How to Install uPVC Windows [2023]

Installing uPVC windows can be a rewarding and cost-effective home improvement project. uPVC windows offer energy efficiency, durability, and low maintenance, making them a popular choice for homeowners. In this step-by-step guide, we will walk you through the process of installing uPVC windows, ensuring a successful installation that enhances the aesthetics and functionality of your home.

Steps to Install uPVC Windows

1. Preparation and Measurement

Before starting the installation, it is crucial to carefully check the new frame measurements against the survey size and the actual aperture sizes. The new frame should be approximately 10mm smaller than the opening to allow for expansion. Additionally, ensure that the new frame and glass are free from any obvious quality issues.

2. Removing the Old Frame

Using a sharp blade, break both the internal and external seals between the old frame and the building. If possible, remove any visible fixings without damaging the surrounding area. Once the frame is removed, clear away debris and old sealant from the opening.

3. Silicone Application

To prevent water and air leaks, carefully apply silicone along the cill up-stand and at both ends. This helps create a seal between the cill, frame, and surroundings.

4. Prepare the External Cill

Cut the external cill to size, ensuring it fits perfectly. It can be a straight cut or rebated if being fitted with projecting horns. Secure the cill end caps in place using a strong adhesive, such as super glue.

5. Placing the New Frame

Offer up the new frame and cill into the opening, using plastic packers to ensure the frame is level and plumb. Maintain an equal expansion gap around the frame to accommodate any movement.

6. Securing the Frame

Turn the frame over and secure the cill to the frame using appropriate uPVC screws. Use plastic packers between the frame and the building at all fixing points to prevent distortion when tightening the screws. Fix the frame in place, with fixings located approximately 150mm in from each corner and spaced at 600mm intervals. Avoid fixing within 150mm of any mullions or transoms. Ideally, use at least 2 fixings per side.

7. Installing the Glass

Offer up the glass and rest it on bridging packers, ensuring it is raised above the internal drainage channels. Insert plastic glass packers between the edge of the glass and the bridging packers to secure the glass in position and square it up in the frame.

8. Testing and Adjusting the Glass

Ensure the glass sits square in the frame and test the sashes to ensure they open and close correctly. Follow guidelines for “toe and heeling” the glass to avoid operational issues. If needed, insert additional glass packers in the top corner of the handle side to adjust the sash’s position.

9. Finishing Touches

Break off any excess packers, clean the frame and glass, and seal both inside and out with a silicone sealant. Apply masking tape to the frame for a neat finish and seal along the underside of the external cill. Finally, fit any trickle vents and refit the internal glazing beads in their original positions using a rubber mallet/hammer to tap them into place.

Hire A Professional Window Fitter

While the prospect of installing uPVC windows yourself can be appealing, especially if you have a knack for DIY projects, the task can indeed be quite daunting for some people. If you are unsure of your ability to handle the installation, or if you simply do not have the time or inclination, hiring a professional window fitter is an excellent option.

A professional window fitter will not only ensure that your windows are installed correctly, but they also usually include additional services within their fee. This typically costs approximately £100 per window, which can be a worthwhile investment considering the services you receive.

Firstly, the window fitter will conduct a survey of your existing window setup. This process involves careful measurements to ensure that the new uPVC windows fit perfectly into the space. They will consider any potential issues such as uneven sills or warped frames, which could impact the final result.

Once the survey is completed, the specifications are sent to the manufacturer to custom build your uPVC window. The window fitter usually manages this process, working closely with the manufacturer to ensure the window is made to the precise measurements and specifications.

Finally, once the window is ready, the window fitter takes care of the delivery process. The transportation of windows can be tricky due to their size and fragility. However, a professional window fitter has the necessary equipment and experience to handle the windows safely, ensuring they arrive at your property in perfect condition, ready for installation.

Additionally, hiring a professional window fitter often comes with a guarantee on the window installation itself. This typically lasts for three months and provides you with extra assurance on the quality and durability of the installation. Should any issues arise with the installation during this guarantee period, the window fitter is obligated to address and resolve them, usually at no extra cost.

In conclusion, hiring a professional window fitter can ultimately save you time, effort, and potential mishaps. It provides peace of mind knowing that your new uPVC windows will be installed correctly, efficiently, and with a backed guarantee, maximising their lifespan and performance.


Installing uPVC windows can be a manageable DIY project with the right tools and guidance. By following the step-by-step instructions provided in this guide, you can confidently install uPVC windows, enhancing the appearance, energy efficiency, and overall value of your home. Remember, if you encounter any challenges during the process, it’s always advisable to seek professional assistance to ensure a successful installation.


What is a uPVC window?

uPVC, or unplasticized polyvinyl chloride, is a type of plastic that is especially known for its durability, energy efficiency, and cost-effectiveness. A uPVC window is a window made from this material.

Why should I consider installing uPVC windows?

There are several reasons why uPVC windows are a good choice. They’re known for their excellent insulation properties, which can help reduce your heating and cooling costs. They’re also resistant to weather, don’t fade under sunlight, and require very little maintenance compared to traditional wooden windows.

Do I need special tools to install uPVC windows?

For installing uPVC windows, basic DIY tools are often enough. These include a measuring tape, a level, a drill, a hammer, and a screwdriver. However, it is important to note that correct installation is key to the windows’ performance and longevity. If you’re not confident in your abilities, it may be better to hire a professional.

How do I correctly measure my window space for uPVC window installation?

To get an accurate measurement, you should measure the width and height of the window space from brick to brick in at least three different places (top, middle, and bottom for width; left, right, and centre for height). Use the smallest of these measurements when ordering your window to ensure a proper fit.

Can uPVC windows be installed in any type of building?

Yes, uPVC windows are versatile and can be installed in almost any type of building, including residential homes, commercial buildings, and industrial structures. They come in various styles and sizes to accommodate different architectural requirements.

How long does it take to install a uPVC window?

The time it takes to install a uPVC window can vary depending on the size of the window, the condition of the existing window frame, and the installer’s skill level. However, on average, it can take between 1-2 hours per window for a professional to complete the installation.

Can I replace my existing windows with uPVC windows?

Absolutely. uPVC windows can replace almost all types of existing windows. However, the existing frames and window openings may need to be modified to fit the new windows. If you’re replacing old wooden windows, you may also need to consider additional insulation or sealing.

How do I maintain my uPVC windows after installation?

One of the advantages of uPVC windows is that they require little maintenance. Regular cleaning with a mild detergent and warm water is usually sufficient. For moving parts like hinges and handles, occasional lubrication with a suitable product can keep them functioning smoothly.

Are uPVC windows environmentally friendly?

A9: Yes, uPVC windows are considered environmentally friendly because they’re recyclable. Furthermore, their excellent insulation properties contribute to energy efficiency by reducing the need for heating and air conditioning, which in turn lowers carbon emissions.

What if my uPVC window gets damaged? Can it be repaired?

Depending on the nature and extent of the damage, some repairs might be possible. For example, minor scratches can often be polished out, and faulty seals can usually be replaced. However, if the window frame or glazing is seriously damaged, replacement might be the only option.



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Astframe is a uPVC Windows & Doors manufactured based in Norwich.

We supply a range of premium quality products including uPVC Windows, Doors, and Conservatories. Aluminium Bi-Folding Doors, Patio Doors.

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