Hi everyone - I'm new on here so wanted to say hello...and to ask some pretty basic questions about carpets and UFH. I want to use electric heating mats in a lower ground floor bedroom, solid concrete slab, wool carpet with apx. 1.4 tog value. The slab is as old as the house (ie ancient) so will be sealing this with a liquid DPM before anything else happens. Firstly, what is the best sort of insulation to lay on top of the slab but underneath the mats? I would prefer something thin and flexible since the floor isn't perfectly level. Secondly, what needs to happen once I have put the UFH mats down? Most of the ones I have seen tell you to lay 10mm of self level compound, while others (e.g. Rayotec) claim that you can put carpet / underlay straight on top. I would rather avoid putting down self level for reasons of mess / floor height buildup. Do you really need it? Could you feel the UFH mats through the carpet, or it more about even heat conductivity? Any help greatly appreciated, thanks!
I would be very reluctant to put carpet (even with underly) straight on top of these heating mats. I have seen to many telephone and speaker cables frayed. I would be afraid of an electrical short at some time in the future.
From a fire service point of view, I'm inclined to wholly agree with Hobbit. Over time the mats will break down in areas of foot traffic, in turn possibly exposing open cabling. Carpet with a good underlay wouldn't call for UFH I wouldn't of thought?
Firstly, I think it would be a potential fire hazard directly under carpet with no hard barrier between the mat and the carpet. Underfloor heating systems are really designed to work under hard flooring. Wet systems are encased in concrete or under ply or similar, and again with the mat systems I have seen they have a ply or other hard flooring laid over them. Secondly, I can't believe you will get the true benefit of UFH with carpet. The carpet will act as insulation preventing the heat transferring into the room, and unlike hard flooring the heat will not radiate evenly throughout the flooring surface(carpet), you will simply get hot/warm spots under your carpet. E.G. Placing a rug on a wooden floor will usually damage the flooring. The rug acts as an insulator preventing heat transference causing the wood to get too hot causing damage to the flooring. Carpet and UFH don't really work well together This is my opinion, I am not quoting the results of a scientific test, but I suspect that if you ask the manufacturer (not the supplier) of the UFH system for their views on this I would be very surprised if they agree with using their system directly under a carpet and further more I would be amazed if they agree to put it in writing.
If you want underfloor heating then have a nice Lvt on top. if you still want carpet then spend what you would have had to spend on the ufh and get a good quality underlay and a nice deep pile carpet!
I have visited the rayotec website and they do indeed say that you can use their mats under carpet. But there a a few things I should point out. You must use a 6mm insulation layer first on to the subfloor then underlay and then carpet. The underlay must be no more that 0.8 tog and the carpet max 1.7 tog.. You CANNOT put any heavy furniture on the heating mats. A couple of observations.... The gripper rods will need to be packed up by 6 mm + 2mm . you are limited to your choice of carpet and underlay combo.. And you can only put the mats in the "free" areas ie walkways only, you can't ever rearrange your furniture or even move you suite about. I feel this very impractal as to make it unworkable. You would need be careful when buying any new furnishings and inform any buyers if you were ever to sell the house. I would still be concerned about cables fraying although the sandwich between soft layers should help
