how to install wood windows

How to install wood windows?

blog | 21.07.2022

Wood windows, just like any other windows, need to be well installed or they won't fully serve their purpose. Incorrectly installed wood windows can make them leak and be damaged. How to install wood windows to make them last for years? Let's find out!

IMPORTANT: It is best to have timber windows installed by a fitting company whose employees have the required qualifications. The following article is not a manual for the installation of wood windows, but a collection of hints for the installation of windows. It is worth knowing how the installation work should look like.

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How to install wood windows?

As we mentioned before, the correct installation of a wood window is a condition of its proper functioning. Incorrect installation may cause problems with opening and closing the window, condensation on the pane or even rotting of the wood frames. Although installation work should be carried out by professionals, it is worth knowing how it should be done.

ATTENTION: The installation of wood windows should be carried out after the plastering and flooring is completed. Excessive moisture adversely affects the wood.

Ways of installing wood windows

The way in which you install a window depends on where it is set, the type of wall material and the method of finishing the reveal. The installation of a wood window must ensure its stability under the load resulting from its own weight and dynamic forces caused by wind pressure, opening and closing.

This requires stable support in the window opening and horizontal stability through installation with anchors or dowels.

Anchor fixing, i.e. steel flat bars embedded in the frame and screwed to the side of the reveal, is the most common method of window installation. This makes it possible to move the mounting points in the wall away from its edge, which is important when you want to install the window close to the external surface of the bearing layer.

The second method is installation using dowels - steel pins passing through the window frame. In this way, windows are fixed in place of the old ones, which reduces the finishing work later - the treatment around the frame.

How to install wood windows step by step

Before inserting the window, it is important to check that the opening of the reveal has the correct size. Its width should be 2 to 3 cm greater than the width of the frame, its height 3.5 to 5 cm greater than the height of the frame. Then, the position of the frame in the wall has to be cleaned, the window sashes have to be removed from the frame and the frame has to be inserted into the opening, resting on timber support blocks in such a way that each block is placed under each vertical profile.

The frame is pre-fixed in the masonry using wedges that are placed close to its corners and using a spirit level to set its plumb and level. Then, using a tape measure, the diagonals and the so-called reveal of the frame are set. Once the frame has been measured and adjusted, it is fixed permanently in the masonry:

  1. with dowels - after inserting the frame into the wall, holes are drilled in its sides and dowels are screwed into it. This method can be used when the wall is homogeneous, e.g. made of cellular concrete;
  2. with anchors - this involves screwing or hooking them to the outer perimeter of the frame before inserting the frame into the opening. Anchors are placed approximately 25 cm from the corners. Note that the distance between anchors should not exceed 70 cm.

After the frame has been installed, the sashes are fitted. The gap between the frame and the wall is then filled with polyurethane mounting foam along the entire perimeter of the gap up to 1/3 of its depth. The gap is sprayed lightly with water to ensure better adhesion of the foam. Excess foam is trimmed with a sharp knife flush with the window. On the inside, the window opening is finished with strips of plasterboard and silicone is used to seal the junctions between the frame and the wall along the entire perimeter of the windows. 

Sealing the window

How to install wood windows - the most common mistakes

Incorrect planning of window installation

Just as important as the window installation process itself is its proper planning. You need to choose the right moment to place the joinery, both windows and doors. Most often, windows are installed at the shell stage, after the walls have been built and the roofing installed, but before the interior and exterior plastering. At the design stage we should also answer the question whether we are interested in installing external blinds. Some types of external roller shutters, such as overhead shutters, require the window opening to be widened by the size of the box.

See also our range of external roller shutters:


Incorrectly prepared window openings

Incorrect preparation of window openings is a mistake which is made relatively often - and which can be easily spotted at an early stage if only you know what to pay attention to. Remember that window openings must be properly prepared not only for the installation of the window in them, but also beforehand - to take appropriate measurements - only then will we be able to properly place the window in the window opening. The processing of the reveals includes first of all levelling their surfaces. These should be flat, without irregularities, gaps and cracks. Any such imperfections may result in difficulties with window tightness during proper window placement. Pay attention to the levelling of the bottom edge - this is where the window rests, so it is important that it is perfectly even.

Incorrectly performed jamb measurements

Another common mistake is installing windows that are too small or too large in relation to the reveals. This is usually the consequence of incorrect measurements. Measurements of the reveals should be taken after the edges and substrate have been levelled. If you measure the reveal before levelling, it may turn out that there are some changes to the dimensions when levelling the walls - and in this case, even a millimetre can make a difference. Measurements need to be taken very carefully, on both sides of the reveal (external and internal), plus you also need to make sure that the angles of the window opening are actually straight.

Read also:

Jambs measurement, i. e. how to measure a window recess


When installing wood windows in a window recess, there are two main things to bear in mind. Firstly, care is more important than carrying out the work quickly. Secondly, the way in which the window installation will be carried out varies depending on a number of factors. For example, the type of wall (the material it is made of) and where the window is installed (in the roof or in the wall) are important. If you notice any mistakes when installing the windows, don't be afraid to draw attention to them. Some mistakes can be corrected if noted early enough. On the other hand, if you do not react - you run the risk of later problems or even having to replace your newly installed windows.

Read also:

Wood replacement windows

Wood window repair

Are you dreaming of wood windows for your home, but don't know which ones to choose? Get in touch with our salesman.


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