ᐅ Expanded polystyrene (EPS) granules for varying structural floor slab heights

Created on: 4 Mar 2021 10:34
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Eyko123
Hello,
we are currently planning the ground floor floor construction in a single-family house that is being renovated. The house is only partially basemented, and the structural height in the basemented rooms is higher than in the non-basemented rooms. If we now install expanded polystyrene granulate (then underfloor heating and screed), there will be 12cm (5 inches) of granulate in the basemented rooms and 28cm (11 inches) in the non-basemented rooms. Can anyone tell me if this might cause problems because the granulate could settle unevenly over the years? Would it be an alternative to raise the non-basemented rooms with expanded polystyrene granulate to the same level as the other rooms and then install insulation boards everywhere?
Thank you! 🙂
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Eyko123
4 Mar 2021 14:54
Thank you all for the responses! 🙂
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pagoni2020
4 Mar 2021 18:39
You probably mean perlite? That’s what I would consider, rather than polystyrene granules.
A carpenter once told me that to even out small irregularities, he first lays down 2-4cm (1-1.5 inches) thick polystyrene boards, which absorb minor bumps and unevenness. Then he installs his beam structure or other subfloor construction on top of that. Using a loose fill material followed by panels sounds like a sensible approach to me.
Maybe you have some photos to help visualize it better? I’ve seen mentions of 28cm (11 inches) height, which would allow for a decent amount of insulation. 🤨 🤨
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Eyko123
5 Mar 2021 10:02
Here is a picture showing the transition from a basemented area (high floor level) to a non-basemented area. We can still remove the smaller uneven spots. The screeding company always refers to expanded polystyrene granules with a thermal conductivity of 0.043 W/mK.

Rohbau-Flur mit offenen Wänden, losen Kabeln, Baugeräten und unebenem Betonboden


Unter Renovierung: heller, leerer Innenraum mit abblätternder Wandfarbe, Durchgang, Besen am Boden.
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icandoit
5 Mar 2021 10:07
Different settlements are to be expected. In the area of the transitions, make sure to place a mat in the screed, otherwise cracks will appear over time.

Alternatively, provide a joint in the area of the transitions.

Insulation is not the only important factor. For example, I would recommend anhydrite screed because it has high bending and tensile strength. Additionally, it requires a shorter drying time.
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Eyko123
5 Mar 2021 10:29
What kind of mat would that be? Would it then be placed, for example, at half the height of a 7cm (3 inch) screed thickness?
Good point about the anhydrite, thanks.
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pagoni2020
5 Mar 2021 10:36
A silly question. I can't quite see from the pictures how it continues next door.
Couldn’t you remove that raised area completely so that both are on the lower level?
It looks in the picture as if there are hollow bricks or something similar on the floor...