ᐅ Electrician's chases – how to fill them?

Created on: 31 Dec 2015 10:28
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Ramona_91
Hello everyone,

We are building a KFW 55 house. Now a question has come up for us: Should the shafts installed by the electrician for the cables be filled with a special mortar (insulating or similar), or is it sufficient to use regular mortar?

Best regards,
Ramona_91
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Sebastian79
31 Dec 2015 14:02
Of course, you can use mortar; what would deform there – especially if a lime-cement plaster is applied afterwards.

If using gypsum plaster, then fill the gaps with that material, although only larger slots need to be prepared beforehand, the rest will be handled by the plasterer during the plastering process.
Mycraft31 Dec 2015 15:50
Sebastian79 schrieb:
what is supposed to deform there

The boxes will deform if you use cement/mortar because, unlike plaster, it shrinks significantly as it dries.

It’s only a matter of a few millimeters (inches), but that is enough to cause socket inserts to be misaligned afterward.
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Sebastian79
31 Dec 2015 15:51
I cannot confirm that... and everything was sealed with mortar.
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Peanuts74
8 Jan 2016 12:36
Regarding the initial question, for a new house the energy demand is calculated based on the insulation values of the walls, windows, etc. No one actually measures the real value afterward. So, it doesn’t matter at all for KfW.
In our case, the plasterer simply plastered everything, and so far everything is perfect...
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SirSydom
8 Jan 2016 13:10
Gypsum does not react well with cement!
So it depends on the type of plaster used.
Often, tile adhesive is used as well.