The most common mistakes in window installation and how to avoid them
Installation of windows is one of the most important stages of any construction or renovation project. Even the best windows - with excellent thermal, acoustic and aesthetically pleasing properties - will not do the job if they are incorrectly installed. Unfortunately, many builders still treat installation as a secondary issue, focusing mainly on the choice of the product itself. Meanwhile, it is quality installation determines whether windows will be airtight, durable and energy-efficient.
Incorrect installation leads to serious problems such as heat loss, blowing out, damp walls, mould or even damage to joinery. As a consequence, this can generate high repair costs, increase heating bills and reduce the living comfort of the occupants. Instead of saving money, the builder exposes himself to additional expenses that could easily be avoided in many cases.
At GM PLAST we have for years paid particular attention not only to the quality of the offered windowsbut also on professional and precise installation. Our fitters are experienced specialists who are well versed in both traditional techniques and modern solutions, such as warm installation with sealing tapes. This ensures that we our realisations meet all standards and customer expectations - both in Poland and abroad.
In the following section, we will outline the most common mistakes made with the window installationThe effects of these and how to avoid them. If you are planning a replacement or installation of new windows, be sure to read this guide to the end - it will not only save you time and nerves, but also money.
Installation of windows is a process that requires precision, experience and knowledge of modern technology. Unfortunately, many teams make mistakes that can lead to problems such as leaks, damp walls or even deformed joinery. Below we present the most common errors in window installation, their effects and how to avoid them.
1. Failure to adequately prepare the window opening
🔴 Error:
It is often the case that windows are installed in inadequately prepared openings, which may be uneven, dirty or damp. Dirt, old mortar or unevenness can hinder the proper seating of the frame and affect airtightness.
⚠ Implications:
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Difficult to level correctly windows
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Poor adhesion of the installation foam
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Possibility of settlement windows after installation
✅ How can this be avoided?
Before installation of The opening should be cleaned and levelled, any loose plaster removed and its moisture content checked. If necessary, it is a good idea to reinforce the edges of the opening with special profiles or levelling mortar.
2. inadequate sizing windows into the hole
🔴 Error:
Too small or too large windows in relation to the opening cause problems with their correct installation. It is often the case that builders order the windows "on contact", which makes it impossible to make expansion joints properly.
⚠ Implications:
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Excessive stresses in the window frame, which can lead to cracks
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Problems with proper sealing
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Possibility of thermal bridges
✅ How can this be avoided?
Window should be 10-20 mm smaller than the mounting hole to ensure that the installation clearancewhich allows for proper sealing and compensation for material expansion.
3. incorrect levelling and alignment windows
🔴 Error:
Window must be perfectly level and at right angles to the wall. A common mistake is to install 'by eye' or to use the wrong spacer wedges.
⚠ Implications:
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Difficulty opening and closing sashes
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Excessive stresses in the hinges leading to faster wear and tear of the hardware
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Sashes falling out of the frame in extreme cases
✅ How can this be avoided?
To set windows a spirit level and installation wedges should be used. After initial seating, it is necessary to check the plumb and level on several planes.
4. improper attachment of window frame
🔴 Error:
Inappropriate placement of anchors or dowels, or too few of them, can weaken the structure windows.
⚠ Implications:
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Window can deform under weight and stress
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Leakage weakening, formation of leaks
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Risk of window damage in high winds or draughts
✅ How can this be avoided?
Fixing should be done according to the guidelines window manufacturer. Recommended anchor arrangement:
5. inadequate sealing with installation foam
🔴 Error:
Too much or too little polyurethane foam can impair airtightness windows. It is often used the foam itselfwithout additional sealing tapes, which is a mistake.
⚠ Implications:
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Poor thermal insulation - heat loss
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Moisture absorption by the foam, which can lead to damp walls
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Possibility of frame deformation
✅ How can this be avoided?
Use polyurethane foam in the correct amount and vapour-proof and vapour-permeable stripswhich protect the insulation from moisture.
6. Lack of vapour-proof and vapour-permeable tapes (with warm installation)
🔴 Error:
Traditional installation on the foam itself does not provide adequate protection against moisture. The lack of taping causes the foam to soak up water, leading to degradation.
⚠ Implications:
✅ How can this be avoided?
It is worth betting on warm installation, which involves the use of:
💡 At GM PLAST we use warm installation as standard, so that our customers can enjoy the highest energy efficiency windows.
7. No expansion joints or space for thermal expansion
🔴 Error:
Building materials, including PVC i aluminiumThey change their dimensions under the influence of temperature. If window is fitted "in compression", deformation may occur.
⚠ Implications:
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Crackling and creaking of the frame
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Problems with opening and closing sashes
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Cracks in glass or profiles in extreme cases
✅ How can this be avoided?
Keep Adequate installation play as mentioned above especially with PVC windows (10-20 mm) and use flexible seals.
