Windows play a crucial role in maintaining a comfortable and energy-efficient home, but over time, the seals can wear down, leading to issues such as drafts, leaks and reduced insulation.
In this blog post, we will take you through a step-by-step process to effectively reseal your windows from the outside, ensuring a tight and durable seal against the elements.
Whether you're a seasoned DIY enthusiast or a homeowner looking to address potential energy inefficiencies, our guide covers essential techniques, tools, and tips to help you maintain the integrity of your windows.
If you are wondering whether or not your windows need resealing, read "Do My Windows Need Resealing" for information on why silicone seals fail and the tell-tale signs to look out for.
How To Reseal Your Windows Externally
Resealing your windows is a straightforward process that you can do yourself with the right tools and materials.
Here's a step-by-step guide on how to reseal your windows externally.
Tools You'll Need:
Soft brush & cloths
Putty knife/ scraper or hook knife
Silicone Remover
Bottle of Methylated spirit
Masking tape or duct tape
Sealant gun
Appropriate silicone sealant
Sealant smoothing tool
Foam backer rod (Optional for large gaps around windows)
Stanley knife
Spray bottle of soapy water
Step 1) Cut Away Existing Silicone
Using the retractable window scraper or putty knife, simply run the blade up and down the wall into the silicone, moving along the wall with each up and down motion until you get to the end. Repeat the process along the edge of the window frame. This will ensure that each full line of silicone will come off in one long run.
Do not, and i repeat, DO NOT hack at the sealant with a Stanley knife. This will leave unsightly scratch marks on the window frame. Using the thin blade on a retractable scraper eliminates the risk of creating nasty scratches.
When you get to the corners run the blade in as far as you can. You may need to use the Stanley knife to pick out any stubborn bits that may not want to come out, especially in the corners.
Step 2) Apply The Silicone Remover
Although it may seem like all the silicone has gone from step one. It’s important to now remove any skin or existing sealant residue. If this is not done the new sealant will simply not adhere properly.
It’s worth spending another 20 minutes on this and the following steps to ensure the job is done properly.
Apply your sealant remover gel or spray to the areas where you removed the existing sealant.
Be generous when applying the remover. You want to make sure you hit every inch of the old sealant skin.
The gel of choice for us is the No Nonsense sealant remover which is readily available at any Screwfix. Apply this to the area with the brush provided then leave to work roughly 10 minutes.
To save more time though, we recommend using a spray. If you are able to get your hands on a can, i would suggest using a product called CT-1 Multisolve. It works in pretty much the same way as the gel, but it’s a hell of a lot quicker to apply.
Simply spray and leave for approximately 10 minutes to work.
As you will see, the existing sealant residue will start to dissolve and turn to mush.
Step 3) Clean And De-Grease Window Frames
After the sealant remover has done its job. It’s now time to completely clean the area.
Take your retractable scraper blade and repeat step two. This will scrape all the dissolved sealant skin away from the surface.
You now need to wipe away the mushy sealant skin from the joints using a clean, dry cloth, ensuring the area is dry and free from any residue.
Now, run your finger along the joint to feel for any areas you may have missed.
If there’s still some sealant skin in the joints repeat steps 2 and 3 to ensure every bit of sealant has been removed.
Using the methylated spirit and a cloth, wipe over the frame to ensure it's clean and dry.
This step is crucial as any dirt or water on the frame could effect the silicones ability to bond.
Step 4) Apply Masking Tape Around Window
Carefully stick your tape around the edge of both the window frame and wall either side of the joint you want to seal.
This will ensure a nice, straight, neat finish on the sealant. Also it will stop and silicone smearing into the brickwork around the edge of the window.
Tip: Sometimes masking tape won't stick properly to the surrounding brickwork, especially if its a damp, cold day. In this instance, use strong duct tape.
DO NOT use the duct tape on the window frame itself. It will be a real pain to remove. Only use it on the surrounding brickwork.
Step 5) Add Foam Backer Rod (Optional)
If the gap around the window wasn't previously filled with foam or if the gap is over 5-8mm wide. It's a good idea to add a strip of foam backer into the joint.
This will stop you using excessive amounts of silicone. It also adds an extra layer of insulation around the window.
Step 6) Prepare The Silicone
Using a Stanley knife, remove the top of the cartridge. Add the nozzle to the cartridge's top and trim the end at a slant (roughly a 45 degree angle).
For optimal results, match the size of the opening of the nozzle to the size of the joint you intend to seal. Insert the cartridge into the gun and squeeze until sealant starts to appear out of the tip of the nozzle.
Step 7) Apply Sealant Around Window
With the gun at a 45-degree angle, gently squeeze the trigger and move it steadily around the perimeter of the window. Apply a continuous bead of sealant, ensuring full coverage. Use a consistent speed to maintain an even line.
Important Tip: Only seal down both sides and along the top of the window. Do not seal along the bottom of the window where it meets the window sill.
The small gap along the bottom of the window allows moisture behind the window to escape. If you seal this joint it will cause moisture build up inside the frame causing costly problems down the road, such as mould.
Step 8) Smooth Sealant And Remove Masking Tape
After applying the sealant, spray the bead with the soapy water, this stops the sealant from smearing or sticking to stuff it shouldn't when tooling. Then use a silicone tool to smooth and shape the bead.
This ensures an even, professional-looking finish.
DO NOT lick your finger and smooth the sealant. The bacteria in your mouth can transfer to the sealant and cause premature mould growth. Also, it's disgusting!
Once tooled, remove the tape immediately.
To smooth out any imperfections in the sealant bead once the tapes removed, spray both the silicone and your finger with the soapy solution. Then lightly caress the sealant until you are happy with the finish.
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