ᐅ Calculation Example: Knee Wall / Short Wall

Hello everyone,

Is it possible to roughly estimate the additional costs involved in planning a knee wall instead of a dormer wall?

Could you provide approximate cost differences for the following examples:

Single-family house
Gable roof
Dormer wall
45-degree roof pitch

Vs

Single-family house
Gable roof
Knee wall 80cm (31 inches)
45-degree roof pitch
For example, +5000€ more?

Vs

Single-family house
Gable roof
Knee wall 1.60m (5 feet 3 inches)
35-degree roof pitch
For example, +10000€ more?

The other key data, such as the exterior dimensions of the house, should remain the same in all three examples (except for the living space, which would naturally increase with a higher knee wall).

It depends entirely on your builder and their surcharge policy. Laying and plastering an additional row of bricks is not a big deal, but on the other hand, knee wall height increases can be a significant source of profit.

Or basically the type of knee wall construction. I don’t have anything made of masonry there, but a "wooden frame" on which the roof truss rests. In the shell construction, the knee wall is 1m (3 ft) high.

Bau-beendet schrieb:

Or basically the type of knee wall construction. I don’t have any masonry there, but rather a wooden frame on which the roof truss rests. During the shell construction phase, the knee wall is 1m (3.3 feet) high.

It should be prefabricated construction. So no masonry.

I can only tell you that the Weberhaus seller back in 2020 mentioned a cost of 2500€ per 10cm (5 inches) of knee wall. Any windows in the tall knee wall would, of course, be priced extra. For our general contractor, the difference between a full and half storey was about 14,000€ (exact height would need to be looked up), with windows priced like masonry. Just to give you an idea of the difference.

ypg schrieb:

A knee wall refers to the exterior wall on the eaves side of a house that is built above the rough ceiling of the top floor, supporting the roof structure. It is a typical feature of roofs with purlins. The higher the knee wall, the more usable floor space is available under the sloped roof. Source: (exceptionally by me) Wiki

because trimming the roof slope reduces the floor area in the attic. However, if you need to accommodate a significant number of usable rooms upstairs, the footprint of the ground floor would need to be larger. Nowadays, many plots do not allow this anymore (due to cost, size, availability). This can also lead to an imbalance in the room distribution between the ground floor and attic (too much space downstairs, too little upstairs).

No comment 🙁

KaraiKa schrieb:

The other basic data, such as the exterior dimensions of the house, are meant to remain the same in all three example cases (except naturally for the living area, which would increase with a higher knee wall).

Then you are comparing three different living areas here, which is like comparing apples and oranges.