Knee Wall – Attic Arrangement with a Knee Window
The knee wall is an integral element of houses with usable attics. It is where the increasingly popular knee windows are installed, which perfectly illuminate the interiors, increase their arrangement possibilities, and improve the aesthetics of the building. How to adjust the height of the knee wall? What to remember when raising it? How to install knee windows in it? More in the article below!
What is a knee wall?
A knee wall is a type of load-bearing wall located above the highest ceiling of the building. Its task is to transfer loads from the roof to the structural element located beneath it. This element is usually a ring beam – a type of reinforcing ring for the ceiling, located at its level along all structural walls and the perimeter of the building. A knee wall is used when the roof structure has its support.
What is the optimal height of a knee wall?
The height of the knee wall depends on the purpose of the attic. In a non-usable attic, intended for utility purposes, the height of the wall usually does not exceed 70 cm. The situation is different with a usable attic. In this case, due to the comfort of using the space, the height of the wall should be appropriately greater. Most often, the wall has a height of 80-110 cm. The higher the wall, the less free access to the window, but also greater functionality of the interior, allowing for the placement of a desk, bed, or even a bathtub directly under the wall. This is also an opportunity to install the so-called knee window, combining the advantages of roof windows and traditional vertical joinery.
Raising the wall for a knee window – what to remember?
Many investors, wanting to gain additional space in the attic, decide to raise the knee wall. However, it is important to check in advance whether such a change is in accordance with the building conditions. This will help us avoid potential consequences of unauthorized construction. Therefore, it is best to consult any changes with an architect.
We should also keep in mind that raising the knee wall changes the proportions of the building. A wall that is too high may break under the weight of the roof. It is therefore necessary to maintain the proper proportions of the building, which will affect the safety of the entire project and the harmonious appearance of the house's structure.
Raising the wall, in which knee windows will be placed, is recommended in the case of low and sprawling buildings. This applies wherever the roof pitch is quite steep. In narrow and tall buildings with a gentle slope roof, raising the wall is not recommended.
Roof windows in the knee wall
Knee windows are intended for installation in the knee wall. They serve as an additional element "extending" the roof windows, to which they must be matched. They are tightly joined together using a special collar. A wide selection of sizes and materials from which they are made facilitates the choice of the appropriate product.
In the case of a high knee wall, proper illumination of the interior is particularly important. An improper number of windows or their poor placement will deprive us of the ability to freely look through the windows.
With a high knee wall, it is worth installing two vertical windows. They are then connected by the frames and positioned one above the other. A good idea may also be the so-called twin installation of knee windows. Horizontally connected sets of windows are then installed using auxiliary rafters.
Installation of knee windows in the wall
Knee windows are used with roofs with a pitch angle from 15 to 90 degrees. The minimum height of the wall in their case is 85 cm. Knee windows are installed in conjunction with roof windows and are joined with a special sealing collar. The key principle of installing this type of window states that the opening beneath it should always be 2-3 cm wider on both sides.
The installation of knee windows, just like other types of windows, should be entrusted to specialists.
Remember that only handing over the installation to professionals will allow us to maintain the manufacturer's warranty for the windows. Of course, we will also gain the assurance that knee windows will be properly embedded in the knee wall and roof slope.