Underfloor heating

[FamilyWiggs]

Finally getting round to laying the floors in my project.

I'm relaying the Heather Browns in to the dining room, and putting slate flags in the sitting room. 60 sqm in total. I'm laying electric underfloor heating mat under both. As SWMBO would prefer to spend a small fortune on her klingstrip habit than on ridiculously expensive flexible tile adhesive, I was thinking of laying them in a screed of sand/lime/cement in a 6:2:1 ratio. Given the flags are of varying thickness, adhesive rally isn't a viable option.

Any thoughts on this? Will the lime make the screed "soft" enough to have similar flexibility to the adhesive?

 

[sue gazzard]

Hi, the critical thing is that the screed is flexible - it will be disastrous otherwise. Also my experience with electric ufh is that the time spent laying cable is really worth it as you can get exactly the right amount of heat exactly where you want it by varying the distance between lines of cable, or not putting down cable at all (for instance under a divan bed where it can make for an uncomfortably hot sleeping environment). Otherwise it is utterly brilliant!

 

[FamilyWiggs]

Thanks Sue.

The other thing I am wondering is whether the lime or cement will attack the plastic sheathing of the cable?

 

[DaveBrigg]

I hope that lime doesn't attack plastic, as much of our wiring and push-fit plumbing has been directly plastered over. The various professionals involved did not raise any concerns, although the gas man insisted that the copper gas pipe be wrapped in insulating tape where it ran inside the wall.

 

[Gervase]

Plastic isn't affected by lime, although it's a good idea to put the cables under plastic caps or trunking as this will allow the electrician some 'wriggle room' when he comes to do the final fix, without the risk of the plaster popping near sockets where the cables have been pulled or twisted.