Fixing On Top Of Ditra Matting

[ceekay]

Hi chaps
I know is an older topic now but I will be having tiles fitted soon over concrete and timber. The concrete is being levelled slightly then 20mm warm up insulation boards being placed over it and the timber part is 25mm wbp ply and us having warm up 10mm insulation boards fitted which will pretty much level up the two different substrates. I am then installing warm up ufh mats (3mm) and the tile 9.5-10mm it has just been suggested to me that I should be using the ditra 25 mat as well to help prevent any damage afterwards from the two different floors expanding and contracting. Is this a recommended way to go? Wouldn't want cracked tiles at the transition point one complete? Any advice please and if recommended does the warm up mat sit in top of the ditra or below?

 

[One Day]

Hi chaps
I know is an older topic now but I will be having tiles fitted soon over concrete and timber. The concrete is being levelled slightly then 20mm warm up insulation boards being placed over it and the timber part is 25mm wbp ply and us having warm up 10mm insulation boards fitted which will pretty much level up the two different substrates. I am then installing warm up ufh mats (3mm) and the tile 9.5-10mm it has just been suggested to me that I should be using the ditra 25 mat as well to help prevent any damage afterwards from the two different floors expanding and contracting. Is this a recommended way to go? Wouldn't want cracked tiles at the transition point one complete? Any advice please and if recommended does the warm up mat sit in top of the ditra or below?

Hi. Warmup mats go below the Ditra, cover with slc first though. As for the bridge between the two floors, ditra will go a very long way to absorbing the lateral movement but it's more vertical movement which will present the biggest risk. That's why Schluter will say the same as i will: you should install a fixed movement joint, such as dilex, on the joint and follow that through the ditra and to the tiles. Can look ok if planned properly.

 

[ceekay]

Hi. Warmup mats go below the Ditra, cover with slc first though. As for the bridge between the two floors, ditra will go a very long way to absorbing the lateral movement but it's more vertical movement which will present the biggest risk. That's why Schluter will say the same as i will: you should install a fixed movement joint, such as dilex, on the joint and follow that through the ditra and to the tiles. Can look ok if planned properly.

Thanks Impish
Not had any advice of my tiler in ref to the transition between the ply and the concrete. Told him I'm planning on using 20mm insulation boards on top of the levelled concrete and 10mm insulation boards on the ply but the 10mm boards would bridge and stagger across the different substrates adhered with tile adhesive and have asked him to lay these for me. Then warm up heat mats in the tile adhesive above then the tile. It was mainly my plasterer that has suggested I use the ditra 25 mat as well but ditra have said they would put slc over there mat? I only have 30mm over the ply and thus is to include the tile and insulation board. Very confused now and the work starts in a few days. Any advice from anyone greatly appreciated.

 

[jobdone]

If your tight for height. You could look at variopro ufh decouplingand heating in one. Ask Lee at tile town

 

[ceekay]

Thanks Jobdone but unfortunately already purchased 51sq mtrs of warmup mats. Got around 31mm on top of the ply but have 41mm over the concrete now it's been screeded.

 

[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