How to Stop Draughts Around Windows Properly

A cold line of air around a window is more than an inconvenience. It can make rooms harder to heat, encourage condensation and point to failing seals or defects around the frame. Knowing how to stop draughts around windows starts with identifying where the air is entering. The right repair depends on whether the issue is the opening sash, the perimeter seal, the surrounding wall or the window itself.

Find the source before applying sealant

Draughts are often blamed on the glass, but glass is rarely the problem. Air normally enters through gaps between the opening section and the frame, failed perimeter sealant, loose trims, worn hinges or gaps in the surrounding masonry.

On a still day, run your hand slowly around the internal edge of the window frame. You may feel a clear change in temperature or moving air. A thin strip of tissue held near suspected gaps can also reveal airflow. Check the corners carefully, along the sill, around trickle vents and where internal linings meet the frame.

Then inspect the outside. Look for cracked, shrunken or detached sealant around the frame, especially at lower corners and on elevations exposed to driving rain. Sealant that has pulled away from either surface no longer provides a reliable weather seal. Discolouration, mould around internal reveals or staining below the window can suggest that water is entering as well as air.

The distinction matters. A small gap around an opening casement may need replacement weatherstrip. A failed external perimeter joint needs proper removal and resealing. Covering either issue with a quick bead in the wrong place may trap moisture, obstruct drainage or simply fail within a short period.

How to stop draughts around windows: match the repair to the fault

Replace worn weatherstripping

Weatherstripping seals the moving parts of a window when it is closed. It is common on casement, sash and tilt-and-turn windows, and it gradually compresses, flattens or tears with age. If the window closes but still allows air through its edges, this is usually the first area to inspect.

Choose a profile designed for the type of frame and gap. Self-adhesive foam strips can be suitable as a short-term domestic improvement, but they are not always durable enough for heavily used windows or exposed locations. Rubber or purpose-made compression seals generally offer a better long-term result when correctly fitted.

The surface must be clean, dry and free from old adhesive before fitting. Do not use a thick strip simply because the gap feels large. Excess material can prevent the window from closing fully, put pressure on hinges and create another route for rainwater. If a window only seals when forced shut, the problem may be adjustment rather than the seal itself.

Adjust the hinges, locks or sash

Modern uPVC and aluminium windows rely on the sash pulling tightly against compression seals. Over time, hinges can wear, locking points can move out of alignment and the sash can drop slightly. The result is a visible gap or a poor seal on one side, even where the weatherstrip looks sound.

Check whether the window sits squarely in its frame when closed. Difficulty locking, rubbing at one corner or a larger gap along the hinge side are signs that adjustment or hardware repair may be required. Minor adjustments can be straightforward for a competent person, but overtightening locking mechanisms or altering hinges without understanding the system can damage the hardware.

Timber windows need a different approach. Seasonal movement, paint build-up and worn catches can stop the sash seating properly. Draught-proofing strips can work well, but the timber should first be checked for rot, loose glazing putty and failed paintwork. A seal is only as good as the surface it is fixed to.

Reseal the outside perimeter correctly

The external joint between a window frame and the wall is one of the most important weatherproofing details on the building. It must accommodate minor movement, resist rain and maintain adhesion to both surfaces. When this joint fails, cold air and water can pass behind the frame and into the internal reveal.

A durable repair is not achieved by applying fresh sealant over cracked material. The failed sealant should be carefully cut out, the joint cleaned and the surfaces prepared. Any damaged backing material, loose render or decayed timber needs attention before a new joint is formed.

The correct sealant type depends on the frame material, substrate, joint width and exposure. Professional-grade low-modulus silicone is commonly used for external window perimeter sealing because it remains flexible and performs well in wet, exposed conditions. However, silicone is not appropriate for every surface or every joint. Compatibility with coated aluminium, painted surfaces, porous masonry and existing materials must be considered.

Good application is as important as product choice. The joint should have consistent depth and shape, with a clean finish that sheds water rather than holding it. Sealant applied to wet, dusty or unstable surfaces is likely to lose adhesion early. For upper-floor windows, awkward access or extensive defects, professional application is the safer and more dependable option.

Seal internal gaps with care

Internal gaps around a window can allow draughts through finishes even when the outer weather seal is intact. These may appear where plaster meets the frame, behind loose architraves or around internal boards. Filling these gaps can improve comfort and reduce air leakage.

Use a suitable internal decorator's caulk or flexible sealant where the joint is dry and intended to be painted. Avoid assuming that an internal seal alone solves an external weatherproofing failure. It may reduce the draught temporarily while allowing rainwater to remain within the construction.

Internal sealing should not block designed drainage routes in the window frame. Most modern frames include drainage and ventilation details that must remain clear. If you are unsure where water is intended to escape, stop before sealing and have the installation assessed.

Do not overlook surrounding building defects

Not every draught comes through the window installation itself. Gaps in external render, open mortar joints, failed cladding seals and cracks around the sill can direct cold air into the wall cavity or reveal. Bay windows, older properties and extensions are particularly prone to movement at junctions between different materials.

Look for gaps where the sill meets brickwork, cracks at the top corners of openings and deteriorated mastic seals around external trims. In commercial premises, repeated movement, façade exposure and large window systems can make isolated patch repairs unsuitable. A wider inspection may be needed to identify failed joints across an elevation before water ingress affects insulation, finishes or operations inside.

Condensation should also be separated from draught-related damp. Condensation forms when warm indoor air meets a cold surface, often because of high humidity and insufficient ventilation. A draught can make that surface colder, but resealing alone will not resolve persistent condensation caused by drying clothes indoors, inadequate extraction or blocked vents. The correct solution may involve both improved sealing and controlled ventilation.

When a simple repair is not enough

Call for professional assessment if there is visible water ingress, soft or damaged timber, loose frames, failed double-glazed units, extensive perimeter cracking or signs of movement in the wall around the opening. These conditions need more than a tube of sealant.

The same applies where access is difficult or where window sealing forms part of wider façade, rooflight or expansion-joint work. A clean, correctly prepared seal protects the building envelope and gives a finish that lasts. Rushed repairs often fail at the edges first, leaving the property exposed again when the weather turns.

For homeowners, facilities managers and contractors, the most reliable approach is to treat window draughts as a building maintenance issue rather than a cosmetic annoyance. Check the moving seal, inspect the external joint and deal with defects before they become water damage. A properly sealed window should close comfortably, keep out wind and rain, and help the room retain the warmth you are paying for.