarify, Ditra DOES NOT eliminate vertical movement so you base floor must be solid. Best of luck. lets us know how you get on.