ᐅ Underfloor Heating in Older Homes with Adjacent Rooms of Different Floor Levels
Created on: 14 Jan 2026 22:55
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patrikwHello Nauer,
…so, I’ve switched over here now.
As far as I understood you, the leveling plan should be perfectly flat.
I would use 2cm XPS (extruded polystyrene foam) glued to the raw floor.
On top of that, a thin layer of leveling compound to ensure full-surface coverage.
Then, 2.5cm XPS boards on top.
The door-to-floor height is 7.5cm,
4.5 + 1.5 for tiles and adhesive = 6cm.
So, there is 1.5cm clearance left for a cover plate.
Has anyone ever tried a 2mm steel plate, 2000mm x 1000mm (6.6ft x 3.3ft), as a cover plate?
It should have better properties than a Fermacell board, right? (compressive strength, thermal conductivity)
No idea if tiles could be installed on that.
Thanks for the help and best regards
Patrik
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Hi Patrik,
the slope idea sounds good on paper at first, but in practice, you trip over it more easily than you’d think — even a 4cm (1.6 inches) slope over 12m (39ft) becomes noticeable, especially once furniture is in place and door gaps start to “shift.” I wouldn’t install underfloor heating plates on a slope; they need to lie flat, otherwise you’ll suffer quietly but steadily, usually only after a few heating cycles. Using insulation as a leveling layer is possible, but only if it is really compressive-resistant and doesn’t taper out like a wedge, otherwise the tile covering will slowly come loose, even if the adhesive looks fine initially. Nordic XPS without a cover plate is debatable — it’s technically allowed, but always feels borderline. I would at least consider a 10mm (0.4 inch) load distribution layer, even though it costs some height. The patio door is the real challenge here. Have you checked if it’s possible to gain 1cm (0.4 inch) clearance over the fitting, or is the door stop fixed? And how wide is the hallway actually — 1m (3.3ft) or closer to 1.4m (4.6ft)? It makes more of a visual difference than you’d expect. In the end, a clean step is often more honest than a sloped floor, even if it takes some getting used to; after all, we don’t live in a parking garage. Better to double-check your calculations now than to have to break out the screed later — that’s really frustrating, trust me.
…so, I’ve switched over here now.
As far as I understood you, the leveling plan should be perfectly flat.
I would use 2cm XPS (extruded polystyrene foam) glued to the raw floor.
On top of that, a thin layer of leveling compound to ensure full-surface coverage.
Then, 2.5cm XPS boards on top.
The door-to-floor height is 7.5cm,
4.5 + 1.5 for tiles and adhesive = 6cm.
So, there is 1.5cm clearance left for a cover plate.
Has anyone ever tried a 2mm steel plate, 2000mm x 1000mm (6.6ft x 3.3ft), as a cover plate?
It should have better properties than a Fermacell board, right? (compressive strength, thermal conductivity)
No idea if tiles could be installed on that.
Thanks for the help and best regards
Patrik
########################
Hi Patrik,
the slope idea sounds good on paper at first, but in practice, you trip over it more easily than you’d think — even a 4cm (1.6 inches) slope over 12m (39ft) becomes noticeable, especially once furniture is in place and door gaps start to “shift.” I wouldn’t install underfloor heating plates on a slope; they need to lie flat, otherwise you’ll suffer quietly but steadily, usually only after a few heating cycles. Using insulation as a leveling layer is possible, but only if it is really compressive-resistant and doesn’t taper out like a wedge, otherwise the tile covering will slowly come loose, even if the adhesive looks fine initially. Nordic XPS without a cover plate is debatable — it’s technically allowed, but always feels borderline. I would at least consider a 10mm (0.4 inch) load distribution layer, even though it costs some height. The patio door is the real challenge here. Have you checked if it’s possible to gain 1cm (0.4 inch) clearance over the fitting, or is the door stop fixed? And how wide is the hallway actually — 1m (3.3ft) or closer to 1.4m (4.6ft)? It makes more of a visual difference than you’d expect. In the end, a clean step is often more honest than a sloped floor, even if it takes some getting used to; after all, we don’t live in a parking garage. Better to double-check your calculations now than to have to break out the screed later — that’s really frustrating, trust me.
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