Warm installation - a way to avoid mistakes and improve energy efficiency
More and more investors and homeowners are opting for warm installation windowsinstallation method window joinerywhich ensures not only a solid seat, but above all excellent air-tightness and high thermal insulating capacity. In times of rising heating costs, this solution is becoming not only cost-effective, but essential.
What is the difference between warm installation than the traditional one?
🔹 Traditional installation consists mainly of fixing the window mechanically (with anchors or dowels) and sealing the installation space. exclusively with polyurethane foam. Unfortunately, this foam - although it has good insulating properties - is very sensitive to moisture and does not sufficiently protect against moisture penetration.
🔹 Warm installation is a modern technique that involves the execution of a so-called 'fusion'. three-layer sealing:
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inner layer - vapour-proof tapewhich prevents the penetration of water vapour from inside the building into the insulation layer,
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middle layer - installation foam as thermal and acoustic insulation,
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outer layer - vapour-permeable tape, which protects the insulation from precipitation and UV radiation while allowing moisture to evaporate to the outside.
💡 In practice, this means that warm installation protects against wall moisture, heat loss and mould growthwhich is of great importance for the sustainability of windows and the comfort of residents.
Advantages of using tapes - protection against moisture and heat loss
✅ Increased tightness of the window-wall connection - The tapes eliminate the risk of thermal bridges and uncontrolled air flow.
✅ Longevity of the insulation layer - polyurethane foam does not degrade as it is protected from moisture and UV radiation.
✅ Protection of the wall structure - moisture does not penetrate the masonry, reducing the risk of dampness and mould growth.
✅ Improved sound insulation - The three-layer seal increases protection against noise from outside.
✅ Higher energy efficiency of the building - thanks to airtight window installation heating energy requirements can be significantly reduced.
Reducing heating bills through airtightness
High air-tightness achieved through warm installation translates directly into lower heating costs. In winter warm air does not escape through leaks around the windowsand in summer - the coolness from the air conditioning does not escape.
According to the research, properly executed warm installation can reduce heat loss through window joints by up to 70%which may translate into savings of several hundred PLN per year in an average single-family home.
In addition, airtight installation supports meeting the requirements of WT 2021 (technical conditions of buildings), which is important for building approvals and obtaining subsidies, e.g. from programmes "Clean Air".
why choose GM PLAST?
At GM PLAST we offer professional warm installation as standard - tapes, foams, anchors, all in accordance with the latest standards. We do not regard this solution as an "extra option" - for us it is the basis for modern, energy-efficient construction.
Thanks to many years of experience, modern technical facilities and cooperation with renowned manufacturers (Kömmerling, Decco, Aluplast, Salamander, Aluprof, Aliplast, Reynaers), we are able to offer our clients:
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expert technical advice,
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precise and tight assembly in compliance with current regulations,
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comprehensive service - from measurement to service,
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products that meet the highest standards of thermal and acoustic insulation.
👉 Bet on quality that translates into real savings - choose warm installation with GM PLAST.
The importance of the experience of the installation team
Correct window installation It's not just a question of choosing the right materials and technology - the the experience and knowledge of the installation team play a key role here. Even the highest quality windows will not fulfil their function if they are poorly seated, inaccurately sealed or not installed in accordance with the manufacturer's recommendations.
Why rely on certified and experienced professionals?
🔧 Professionals know the current installation standards and building regulationsso they can avoid many of the problems associated with misplaced joinery.
🔧 Experienced fitters can choose the right technique for the type of wall and the specific building - mounted differently windows in a new energy-efficient house, and differently in an old building with thick walls.
🔧 Certified teams work according to the three-layer installation technology, ensuring tightness, durability and aesthetic finish.
🔧 They know how to prepare the reveal properly, how to ensure that the frame is properly levelled, how to use tapes and foams to avoid later problems with leaks, freezing or deformation.
🔧 Professionals can also react quickly to unforeseen situations - such as unevenness in the masonry, missing right angles or other construction defects.
Errors are most often due to saving on the team
One of the most common reasons for errors in window installation is attempt to save on labour. Choosing the cheapest team or installing it yourself without experience can lead to:
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leaks around the window frame,
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the formation of thermal bridges,
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damp masonry and mould growth,
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cracking of the plaster and deformation of the frame,
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or even to complete disassembly and the need for reassemblywhich generates high additional costs.
💸 Paradoxically - saving a few hundred zloty in the beginning often means Several thousand PLN of losses in the long termnot to mention the loss of thermal comfort or interior aesthetics.
GM PLAST are professionals you can trust
Our installation teams undergo regular training and are familiar with the characteristics of both modern and older buildings. This allows us to perfectly match the technique installation to the technical conditions of the facility in question.
By cooperating with GM PLAST, you gain:
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access to a trained assembly team,
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the certainty that installation will be carried out in accordance with standards and manufacturers' recommendations,
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guarantee of durability and tightness of installation,
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as well as professional technical advice at every stage of the investment.
Don't take risks - trust the proven specialists and choose a comprehensive service window installation with GM PLAST.
How to avoid mistakes? A step-by-step guide for the investor
Installation of windows is one of the most important stages during the construction or modernisation of a house. Not only does the durability of the joinery depend on its quality, but also thermal comfort, noise levels inside the building and the amount of heating bills. Here is tipswhich will help you avoid the most common mistakes and ensure the longevity of your investment.
1. Choose a proven company with experience
Bet on a partner who doesn't just sell windowsbut also deals with their professional installation of. At GM PLAST we offer a comprehensive service - from technical advice to professional installation carried out by trained teams.
Don't just go for the price - experience, good reviews and references are just as important as an attractive offer.
2. ask for warm installation and a written guarantee
Warm installation using vapour-proof and vapour-permeable tapes, polyurethane foam and suitable anchors is the standard in modern construction today.
Ask the contractor for details of the technology and ask for a written guarantee on the work carried out - is an additional safeguard for you as an investor.
W GM PLAST all assemblies are carried out in accordance with warm installation, ensuring airtight and energy-efficient construction.
3. Ensure proper preparation of the walls
Many mistakes result from an unprepared reveal - crumbling, damp or with unevenness. Before installation you should:
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Remove loose plaster fragments and level the surface,
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ensure that the substrate is dry and stable,
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use a suitable primer or levelling layer.
Particularly when it comes to the thermal modernisation of buildings, it is worth consulting a professionalto prepare window openings in accordance with current technical requirements.
4. Check technical documentation and ask for acceptance after installation
Don't be afraid to ask for details - any serious company should provide you with an installation project, indicate the materials and technology used.
After completion of the work, be sure to carry out technical acceptance, preferably with a company representative. Check:
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tightness of joints,
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the workmanship of the window sills,
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operation of fittings and handles,
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cleanliness and aesthetics of workmanship.
W GM PLAST we carry out final inspections and discuss all relevant aspects of the installation with the customer.
5. make sure the team uses certified materials
Sealing tapes, mounting foams, anchors and screws - all of these items should have certificates and approvals proving their durability and compliance with the standards.
Our teams use only proven assembly systemsthat achieve the highest levels of airtightness and thermal insulation.
Summary - investment in good windows This is only the beginning. Equally important is their professional installation. If you want to avoid mistakes, rely on experience, modern technology and full documentation.
Why choose windows from GM PLAST?
Choosing windows is a decision that will last for years - so it is worth betting on a proven manufacturer that combines quality, experience and a comprehensive service. GM PLAST is a company that for more than 25 years has not only provided its customers with durable and aesthetically pleasing windowsbut also full support at every stage of the investment. Here's what sets us apart:
✅ Top-quality PVC profile windows Kömmerling
In our offer you will find energy-efficient and durable window systemsbased on renowned German profiles Kömmerling. With these, your windows will last for many years, providing excellent thermal and acoustic insulation.
✅ Professional installation - in Poland and abroad
We are not only active locally - we implement assemblies throughout Poland and also abroad, mainly in Belgium and France. We offer both traditional assemblyas well as warm assembly¿ as standard, using modern tapes, foams and anchors that meet the latest building standards.
✅ Comprehensive customer service
From the first contact to the completion of the installation, we are at your service. We provide:
With us, everything runs smoothly and without stress.
✅ 25+ years of experience and modern machinery
We are one of the largest PVC joinery manufacturers on the profile Kömmerling in the region. Our production line is based on modern technologiesand every stage of implementation is carefully monitored. Hundreds of satisfied customers are our best calling card.
✅ Windows to suit all budgets
We understand the needs of different customers - that is why our offer includes both economic solutions (e.g. on Decco profiles)as well as premium products. We help select the best solutions for each budget and investor's needs.
Don't risk cooperating with accidental teams - bet on quality, which has already been appreciated by many customers in Poland and Europe. Choose GM PLAST - with us you gain peace of mind, safety and the certainty of an excellent result.
Window installation is key stagewhich has a direct impact on the comfort, safety and energy efficiency of your home. Unfortunately, many people make a serious mistake, looking for savings at this very stage. Improperly seated windows can lead to leaks, thermal bridges, damp walls and even the need for costly joinery replacement - often after only a few years.
That is why it is worth betting on a proven partner that knows what it is doing. At GM PLAST, we have been combining for over two decades premium PVC windows z professional, certified installation. Our experience, state-of-the-art technology and individual approach make us the trusted choice for hundreds of customers in Poland, Belgium and France.
🔧 Don't take risks - go for proven quality.
📐 Request a free quote or contact us, and we will advise you on the best solution to suit your budget and expectations.
Your home deserves the best