- Joined
- 15 Apr 2025
- Messages
- 4
- Reaction score
- 0
- Country
Hi there! I'm looking for advice on underfloor heating, or for people to tell me if the following is not a good idea.
I have a house from 1981, uninsulated concrete slab + bitumen painted DPM + 50–60mm screed. We want to retrofit UFH on the ground open plan floor (40 sq m) but the ceilings are very low (2330mm on average) so every mm counts.
So far I've been looking at 3 possible solutions:
1) Milling the floor (e.g. JK Floorheating) and tiling directly on top. Their heat output is high enough when spacing pipes at 125 mm centres, even with no insulation, and I can afford the downward heat losses. I would need to reroute couple of pipes that run buried in the screed, but nothing major.
2) 16mm EPS panels with embed ⌀12mm pipes at 120mm centres (e.g. Wunda Rapid Response) and tiling directly on top. Panels have a compressive strength of 400 kPA and it'd be slightly cheaper if I install the panels myself, as well as better insulated than option 1 (minimally, but better than nothing).
3) Digging out the 50mm screed until the DPM, repainting the DPM with rubber bitumen emulsion / adding sheet DPM, replacing with 50mm insulation (potentially bonded to the bitumen while it's still sticky), and then either a) routing the grooves for the pipes and tiling on top, or b) filling the height of the pipes with 20mm self-levelling compound.
I'm a bit worried of not having any or enough screed on option 3 - it seems that if every house has it surely it's needed - but if I understand correctly it's only there to level things out (which I could do with a very thin layer of self-levelling compound), or to add strength over the insulation layer (what'd be the minimum compressive strength required to be able to tile on top?). I'm aware that 50mm is not a lot to play with but I'm eager to make the most out of it.
I have a house from 1981, uninsulated concrete slab + bitumen painted DPM + 50–60mm screed. We want to retrofit UFH on the ground open plan floor (40 sq m) but the ceilings are very low (2330mm on average) so every mm counts.
So far I've been looking at 3 possible solutions:
1) Milling the floor (e.g. JK Floorheating) and tiling directly on top. Their heat output is high enough when spacing pipes at 125 mm centres, even with no insulation, and I can afford the downward heat losses. I would need to reroute couple of pipes that run buried in the screed, but nothing major.
2) 16mm EPS panels with embed ⌀12mm pipes at 120mm centres (e.g. Wunda Rapid Response) and tiling directly on top. Panels have a compressive strength of 400 kPA and it'd be slightly cheaper if I install the panels myself, as well as better insulated than option 1 (minimally, but better than nothing).
3) Digging out the 50mm screed until the DPM, repainting the DPM with rubber bitumen emulsion / adding sheet DPM, replacing with 50mm insulation (potentially bonded to the bitumen while it's still sticky), and then either a) routing the grooves for the pipes and tiling on top, or b) filling the height of the pipes with 20mm self-levelling compound.
I'm a bit worried of not having any or enough screed on option 3 - it seems that if every house has it surely it's needed - but if I understand correctly it's only there to level things out (which I could do with a very thin layer of self-levelling compound), or to add strength over the insulation layer (what'd be the minimum compressive strength required to be able to tile on top?). I'm aware that 50mm is not a lot to play with but I'm eager to make the most out of it.
Last edited:
