How do you measure window openings in the building accurately?

One of the key stages of building or comprehensively renovating a building, e.g. with a view to thermal modernisation, is installing the window joinery. Doing this in line with the required standards has a direct impact on both limiting the energy demand of the building and the comfort of its occupants. To avoid problems in the implementation of this process, which may generate high costs, it is useful to know how to measure the window openings accurately. In the article, we explain why it is significant and present practical tips connected with the implementation – enjoy reading!

Why does a window need to be properly fitted to the size of the opening it will be installed in?

Installing window joinery in an opening that is too small will obviously be impossible without first enlarging it. However, with the reverse situation, many people think that filling the cavities with mounting foam is good enough. This is what is usually done, as, for certain reasons, a minimum distance has to be maintained, but if it is too large, it may generate numerous problems. This is why an accurate window measurement is so important.

What may be the consequences of an inaccurate measurement of window openings?

In such cases, window joinery installation is severely hampered, which promotes making mistakes. It is worth taking the time to accurately measure window openings, as inaccuracies in this respect may result in:

  • a necessity to perform unplanned masonry works, which entails considerable additional costs,
  • a disruption of the continuity of the acoustic and thermal insulation – this risks increasing the noise level in the premises and generates the risk of forming so-called thermal bridges, which make it difficult to maintain an optimum indoor temperature (the building consumes more energy),
  • aesthetic deterioration of the windows due to their poor fitting and reduced comfort of using them (e.g. poorly levelled windows will self-close when opened).

Window opening measurement – how do you do this accurately?

In the vast majority of cases, window joinery is square or rectangular. If this is what you want to install, get yourself an angle bracket ready before you reach for the tape measure. Use it to check if every corner of the opening has a right angle. If necessary, you can also check if both diagonals are of identical length. If major deviations in this area are found, it is essential to schedule masonry work to correct them. Only then can you proceed to measure the space for window installation. How do you do it accurately?

Using the measuring tape, measure the width, height and depth of the window opening. Do it in three different points (preferably at the edges and in the middle) – if you notice differences, write down the smallest obtained value. After this process has been completed, it is essential to repeat the window space measurement – this will give you greater confidence that it has been done correctly.

What are the most frequent reasons for an incorrect window opening measurement?

It is usually a result of human error. In order for the window opening measurement to be correct, it should be performed in a focused manner and without time pressure. Excessive haste, distraction or simple inattention are the main reasons for the inaccuracy of this process.

The second most frequent reason is questionable accuracy of the measuring tools used. Thus, try to steer clear of using low-quality brands.

Measuring a window opening, where there used to be an older type of window, can also be a problem. For the measurement to be correct, the space for the frame installation should first be cleaned very carefully of all residues of various building materials and only then should its dimensions be determined.

It is essential that the window be slightly smaller than the opening where it is to be installed

When addressing this topic, it is worth highlighting the fact that it is a mistake to install a window frame that is perfectly sized to fit the opening in the wall. There has to be a minimum gap, referred to as an expansion joint, between these pieces. After performing a correct measurement, you have to take this into account – normally it is from 10 to 20 mm and depends mainly on the window type. What is the purpose of keeping such a gap?

If the expansion joint is too small, properly sealing the window frame will be impossible. If it is too large, in turn, fitting the frame, and more specifically its solid anchoring, will become a problem.

Go for high-quality Aluprof joinery!

Sticking to the above tips will surely make performing a correct measurement of window openings easier for you. However, keep in mind that properly fitting windows and getting them professionally installed is not enough to be sure they are perfectly sealed and functional. What is also crucial is their quality, so you should always choose products from valued manufacturers. You can find them in our Aluprof offer – we are the industry leader, offering the highest quality aluminium systems for windows! Contact our representatives, who will provide you with professional support.

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