Fixing On Top Of Ditra Matting

[Old Mod]

So you mean you have 31/41mm to play with now?
Is that before any prep or does that include insulation boards?
Height build up would be like this.
20mm insulation
6mm heating and latex.
Choice between Ditra at 5/6mm or an antifracture mat at 2mm but for what you're asking Ditra would be better. (Bridging)
13/15mm adhesive and tile.
You do have options with transition.
If you go with expansion joint you don't need Ditra, antifracture will suffice.
The joint itself can be filled with this product.
Duran micro joint which can be colour matched to the grout.
Micro joints - Coloured Movement Joints - http://www.colouredmovementjoints.co.uk/movement-joints/movement-joint-types/micro-joints/

Or colour matched Silicon from grout company.
Not as good as above but would probably suffice.

Tilemaster & Bal are just two companies that provide 1mm antifracture mat.


*note!!
When you say concrete has been screeded, with what exactly?
A sand and cement screed (how thick?)
Or a latex levelling compound?

 

[ceekay]

31mm above plywood and 41mm above concrete/screed. This was purposely left 10mm below the ply so that we are able to use 20mm insulation boards on that area which will reduce to 10mm insulation boards as they come onto the ply area just strictly to try and get more insulation in so the heat goes up and not down. The plywood area has also got 100mm of insulation under the timber to try and achieve heat up and not downwards.

So therefore once all insulation is laid there will be around 17mm across the complete area which will need to incorporate a 10mm tile, 3mm of UFH and the adheshive so leaving around 4-7mm of adheshive to mount tile on but to include UFH.

As the insulation boards will span the end of the ply and the beginning of the concrete/screed was hoping this would be a sufficient bride? The ply is fixed extremely well in and around the edge of the board but obviously thus doesn't nesscessarily stop expansion and contraction but we will also be stopping the tile slightly short of the perimeter as skirts will be fixed afterwards.

The screed type I'm not completely sure of but could ask them. It was laid to bring the concrete up Level as it dipped off around 15mm in the odd area so was a wet screed with the first layer was containing loads of tiny stones. The company who load it said it is find to tile on within a few days.

So that's my dilemma if to use a decoupling mat and if I could fit it in? I believe Bal do one less than 1 mm but not sure if it's as good as Ditra's 3mm version?

Many thanks, keith

 

[Old Mod]

Well the UFH should have a latex covering, for a few reasons.
One it provides protection for the heating cables.
Two, it achieves a better transfer of heat between cables and tile.
Three, eliminates the risk of air pockets beneath the tiles, which can cause the cable to overheat and burn out.
Yes it can be bedded in adhesive, but you must employ a fixer who, Is not only willing to take it on, but is also competent enough to do the job without damaging the cable and who can guarantee laying your tiles in to a completely solid bed.
17mm was really too tight to be able to safeguard as well as you could of, in my opinion anyway.

 

[ceekay]

Thanks for the advice 3fall
Do you thinks it's still viable in the heights to use latex? If so what would you recommend?
What about the less than 1mm bal decoupler ? Any good ? Viable in the height?

 

[Old Mod]

without actually seeing it myself, I wouldn't like to say anything for sure.
You know, it's going to be a call your fitter really needs to make.
It'll depend how good he is tbh.
I wouldn't enjoy working to such a height restriction, but maybe it would be possible.
but your floor needs to be perfectly flat to start with, otherwise it'll cause all sorts of issues over such a large area.
To expect to fully bed a tile and incorporate UFH of 3mm inside of 7mm, I feel is a tough job.
And I don't think you could squeeze a mat in to those dimensions either.
There would have to be a compromise in my opinion.
To incorporate a mat comfortably, I would suggest a reduction in insulation boards on the ply to 6mm, giving you the extra clearance you require. Obviously on the screed side too. I know this would be less efficient, but you could incorporate more protection for your heating and floor.
Or just go with your plan. 6 of one and half a dozen of the other really.
But this is just my opinion, others will certainly have theirs.
I'm sorry I don't feel I can give a definitive answer without seeing the project.

 

[ceekay]

Thanks again 3fall
Was my thinking as I read to reduce insulation boards in that are to 6mm especially since I will have 100mm of Celotex under the ply area. Oh they are 25mm ply by the way. Problem with that is we would need to reduce the 20mm insulation boards as well and reducing by 4mm out of the 20 would leave us at 16mm requirement which We cannot get. I suppose I could get 10mm insulation fir that part and increase the beds?
Much appreciated I will see what he says by I'm usually the King of overkill where possible.

 

[Old Mod]

10+6=16 😀