From which parapet height is considered a full floor?

Hello everyone,

I have gone through all the topics I could find here related to full stories / knee wall height / knee wall height and unfortunately did not find an answer to my question. Maybe you can help me with the answer.

How high can the knee wall in the upper floor be without the floor being classified as a full story? (Assuming no dormers)

The building code NW 1962 applies, the land use ordinance 1968, and the development plan only prescribes the following:

- 1 full story
- Roof pitch 30 degrees
- Gable roof

There are no further limitations (such as ridge height, etc.) and the ground floor is 12x12m.

Thank you very much!

The knee wall height is not the determining factor, but rather how many percent of the area, compared to the floor below, has a regular ceiling height. If the area is more than 2/3, it is generally considered a full storey.
Simply calculated, your ground floor has 144 sqm of area, so from 96 sqm with normal wall height of 2.30 or 2.40 m, the attic becomes a full storey. The detailed calculation is of course more complex.

Thank you for the quick response and the valid note on the 2/3 rule.

What is the maximum knee wall height resulting from the situation that only one full floor is allowed?

and unfortunately I have not found an answer to my question.

This may be because it depends on the base area of the new building and cannot be answered in general terms.
For you, it is not 2/3 (as in other states), but 3/4…
You can roughly determine this yourself with graph paper and a set square. The architect you trust will give you a binding answer…. Impossible for a forum.

North Rhine-Westphalia
Building Code NRW, § 2 Terms, paragraphs 5, 6

(5) Full storeys are storeys whose ceiling upper edge projects on average more than 1.60 m above the ground surface and which have a height of at least 2.30 m. A top storey (setback storey) recessed compared to the outer walls of the building is only a full storey if it has this height over more than two thirds of the base area of the storey below. A storey with sloping roof surfaces is a full storey if it has this height over more than three quarters of its base area. The height of the storeys is measured from the upper edge of the floor to the upper edge of the floor of the storey above, in storeys with roof surfaces up to the upper edge of the roof covering.

The building code NW 1962, the land use ordinance 1968 apply and the development plan only stipulates the following: - 1 full storey - Roof pitch 30 degrees - Gable roof

Your development plan is therefore about half a century old - in that case I would see good chances for exemptions, especially if more generous conditions have already been created in the surrounding area. But it is already not restrictive:

How high may the knee wall / dwarf wall on the upper floor be without the floor being counted as a full storey? (Assuming no dormers) [...] There are no further limitations (such as ridge height, etc.) and the ground floor measures 12x12m.

Then let's calculate backwards: 12 m building depth, 3/4 may have 2.30 m height, floor area identical to the ground floor, so 9 m depth of the relevant area. A 30° roof pitch comes to 1.5 m about 87 cm lower, that would be roughly 1.43 m knee wall according to Eva Zwerg or however that milkmaid thing was called. Knee wall heights in the range of around 1.0 to 1.4 m are very practical. Cross dormers can be kept well under 2.30 m height.

Thank you 11ant, that is super helpful!

Would a balcony on the upper floor create room to raise the knee wall further? Or are there other tricks that allow one to increase the knee wall?