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How to Fit our Sash Window Gap Seal

Gapseal is perfect to fill the gaps around your sash windows. Its unique design and the application tool ensure that your gaps can be sealed without causing damage to the window or frame. It is designed to address difficult gaps of varying thickness and in areas where windows either cannot be opened or have to slide up and down within a frame.

Step 1 - Preparation

Before fitting Gapseal ensure that gap between the window and the frame is clean and free from dirt and debris which can be removed using the applicator provided or an appropriate tool such as an old credit card or a screwdriver.

When removing debris from between floorboards, care should be taken to avoid injury from old damaged windows and frames.

Step 2 - Starting the Application

Using the applicator provided push the end of the Gapseal into the gap at the end of the window frame.

To make the first part of the installation easier the end of the Gapseal strip can be carefully trimmed into a point using a pair of scissors, this will allow the end of the seal to be pushed into the window gap easily.

Step 3 - Fitting the Seal

Stretch the windows seal as much as necessary to fit into the gap without excessive force. The resistance to the applicator should be comfortable.

Work a short section at a time! Repeat this process over the length of the window gap. The ideal depth is 2-3 mm below the surface of the window frame.

Step 4 - Cutting to Size

After you have fitted Gapseal to the full window and are reaching the end of the gap, the final length of the gap should be measured and the sealant trimmed with about one inch surplus length.

This is done to ensure a good fit during the final stage of installation and to prevent gaps being created at a later stage. Gapseal can easily be cut to size with household scissors.

Step 5 - Finishing the Application

Once Gapseal has been trimmed to size, use applicator or an appropriate tool such as an old credit card or a screwdriver to push the sealant into the remaining window gap.

This will ensure a snug fit and create an effective seal between the window and the frame. This method should be applied to each window you would like to seal.

Safety Tip - Avoid Injury Risks

The application tool is extremely effective for installing the sash window sealant becasue of its specially designed shape.

It is however important to remember that excessive force or using the tool not as intended can result in injury. Never work the applicator towards your face. The applicator should be stored in a safe place away from children.

Important: When installing Gapseal in rooms with open fires or a gas fire, please ensure that a sufficient flow of air to the fire remains. Without sufficient air flow there is a risk of carbon monoxide poisoning. You can increase air flow to the fire without cooling down the room by installing shuttable air inlets in the floor directly next to the fire.

Our Customers Love Gapseal

4.5 / 5 Stars

Read reviews from 96 customers who've installed Gapseal to eliminate draughty windows and make their homes warmer.

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Gapseal 10m Pack

Suitable for 2 - 7mm gaps

13.99 inc VAT

11.66 ex VAT

Additional Application Tool

Do I need another applicator?

2.29 inc VAT

1.91 ex VAT

Sub Total:

£0.00 inc VAT

£0.00 ex VAT

FREE Standard Delivery

All UK orders are shipped FREE of charge and delivered in 2-3 working days by Royal Mail as standard.

Please Note: Deliveries to Islands and remote locations can take an additional 1-2 days to be delivered.

Next Day Delivery

Orders can be upgraded to next working day delivery for
£4.50 inc VAT and will be delivered by UK Mail.

For delivery on order within the next
and choose next working day delivery.

International Delivery

We offer an international shipping service for customers looking to buy Gapseal from outside of the UK.

If you are intersetd in an internatinal delivery please contact our international sales team for a shipping quote.

Image Gallery

An excellent collection of images showing sash window gaps that have been sealed using Gapseal sash window gap filler.

See Full Image Gallery