From shell construction dimension to clear room height

Hello Forum,

this topic has been partially addressed in some posts, but it has not yet brought me the final enlightenment, so here is the question again in my own words:


How do you correctly calculate from the raw construction dimension to the clear room height?


Raw construction dimension:
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The construction standard dimension is 12.5 cm = 1/2 brick layer, so 1 brick layer in the shell construction is 25.0 cm.

Accordingly, the raw construction dimension is
- for a current "standard" living room height 10.5 layers = 262.5 cm
- for a current basement room height 10.0 layers = 250.0 cm


Clear room height:
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The clear room height = raw construction dimension - ceiling - floor

Ceiling:
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The ceiling = raw ceiling + ceiling plaster + ceiling cladding (e.g. wooden ceiling)

From what I have read so far one can roughly assume:
Raw ceiling = 20.0 cm (concrete ceiling)
Ceiling plaster = 1.5 cm
Ceiling cladding = 3.0 cm
That means
- in living rooms one needs 21.5 to 24.5 cm for the ceiling
- in basements the ceiling is usually left untreated (20 cm).

But what if a central ventilation system is installed in the house?
The necessary pipes in new construction are installed in the ceiling, which makes sense. From what I have read so far, spiral ducts are the cleanest solution but have a diameter of 16.0 cm.

1. Then, to ensure stability, does the raw ceiling become correspondingly thicker: instead of 20.0 cm then 36.0 cm?


Floor:
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For the floor it depends on whether with or without underfloor heating:

* Floor without underfloor heating:
Floor = screed + impact sound insulation + floor covering

From what I have read so far one can roughly assume:
Screed: 5.5 cm
Impact sound insulation = 2.5 cm
Floor covering = 3.0 cm
That means
- in living rooms the floor has 11.0 cm
- in basements no impact sound insulation is needed, so 8.5 cm remain

* Floor with underfloor heating:
To the floor without underfloor heating adds the insulation layer with the pipes for the underfloor heating = +6.0 cm
That means
- in living rooms the floor has 17.0 cm
- in basements no impact sound insulation is needed, so 14.5 cm remain


The clear room height would then be
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* without underfloor heating and without central ventilation system:
raw construction height (living room) = 262.5 cm
- ceiling = 24.5 cm
- floor = 11.0 cm
= clear room height = 227.0 cm

* with underfloor heating and with central ventilation system:
raw construction height (living room) = 262.5 cm
- ceiling = 24.5 + 16.0 cm
- floor = 11.0 + 6.0 cm
= clear room height = 205.0 cm


I am not sure if this is correct …

2. Where do I have a thinking error or is this even correct in the end?
(If it would be correct I would have to increase the raw construction height to 302.5 cm to achieve a clear room height of approx. 250 cm)


Thanks and regards

I think your mistake lies with the ceiling: when you write: The ceiling = raw ceiling + ceiling plaster + ceiling paneling (e.g. wooden ceiling) you mean the total ceiling "thickness".

But you cannot subtract this amount from the ceiling height, only the plaster and the paneling at most. Because otherwise, that would mean you are building your ceiling "downwards" from the top edge of the stone. That is not correct. The precast (concrete) ceilings rest on the row of stones. From then on, your zero dimension applies, and you would then have to subtract a) the floor construction and b) the ceiling plaster and the paneling from the raw building height to get the correct dimension.

Your calculations are individual. For example, we have a floor structure totaling 20cm! The ventilation pipes installed in the ceiling are not 16cm but only 7.5cm (with us). On the ground floor, the raw construction dimension is 2.80m; after deducting ceiling plaster and floor structure, there remains just under 2.60m of actual, usable room height.