Fitting Double-Glazed Windows – What You Need to Know

If you buy double glazing and you are a competent DIYer then it is possible to install replacement windows yourself – providing you have the right experience and window supplies. Fitting a window can be difficult to get right, but with the best tools and proper technique removing and replacing existing windows is relatively straightforward. 

There are a few important things to remember before you consider attempting to install a double-glazed window unit. Key considerations before you fit a window include the following:

• Fenestration Self Assessment Scheme (FENSA) registration is necessary: FENSA ensures that all installers meet the minimum standards for quality and comply with the current standards. This is non-negotiable and very important to ensure that your installation legally complies with building regulations.
• Proper supply and storage of double-glazed window frames are essential: As sealed units, double-glazing is sensitive to damage. Ensure your supplier is fully qualified and FENSA registered themselves, look for companies that offer a specific trade windows service – as this indicates quality and reliability. 

As leading providers of UPVC window installations, we are a good source of information on fitting a window properly and can explain the process. For a professional solution to fitting a window in the southeast of the UK, please feel free to get in touch for a fast, free and precise online quote today.

How Fitting Double-glazed Windows Works

Now that you have confirmed that you are FENSA registered and have a qualified double glazing supplier, we can explain the process of installing the windows in a bit more detail. If you do not meet these criteria, you will be unable to fit double glazing yourself and will require a professional solution.

When fitting double-glazed windows the process works as follows:

1. Removing the old windows: A critical part of the installation process is to remove the existing windows carefully. Rushed or poor quality removal will damage the walls, which creates a mess and makes it harder for the windows to fit properly – it may also impact the installation’s energy efficiency.
2. Prepare the frame space: You need accurate measurements of the space where the window will go, which you can then check against the frame. Remove any leftover sealant, debris or expanding foam from the walls and check the measurements once again to make sure the new frame will fit.
3. Prepare the sill: To prepare the sill, glue on the sill end caps and cut the sill to fit the length of the frame space. The sill can either be placed straight onto the wall or rebated, so it overlaps around the edges of the frame space. Seal the edges and length to prevent any moisture from seeping into the room.
4. Fitting the frame to the opening: After securing the window sill and adding any extenders to the frame you can set it in the opening, making sure it’s level. You may need packers if there are any gaps. After this tightening the frame and sealing it at the top, bottom and sides will make sure it is fully watertight. 
5. Install the glass: Remove the beading, these will go back later in the same place. Clean the frame of any bits of dirt, debris dust or other small particles. Put bridging packers in the opening and install the glass against them, use glazing packers if there is a gap, secure the packers and put the beads back
6. Seal the frame: Once the beading is back on you can clean the glass again and seal the frame into the internal wall. If you are using any internal trimming you can cut and fit them at this stage. Finish by installing and testing any trickle vents.
7. Finish the installation: You can remove any remaining protective plastic and break off protruding packers both inside and outside to finish fitting your double glazed window unit. Clean the glass and frame on the exterior and seal between and the exterior walls, as well as below the window sill.

At all stages checking the condition of each part of the unit will make sure that every aspect of it functions correctly – this includes the frame, sill, glass and screws. You should check that the window opens and closes properly, make any adjustments and finish. 

The process of fitting double-glazed windows is a straightforward one with the right approach. Wooden windows can be simple to fit, thanks to their lightweight, but they are easier to damage – so be extra careful with wooden frames if you normally install UPVC designs,  as UPVC is much more sturdy and almost impossible to break.