Hi there, I have a problem that I keep on going over in my head and keep comig to different conclusions!

Went to have a look at a job and it is around 50sqm in slate 900x600, basically one big room. It is weyroc on joists and it has been glued and screwed with no deflection visable.

Now here is the problem, there are already some built in wardrobes and units and the joiner has only left in the region of 25-28mm (only quickly measured) under the doors that open. Therefore the tiles must come in uder that.

I recommended to him to overboard with 12mm ply then lay the electric ufh, mapei fibreplan then tile. I worked on 12mm+5mmslc +4mm addy and 10mm tile. Making 31mm and this is too much.

So i thought 6mm hardi but i don't think this is an option because of cost over the 50sqm.

I'm now thinking along the lines of not using the slc and tiling straight on to the ufh. theerefore saving some height. Suggested by local tile shop, but worry abot this creating future issues.

Also thought about using ditra in some way to isolate from the chipboard(very solid).

Whats the best option to come in under 28mm and keep cost resonable
Any thoughts welcomed

the 6mm hardie is the best route imo James, and SLC over heat mat, which local tile shop suggested no slc? was it Chris at W'mere Tiles?

is the slate calibrated or random thickness?

Don't think Ditra is suitable on Chipboard. Could the wardrobe doors not be adjusted by 5mm.

I don't know if it would be suitable and it might sound a bit off the wall - excuse the pun - but could you screw a sheet of 9mm plasterboard down to the weyroc and tile onto that.

Alternatively you could look at a gypsum based levellling compound rather than a cement based one. As with gypsum based screeds they can be laid thinner thant their cement equivalents and are much more flexible so might give you enough depth reduction.

I am not a tiler so not sure and so invite comments from the pro's on here.

Originally Posted by Ajax123

Don't think Ditra is suitable on Chipboard. Could the wardrobe doors not be adjusted by 5mm.

I don't know if it would be suitable and it might sound a bit off the wall - excuse the pun - but could you screw a sheet of 9mm plasterboard down to the weyroc and tile onto that.

Alternatively you could look at a gypsum based levellling compound rather than a cement based one. As with gypsum based screeds they can be laid thinner thant their cement equivalents and are much more flexible so might give you enough depth reduction.

I am not a tiler so not sure and so invite comments from the pro's on here.

plasterboard no good on floors Ajax, moisture issues, and altho it would probably have the compressive strength, I doubt it would have the tensile strength. First time that I've ever heard it suggested tho;

Originally Posted by doug boardley

plasterboard no good on floors Ajax, moisture issues, and altho it would probably have the compressive strength, I doubt it would have the tensile strength. First time that I've ever heard it suggested tho;

Cheers doug - Ever the maverick me. Just cos it has never been done don't mean it can't be done in my book. I have seen plasterboard used on top of wooden floors as a sound deadening layer and then Floating Laminate flooring on top of it. Not aware of any problems. Obviously appreciate laminate and tiles are different things. In this instance the client had wanted to use a Gypsum Screed on the wooden floor but did not have the required depth (35mm) so decided to use plasterboard instead. Not a normal use I know but seemed to work in that instance. If there is no deflection in the subfloor I don't think the flexural strength would be an issue would it?? Have to say I don't actually know what the compressive strength of plasterboard is.....

Cheers for the replys, no Doug it was World of Stone not sure who it was though, Richard was out at the time. Its calibrated slate. Any ideas where is the best price on hardi round here?
Not sure the customer is going to stretch to hardi and i'm afraid that if I insist he will just us someone who will just do it no questions asked, he said that another local tiler had looked at it said it would be fine with 4mm ply So i think he thinks i'm well over egging it...

If they're gonna be prepared to not do the research and just go for cheapo quotes then I'd be more than prepared to walk away from it. 50m2 of callibrated slate deserves to be laid with the best possible chance of surviving imo World of Stone don't really know their backside from their elbow really as far as tile installs are concerned, altho the blonde girl, is she a Kiwi?, always gets on to Mapei tech dept if you have a query

You also need to consider the additional weight that 50m2 of slate is going to put on the joists. Straight onto chipboard is asking for trouble imo. Really think the floor will need a bit more strength for a ton and a half of slate to go on it!!

I agree with Grumpy floor seems fine at the moment but when you have put all that extra weight on it there will be some movement and this could give problems down the line

thats a good one plasterboard on floors im with doug on this one