Some advice please re UFH in a large concrete screed poured in two parts.

[daveyates]

My first post here so apologies if it's not the right place to ask.
I've renovated a property and am finally, after 2 years, read yto put in the kitchen. The room is 10m x 4m and we are currently living on the concrete screed over wet UFH. The screed was poured in two parts due to the size of the room and there is therefore a crack running from wall to wall (so 4m long) about halfway down the room. The crack is no more than 2-3mm wide but I think it probably did expand/contract slightly when the UFH was running over last winter. There are no UFH pipes under where the kitchen units and island are going to go. We intend to put large (600 x 400) randomly coursed (ie not opus) limestone tiles down.
I have a few questions to which i have had different answers from BAL and from Schluter (not surprising I guess as they will obviously recommend their own product).

1) Do I need a decoupling membrane- if so which is the best?
2) Do I need a movement joint along the crack?
3) If I do need a movement joint does it need to be a preformed metal device or can I use something like an epoxy compound?
4) Do I need movement joints at the edges of the room? We intend to tile an upstand/skirt around the edge. The screed has a wooden 'former' around it so it doesn't quite touch the walls.
5) Anyone know a really good tiler in the York area?

As i say I've had Schluter telling me I need one of their movement joints and the Ditra matting, BAL telling me to put an Adshead Ratcliffe epoxypolysulphide compound in the crack and then use that for the movement joint as well and don't worry about the decoupling membrane. So I'm after a bit of impartial, expert advice please.
Many thanks in advance

Dave.

 

[grumpygrouter]

If it was me I would lay ditra and put in an expansion joint. Ditra will allow for a bit of movement and crack bridging but not a large gap. For expansion, why not use a silicone joint in place of grout at the movement area. You can get silicone the same colour as your grout from a number of manufacturers now.

 

[Ajax123]

There are lots of decouplers available as well as ditra from schluter. Dural, genesis systems, basf, nicobond all do them as well. Must have a joint reflected in the tile face a proprietary joint will last longer but look more obvious, a silicone type joint will look less conspicuous but won't be as durable. Re commission the underfloor heating if it has been off for a long time before tiling as well.If you put a joint over the screed break the uncoupling is not a necessity but is a belt and braces option. For the cost of it in comparison to the potential problems I would use it myself though.

 

[Time's Ran Out]

As per 2&3 above.
I would always recommend uncoupling for stone floors with UFH.
Yes to expansion joint at skirting.
Contact Dave at administration for a tiler local/available to travel to York or place a separate thread in Tiler wanted.