External doors and windows are typically installed before façade insulation. At the very least, this is done before exterior plastering and painting. Internal doors and windows are normally installed after the cladding, plastering, and painting work are completed. Door or window dimensions must be 1-2 centimetres smaller than the available opening size. Therefore, openings should be carefully measured before doors or windows are purchased. The unplastered state of external openings is typically used as a basis for measurement, while plastered internal wall openings provide the required dimensions.
It is crucial to correlate the external wall insulation with external door and window installation to eliminate thermal bridges. Ideally, frame structures should be positioned in line with the external thermal insulation using brackets, or installed directly behind it so that the insulation can cover at least 7-8 centimeters of the frame. In the latter case, a frame extension may be necessary. The frame can also be placed further inside the wall opening. In this case, it is recommended to turn in a minimum of 5 centimeters of thermal insulation and butt it against the frame, again using a frame extension. If it is not possible to achieve the required overlap or thickness, or if there is no external insulation, it is advisable to use insulation under the jambs. This is typically 5 cm thick and is usually made of plasterable extruded polystyrene.
I. Installation of external windows
- Size check: check that the manufactured or purchased window frame fits the dimensions of the opening. The frame size must be 1-2 centimetres smaller on each side than the size of the opening (nominal size).
- Self-adhesive vapour controller tapes are affixed around the outer perimeter of the frame: this comprises a vapour barrier on the interior side, and a water barrier with vapour-permeability on the exterior.
- Drill at least two holes on each side jamb without sashes to fasten with screws. If fastening tabs are used instead, attach these to the casing.
- Place the frame in the opening at the desired location. Check the symmetry and verticality before wedging the frame in two places on each side. Next, adjust finely: use a spirit level and tap each wedge with a hammer until the position and angles are perfect from all directions and correspond to the planned dimensions.
- Secure the casing using a prepared solution: either driving in the fastening screws, or folding the fastening tabs onto the wall and screwing them in place.
- Fill the gap around the frame with thermal insulation material (blown polyurethane foam is ideal). Once the foam has hardened, remove the wedges and fill their places with foam as well. Finally, cut off any excess polyurethane foam.
- Press the self-adhesive vapour barrier tape onto the wall surfaces and seal connections.
- Install the sash or sashes and adjust them so they open and close properly.
Exterior doors are generally installed in the same way as windows. The main differences are in the threshold, the connecting frame piece, and the special fittings. Once the windows have been installed, the window ledges can be installed on the inside and the window sills on the outside. After this, exterior insulation, plastering, and painting work can begin.
II. Installation of interior doors
Modern rabbeted jamb interior doors are installed in the same way as exterior doors, i.e. they are positioned using wedges, precisely adjusted, fastened and filling the gaps around the frame with thermal insulation material (polyurethane foam). Once installation is complete, the thermal insulation strip is covered with casings which are secured with nails. Modern flat jambs and adjustable frames use polyurethane foam for tightening.
The process is shown for adjustable frames:
- Position the frame structure without casing in the wall opening. Place spacers under the jambs to raise them 2-3 millimeters off the floor.
- Temporarily secure the frame with 2 wedges on each side and adjust precisely. Consider size and symmetry to ensure the jambs are vertical and the frame connector is level.
- Place at least 3 crossbars between the jambs.
- Inject polyurethane foam into the gap between the jamb and the wall at each point. If greater sound insulation is required, fill the gap completely.
- Secure the frame to the wall structure using screws.
- After the polyurethane foam has dried (30-40 minutes), remove the wedges. If necessary, fill the gaps left by the wedges, then cut off any excess polyurethane foam.
- After installing the door leaf, check that it opens and closes properly. Adjust the hinges if necessary.
- Install the casings, adjusting their position to the thickness of the wall.
- It is advisable to fill the area under the frame legs with silicone.
