To seal aluminium windows and doors, remove any failed sealant, clean and dry the joint, then apply a neutral-cure silicone sealant around the outside of the frame. Draughts through the opening itself usually mean the rubber gaskets or brush seals need replacing. So, winter’s arrived, and you’re noticing a leak in your aluminium window frame. Now what?
Don’t panic! We have the solution for sealing up your aluminium window frame when you don’t have the time to get a professional in.
Continue reading to find out how to insulate aluminium window frames and seal them so you have no future problems.
When Do Aluminium Windows and Doors Need Sealing?
Reseal when you feel draughts around the frame, see water getting in after rain, or notice the existing sealant has cracked, shrunk or come away from the wall. Condensation on the inside of the glass is usually a ventilation problem rather than a sealing one.
The two most significant ways to know if you need to seal your aluminium window frames are draught and condensation.
A draught is noticeable when you hear the air coming through the frame or if the room is significantly colder than other rooms with aluminium windows.
You can hold a lit incense stick while slowly circling the window frame edges to detect a draught. If there is a draught, the flame will move to signify approaching air.
Water on the inside sill after rain, damp patches on the reveal and cracked or shrinking sealant around the outside of the frame are other clear signs. Condensation on the inside of the glass is usually caused by humidity in the room rather than a failed seal; see our guide to preventing condensation on aluminium window frames.
How Do You Seal Aluminium Windows and Doors?
Rake out the old sealant, clean and dry the joint, mask both edges with tape, then run a continuous bead of low-modulus, neutral-cure silicone between the frame and the wall. Tool it smooth, remove the tape before it skins and leave it to cure for 24 hours.
Here is a step by step to sealing your windows:
What you’ll need:
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Silicone sealant
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Sealant gun
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Masking tape
- Sealant remover or a plastic scraper
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Cleaning supplies
What to do:
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Clean the entire window and frame of any dirt or dust. Remove soap residues with a damp cloth before you start sealing.
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Look for gaps where the draught or condensation is coming in.
- Rake out any old, cracked sealant with a plastic scraper or sealant remover, taking care not to scratch the powder coating.
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Stick tape around the sealant edges of where you want the sealant to go to prevent any wonky lines.
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Apply sufficient sealant around the window and smooth carefully to get it as even as possible. Using a sealant gun can help you distribute the right amount of pressure and product.
If you're sealing aluminium doors rather than windows, gaps around the outside of the frame are sealed the same way. Draughts through the door itself usually mean the rubber gaskets or brush seals in the frame are worn and need replacing, as explained below.
Note: you shouldn’t try applying silicone sealants to damp surfaces. If the window or frame is wet to the touch, the silicone will slide off. It needs to be as dry as possible.
If the sealant appears wet, you’ll need to do it again.
For more DIY help, see our guides on insulating aluminium window frames and stopping water leaking from aluminium windows.
What Is the Best Sealant for Aluminium Windows and Doors?
A low-modulus, neutral-cure silicone sealant is best for sealing aluminium frames to brick or render, because it stays flexible as the metal expands and contracts and won't attack the finish. Avoid acetoxy silicones (the type that smells of vinegar) on aluminium, and don't use decorators' caulk on external joints, as it cracks and lets water in.
How Do You Replace the Seals on Aluminium Doors?
Identify the seal profile, pull out the old gasket, clean the channel, then press the new gasket in, starting at a corner and working round without stretching it. Brush seals on sliding doors slide out of their channel and are replaced the same way.
- Take a short sample of the old seal, or measure the groove width and seal shape, so you can match the profile.
- Pull the old gasket out of its groove by hand. If it has perished, use a plastic scraper to remove the pieces.
- Clean the channel with warm soapy water and let it dry.
- Press the new gasket into the groove with your thumb or a seal roller, easing it round corners rather than stretching it, which causes gaps as it relaxes.
- Close the door and check for an even, light compression all the way round. If it still won't seal, the door may need adjusting; see our bifold door hinge adjustment guide.
How do you draught-proof aluminium doors without replacing the seals?
Adjust the keeps or hinges so the door closes more tightly against the existing gaskets, add self-adhesive draught strip to gaps around the frame, and fit a brush or rubber seal along the bottom of the door. Our guide on draught-proofing aluminium windows covers more options.
Which Windows and Doors Are More Likely to Need Sealant or a Door Seal?
Older windows and doors, frames with perished rubber gaskets and those on exposed, weather-facing elevations are the most likely to need resealing. Frames without a thermal break also tend to suffer more from draughts and cold spots.
Draughts are more common in older windows or windows that don’t have specific glazing. Thank goodness for triple and double glazing.
Selecting triple and double glazing can make a massive difference for sealant issues.
If your frames are old or the gaskets have perished all the way round, upgrading may be better value than repeated repairs. Modern aluminium doors come with new weather seals, thermally broken frames and double or triple glazing.
Browse our aluminium bifold doors, aluminium French doors and aluminium sliding patio doors.
Sealing Aluminium Windows and Doors FAQs
How do I know if my aluminium window needs sealing?
There are two ways to tell: draughts and leaking. If you notice any air passing through or water getting in around the frame after rain, a seal is needed.
What do I use to seal my aluminium windows?
There are multiple products on the market, but a silicone sealant is best for a window with a leak. Also, using a sealant gun helps keep things even.
Can I seal a leak in my aluminium window myself?
Yes, you can. However, this is only if the leak or area that needs sealing is relatively small. Extensive open spaces around your aluminium window won’t close with at-home silicone sealant. It’s always best to call your aluminium window installer to find the best way forward.
How long does silicone sealant last around windows and doors?
A good-quality external silicone typically lasts many years, but sun, frost and movement eventually make it shrink or crack. Check the joints every year or two and reseal any sections that have split or come away from the wall.
Can you seal aluminium windows in winter?
Yes, but only on a dry day when the frame and wall are completely dry. Most silicone sealants need temperatures of at least around 5°C to cure properly, so check the cartridge and avoid frosty or wet conditions.
Why is water still getting in after resealing?
The leak may be coming through blocked drainage slots, failed glazing seals or worn gaskets rather than the joint around the frame. Our guide on stopping water leaking from aluminium windows explains how to trace the source.
