It is important to plan the connecting joint between the window and the structure thoroughly and in detail to avoid subsequent damage. In particular, any interactions that can occur here — for example, as a result of the different behaviour of components under the influence of temperature — must be taken into account. The connections must be formed such that no condensation can occur, heat losses can be avoided and the window construction can work freely.
Inside, middle, outside
The surface connection between the window frame and the building shell is referred to as a stop. A distinction is made between an internal stop, an external stop and a blunt window reveal. The type of stop can also influence the position of the window in the wall — flush with the inside, in the centre of the reveal, or flush with the outside. A central arrangement with an internal stop is the type most commonly found in residential constructions. Of course, other, often design-driven solutions are also possible, such as the deliberate protrusion of the window beyond the plane of the outside wall.
The lower closure of the window, which is found on the outside, is particularly subject to rain and other weather influences. To prevent damage to the construction, particular attention must be paid to the following:
- The window profile must reach beyond the window ledge
- The window ledge should protrude at least 20 mm beyond the front edge of the outside wall and slant slightly to the outside (5°)
- Both the window ledge and the window profile must have a drainage area or weather groove
- A lateral upturn of the window ledge prevents moisture from penetrating the construction (for more detailed information, see the guidelines for installing window ledges).
The criteria for selecting the means of attachment are dependent on:
• The wall system
• The construction situation (renovation/new build)
• The frame material
• The load (net weight/additional loads)
This is a concealed type of attachment in which the
frame is screwed through.
Executed in the same way as a screw fitting.
Area of application: Brick, concrete
Sheet metal lugs (wall anchors)
Lugs are relatively flexible. This allows the thermal changes in length of the frame materials to be absorbed. Lugs can only take loads perpendicular to the window plane. Suitable means of attachment must be used to attach them to the wall and the window frame.
If, in multi-skinned wall systems, the window is positioned in the insulating zone, supporting constructions such as consoles etc. are required. The size of the attachment itself must be dimensioned such that the wind forces and traffic loads to be expected are absorbed and the
net weight can also be borne with an open sash perpendicular to the window plane.
Frame connectors are auxiliary frames that are set during the construction phase and that subsequently hold the window. The attachment and the load transfer of the frame connector must meet the previously specified requirements for the wall and the window.
Metallic components in the connecting joint are unavoidable thermotechnical weak points. The attachment devices must therefore be arranged in conjunction with insulating materials such that no thermal bridges are created. In thermally separated aluminium profiles the thermal separation must not be bridged.
Extreme window dimensions, such as long banks of windows, require thorough consideration and planning of the connections as the material expansion due to heat impact can be very high in these cases. Expansion joints can be used, for example; in this case, suitable sealing materials must be selected to allow for the deformation. Even when large-scale ceiling cambering is to be expected, connections must be formed accordingly to ensure that the window construction is not damaged.