Replacing window seals: installation and replacement made easy

Replacing window seals - how does it work?

Before installation: To replace seals on windows and doors, it is necessary to carefully remove the old, porous rubber. Make sure that no residue of the old adhesive and rubber remains. The old sealing material is often brittle and difficult to remove, but the only way to remove it is with a pointed object. It is advisable to cut the sealing tape with a cutter knife and treat it with silicone spray to make it easier to remove. Although this process is tedious and labor-intensive, it makes it easier to install new sealing profiles. Another tool for removing the old rubber seal and rolling in the new one can be found here.

Then cut the new sealing material to size and fit it piece by piece. Regular maintenance of the seals can extend their service life and save heating costs. Further details are explained in the following section.

The explanation for UPVC windows is given first and then below for wooden windows. You can find videos here:

Expert advice: How to replace and seal your UPVC windows yourself

We recommend watching our video on how to install UPVC windows yourself first:

There are various ways to install window seals on UPVC windows. The seal shape or seal size often determines the appropriate installation method. We basically differentiate between four types of gasket:

1. frame (part attached to the building structure)
2. window sash (movable part of the window)
3. center seal (arranged in the middle of the window, in this case the frame seal is omitted)
4. glass (for fixing the glass pane - very difficult to install

Basics: Start at the top center by pressing the sealing foot of the window seal into the groove. Now lay the sealing material all the way around by pressing the sealing foot continuously into the groove. The corners are fitted differently depending on the sealing profile (see below). At the end, leave 1 cm of the sealing strip protruding. The protruding part is also pressed into the groove. If necessary, the sealing joint and corners can be additionally glued to prevent the window seal from moving due to weather influences.

It is important to ensure that the sealing material is not pulled long, as the window seal could otherwise contract again and create a gap. We therefore cut off 1 cm more.

Another tip for insertion is to sprinkle a clean cloth with a drop of washing-up liquid and a little water and pull the gasket base through the cloth. This allows the rubber seal to slide more smoothly into the groove.

Installation in the corner area

Corner variant 1 - Fold over and cut out the sealing foot

The process consists of four steps: Starting at the top center, the sealing foot of the window seal is pressed into the groove. At the corners, the gasket base is removed to place the gasket around the corner.

This is how it works: In the corner area, only remove the gasket foot over a width of 1.5 to 2 cm - the gasket body remains in place. We remove the gasket base because the gasket material adapts to the window and is not excessively bulky. Repeat this step at all four corners.

Back at the starting point - at the top center - leave 1 cm of the window seal protruding and fix it in the groove (see basic principles).

Please note: The newly installed seal may become wavy because there is too much material in the sealing groove and the material is flexible. Wait one or two days and check the rubber seal. If the material is still wavy, shorten the 1 cm (0.5 cm) protruding from the top center to 0.5 cm (5mm). Then press the seal back into the groove and glue it in place. The window can be closed as usual while waiting 1-2 days until it is perfectly fitted.

Corner variant 2 - 45 degree angle

With large gaskets, e.g. center gaskets, it is not possible to fold them over in the corner area. In this case, we recommend cutting the window gaskets to 45 degrees in all four corner areas and gluing the gasket joint.

How can I cut my window seals to 45 degrees?

You can use our mitre template to cut the window seals to 45 degrees. This allows you to cut the seal precisely so that the corners fit together perfectly and ensure a tight connection.

The following tools are required for installation:

1. tape measure or folding rule to measure the seal
2. household scissors to cut the seal to size
3. optionally, some washing-up liquid or silicone spray to rub into the gasket groove (if the new gasket is difficult to press into the gasket groove)
4. optional: seam roller (also used for wallpapering): this can be used to press the window seal evenly into the groove.
5. optional: templates for the miter cut

After installation, please check the tight fit of the seal. The final gluing of the seal should only be carried out after the entire window seal installation has been completed.

The installation of glass window seals

It is not advisable to replace the window seals for the glass pane without prior experience of replacing seals. Removing the glass pane is more difficult and requires experience. Consultation with specialist personnel is advisable.

Professional tips for replacing window seals on wooden windows

Here you will find videos on how to correctly determine your seal with explanations on the groove and rebate height and how to install wooden window seals yourself.

Simple corner variant - 45 degree angle with template

Here you have the option of installing the seal individually. Four sealing parts are required, consisting of two horizontal and two vertical parts.

It is advisable to glue the seals together only after all the windows have been installed, as the adhesive dries very quickly. Spot gluing means 1 drop of adhesive in each corner area between the back of the seal and the window frame. In addition, one drop in the middle between each of the four corner areas to sufficiently fix the seal. It is not necessary to glue the miter cut.

Information on the template: We have developed a template for the installation of new window seals, which is a cost-effective and practical solution for everyone. This template makes replacement easier and ensures tidy and efficient work. This means that even non-professionals can replace the seals easily and professionally without having to buy expensive tools.

The background to this is that gasket replacement on wooden windows is usually carried out by carpenters or joiners who have experience and the necessary tools. An expensive mitre cutter is required for the cut in the corner area, which makes the purchase uneconomical for the individual.

Corner variant - V - cut

During installation, it is important to ensure that the wooden window seal is installed without a gap in the corners and at the joint edges. The gasket joint should be at the top and the window gasket should not be compressed or overstretched during installation. The gaskets can be easily replaced in the straight area, which is why we will only focus on the different variants in the corner area in our examples.

To install the window gasket in the corner area, a V-cut is made and the gasket is then folded over. To do this, about 2/3 of the seal is cut out with the V-cut to fit the corner. The upper part of the seal (approx. 1/3) is left in place so that the window seal remains as a whole.

The process is carried out in four steps: Starting at the top center, the sealing foot of the window seal is pressed into the groove. The V-cut is made at the first corner. The V-cut is made by hand (a triangle may help here for the 45° cut). After joining, the joint edges can be glued.
You can find installation instructions here:

Why is it important to check and replace window seals regularly?

It is essential to regularly check and replace the seals on windows and doors. They contribute to good insulation, fewer draughts, energy efficiency and a pleasant indoor climate. They also prevent mold growth and damage caused by moisture ingress.

When should window seals be replaced?

Window seals should be replaced if they have become hard or severely deformed, if gaps are visible between the frame and seal or if the paper test shows an inadequate seal. This way you can save energy and avoid draughts.

How can I save energy costs by replacing the window seal?

By replacing leaky windows, you can save energy costs by preventing heat loss, cold and damp and reducing the need for heating or air conditioning. Choose a high-quality rubber seal or a seal made of silicone and make sure it is fitted correctly (see above) for optimum insulation.