How to seal drafty windows with weatherstripping

A draughty window can make a room uncomfortable, increase heating and cooling costs, and allow dust, insects and outside noise indoors. The usual cause is a worn seal around a moving sash, a gap between the frame and wall, or a window that no longer closes tightly.

Weatherstripping is a practical way to improve the seal without replacing the entire window. The materials are available through Australian hardware retailers such as Bunnings, and many types can be installed with basic tools. The best product depends on the window design, the size of the gap and whether the surface is exposed to sun or moisture.

This repair is especially useful in homes in Melbourne, Canberra and inland New South Wales, where winter chills can be noticeable. In Brisbane, Darwin and other humid areas, a sound seal can also help limit wind-driven rain, dust and insects while keeping conditioned air inside.

Before starting, identify where air is entering and check whether the window frame is damaged. Weatherstripping cannot correct rotten timber, cracked glass, severe movement or a sash that is out of square. A small inspection first will prevent you from covering up a larger maintenance problem.

Find the source of the draught

Close the window and inspect the perimeter from inside the room. On a windy day, hold a thin strip of tissue near the frame and watch for movement. You can also feel for cool air with the back of your hand, although moving curtains and uneven indoor temperatures can make this less precise.

Check the meeting rail where two sliding sashes overlap, the corners of casement windows, and the hinge side of hinged units. Look for flattened rubber, brittle foam, gaps in old adhesive and sections that have peeled away. If the draught appears around the fixed frame rather than the opening section, the issue may be failed caulking or a gap in the installation.

Inspect the exterior as well, particularly after heavy rain. Water marks, peeling paint or damp timber may indicate a sealing or drainage problem rather than a simple air leak. Never block drainage holes in aluminium or uPVC frames, as these openings allow condensation and rainwater to escape.

Choose a suitable weatherstrip

Foam tape is inexpensive and easy to apply, making it suitable for small, even gaps around timber or metal windows. It compresses when the window closes, but it may deteriorate quickly in strong Australian sunlight. Choose a product rated for exterior or high-UV use when the strip will be exposed.

Rubber or silicone gaskets generally last longer and cope better with temperature changes. V-strip, also called tension seal, is useful in narrow gaps around sliding windows, while brush seals can reduce dust and insects on larger sliding tracks. For hinged windows, adhesive-backed rubber seals or screw-fixed compression seals are usually more appropriate.

Measure the gap with the window closed and select a strip thick enough to compress without preventing the lock from engaging. A seal that is too thick can distort the frame, leave the window partly open or place pressure on the hinges. If the gap changes considerably along the frame, repair or adjust the window before fitting a flexible seal.

Prepare the frame carefully

Remove old weatherstripping with a plastic scraper or blunt putty knife. Adhesive residue can often be softened with a small amount of isopropyl alcohol, but test any cleaner on an inconspicuous area first. Avoid flooding timber or allowing solvent to contact painted surfaces for longer than necessary.

Clean the frame with mild detergent and water, then let it dry completely. Dust, grease and moisture will weaken the adhesive. For timber windows, lightly sand rough raised fibres and touch up bare areas with suitable primer or paint before installing the seal.

While preparing the area, clear dirt from tracks and drainage channels. If the window is difficult to close because of grit, avoid forcing it against the new strip. A clean track often improves the fit immediately, just as natural sink cleaning can clear household blockages without harsh chemicals.

Install the strip without gaps

Cut each piece slightly longer than the frame section and trim it after positioning. Apply one continuous length where possible, beginning at a corner and pressing the strip down gradually. Do not stretch adhesive-backed foam or rubber as you install it, because it can shrink later and leave gaps at the corners.

Place the seal where the closed window will compress it, not where it will be scraped off as the sash moves. On a casement window, this is normally the inner stop or the face of the frame. On a sliding window, fit the strip along the contact edge while keeping the rollers and drainage openings clear.

Join corners neatly rather than piling several layers together. Close and open the window several times to check for binding. The lock should operate with normal pressure, and the sash should sit evenly against the seal around its full perimeter.

Deal with common window types

Timber double-hung windows often need seals along the meeting rails and side channels. Flexible V-strip can work well in these locations, but the channel must be clean and the sash must still move freely. Older timber frames may also need minor adjustment or fresh glazing putty if the glass is loose.

Sliding aluminium windows commonly lose efficiency at the interlocking centre section and along worn pile seals. Replace damaged brush pile with a matching profile, taking the old piece to the hardware shop when possible. Do not seal over weep holes or fill the running track with adhesive.

For awning and casement windows, compression seals provide a firm barrier when the handle pulls the sash against the frame. If the handle feels loose or the sash sits unevenly, tightening hardware may be more effective than adding thicker weatherstripping. Bay windows and unusual imported systems may require a specialist profile that is not stocked in every Australian store.

Improve the seal around the whole opening

If air still enters after the moving parts are sealed, examine the joint between the window frame and the wall. Small exterior cracks can often be sealed with paintable acrylic or a flexible exterior-grade sealant, provided the joint is dry and sound. Use a product suited to the frame material and local exposure.

A wide gap, soft timber or visible movement should be investigated before caulking. Expanding foam can distort a frame when used carelessly, and it should not cover drainage paths. For larger gaps around an older installation, backer rod and appropriate sealant may produce a more durable result than repeated layers of tape.

Moisture management matters as much as draught control. In homes affected by storms or high groundwater, routine checks such as sump pump maintenance can help reduce damp conditions that contribute to swelling timber, mould and failing seals.

Test the finished repair

After installation, check the window on a windy day and repeat the tissue test at each corner. Look for daylight around the closed sash, listen for whistling and feel whether the indoor surface is less cold. A thermal camera can reveal cold spots, but it is not essential for a basic home inspection.

Watch the seal over the next few weeks. If it peels, it may have been installed on a dirty or damp surface. If it becomes crushed quickly, the strip may be too thick or the frame may be misaligned. In coastal areas such as Perth, Sydney and the Gold Coast, salt air can accelerate corrosion and degrade exposed materials, so wipe frames and tracks periodically with clean water.

Keep nearby garden growth trimmed so branches do not rub against screens or window frames. Good yard maintenance, including choosing the right compost bin, can also help limit odours and pest activity near openings. In rental properties, record the repair and report damaged frames or failed glazing to the property manager before making permanent changes.

A properly fitted seal should make the window close firmly without excessive force. Clean the frame, measure the gap, select a weather-resistant profile and install it in a continuous, uncompressed line. Testing the result and keeping drainage paths clear will provide a more comfortable, efficient window through Australia’s changing seasons.