Large format stone on UFH timber suspended floor- a job for Ditra matting?

[Harry the tiler]

well its hard to judge without seeing a job in the flesh were as your tilers have seen it, however im with mudster i wouldnt lay stone on any chipboard floor unless its screwed solid to the joist and overlayed with 18mm ply or shower board and screwed at minium 200mm centres, im not keen on the matting stuff i wouldnt use it myself on any job, as above ask for a written guarantee but ill be suprised if they agree to it..

the thing is theres a differance between cant do and shouldnt do, on paper you shouldnt do it, you could do it and it may workout fine and you never have a problem or it may last for a few months then the problems start, the likes of myself and mudster wont do these jobs because its just not worth the risk that it will fail and then we are draged over the hot coles.

if i was the tiler i would be asking you for a writtern guarentee that should it fail i have no responsibilty for it...

Ok, thanks everyone for your help. I will ask the guy about a guarantee and see what he says, I suppose his response will at least give me an idea how confident he is. He's pretty enthusiastic about the matting, says he's used it a lot and thinks it will do the job. If he won't stand by it then I suppose I'll have to consider alternative flooring!

Thanks again,

Rob

[Mudster]

http://www.schluter.co.uk/produkt.as...a.xml&pg=infos

Take a look on this link and read the installation instructions with regard to plywood and particle board. It states clearly it must be anchored with screws to a suitable substrate.

Throughout the instructions it states that any substrate that must be covered has to be load bearing.

I don't like Ditra matting because it's used wrongly on a lot of installations in this country, it's designed as an uncoupling membrane to remove mechanical lateral stresses from flooring and therefore transfering these stresses into the tiled surface.

In laymans terms, large areas of substrate move over periods of time, even concrete slabs, that's why when you walk through Heathrow airport you'll find expansion joints in the flooring every 5 -10 metres.

Ditra matting is designed to provide a slip membrane allowing the concrete rafts to move independantly (on a microscopic level) from the floor covering thats fitted on top of the matting.

At no point is Ditra matting to be used as a reinforcement, it is not a replacement for reinforcement and should never be used as such. Any floor that requires reinforcement should be reinforced before Ditra matting is used.

This product has been in use for as long as I can remember, it is outstanding for the purpose for which it's designed, however it is not designed for laying on top of free floating floors of T&G partical board. Whatever specification your friends are giving you is wrong, feel free to direct them to the manufacturers site for a run down on what the specifications should be, if they aren't happy with that, point them in my direction and I'll put them right.

Many tile/stone suppliers in this country have very little experience of the actual mechanics of fitting, most are businessmen buying a product in and selling it on safe in the knowledge that they are not responsible for installation. The installer historically has been legally responsible to ensure any installation is correct.

This year this changed dramatically, the seller of the product is now equally repsonsible for making sure the product they sell is suitable for the use for which it is intended, the most common area in which this broken is the sale of 12mm Travertine for wall tiling, it's generally 50% overweight for plastered surfaces and borderline on stud walls.

Take my advice and that echoed of the other tilers on this forum, your friends are wrong.