Ditra, UFH, no more ply and Grooved board UFH

[Woodsta888]

Hi all,

I am after a bit of advice after becoming conbfised over many different answers from many different folk.

I have laid over a solid concrete floor battens which are fixed solidly to this floor. In between this there is celotex insulation. Fixed to these battens are grooved baords from Timoleon Underfloor Heating www.timoleon.co.uk/toronfloor-system-suspended.html. Over this I have boarded with 6mm No more ply and associated adhesive. The whole floor is 12m2 with 6m2 of UFH in a lower section of the kitchen. I have a 10mm gap all teh way round for the baords and the no more ply and the floor is solid. Maybe a touch small for ditra requirement but rather lay the ditra tahn rip out a Corian work surface and all the units if things went wrong with cracking etc.

I have now come to the point of laying the ditra 25 which I can do. I have glazed porc tiles that are 600x300 & 12mm thick and I'm confused as to what trowel and thickness to use. To lay the ditra the specs say 3-4mm notched trowel with tile adhesive and the tile bed not to exceed 10mm. Many tile outlets say use a larger 5-6mm notch to lay ditra and at least 10mm notched to lay the tiles. Schluter specs say use thin bed method but shops say use thick bed and back butter.

Very confused. Given the above what size trowels should I use for laying teh ditra and the tiles on top of the ditra relative to their size. And would you back butter and how thick.

I've tried to inform myself from many threads in here and become confused so may as well set my situation for comment.

Thanks in advance for any replies.

 

[Glynn]

The first thing is to follow the advice from Schluter. They made and tested the product. What you have with a Ditra matting is basically a solid bed of adhesive. When fixing the tiles I would use a 10mm round/square trowel and back butter the tile at 90 degrees to the floor adhesive, making sure that you twist the tile into the adhesive bed. Occasionally lift a tile to check you are getting good adhesive coverage. You need to make sure there are no voids under the tile has this could lead to low pressure building up and de-bonding the tiles.

 

[mike1979]

I use a 6 mm trowel for the ditra and use a 12 mm towel on the ditra back buttering the tiles

 

[DP Tiling]

Advice given by others is sound.

Ditra only requires 4mm, although many fixers I know use a 6mm.

The tiles on the other hand need a more substantial bed to ensure a firm mechanical bond with the Ditra. Back buttering the tiles is a good idea but also use the flat side of the trowel to fill the voids in the waffle of the Ditra too, as for adhesive manufacturer recommendations this refers to the finished depth of the bed so although using for example a 12mm trowel this will compress to probably 7 or 8 when the ribs are flattened and air pushed out so if you do opt for a 12mm you will still be fine.

 

[Rosco100]

Why are you using ditra over the no more ply ? Tile directly to the no more ply !

 

[SJPurdy]

Using more than 4mm ribs of adhesive under decoupling mats like ditra can mean that the adhesive is forced up through the fleece bottom layer and sets between the fleece and plastic which stops the decoupling working and invalidate any warrantees.

 

[lizzardtong]

4mm for ditra 25
6mm for ditra heat