A cold line around the edge of a window, a curtain that moves when the window is shut, or a room that never seems to warm up are all familiar signs of a draught. Learning how to fix draughty windows can make a noticeable difference to comfort, heating costs and the overall feel of your home – especially in older London properties where original windows may have gaps around the frame.
The right repair depends on where the air is getting in. A small gap around a sash window can often be sealed quickly, while a damaged hinge, failed glazed unit or rotten timber frame needs a more considered repair. Start by locating the source rather than covering up the symptoms.
How to fix draughty windows: find where air is entering
Choose a cool or windy day, close the window securely and run your hand slowly around the frame. Pay attention to the top and bottom corners, the opening edge, the meeting point between two sashes, and where the frame meets the wall. You may feel a clear flow of cold air, but a thin piece of tissue held nearby can also reveal movement.
Look for visible clues too. Cracked sealant, flattened rubber seals, daylight around the frame, loose handles and gaps beneath a window board all point towards a likely cause. Do not assume every cold area is a draught. Single glazing and older double glazing can feel cold to the touch even when the window is properly sealed.
If you notice damp patches, mould, staining or a persistent musty smell around the window, the issue may involve water ingress as well as air leaks. That calls for a proper inspection before adding sealant, as trapped moisture can make timber decay and internal finishes worse.
Check the simplest fixes first
Many draughts come from worn, missing or poorly fitted seals. These are straightforward to replace, provided you choose the correct type and the window can still close without force.
Replace worn window seals
Modern uPVC and aluminium windows commonly use rubber or foam seals fitted into grooves around the opening section. Over time, these can shrink, flatten or come away from the frame. Carefully remove a short section to identify its shape before buying a replacement. A seal that is too thick may stop the window closing properly, while one that is too thin will not seal the gap.
Clean the groove and surrounding frame first, then fit the replacement seal evenly without stretching it. Test the handle and locking points afterwards. The window should close firmly but not need excessive pressure.
For older timber casement or sash windows, self-adhesive foam, brush or rubber draught strips can work well. Brush strips are often a good choice for sliding sash windows because they allow movement while reducing the gap. Foam strips are inexpensive and useful for small, even gaps, but they generally wear more quickly than quality rubber seals.
Seal small gaps around the frame
If air is coming through the joint between the frame and the internal wall, remove any loose or failed sealant and clean the area thoroughly. Apply a suitable flexible decorator’s caulk or sealant for small internal gaps, then smooth it neatly. Once dry, it can usually be painted to match the surrounding finish.
External gaps require an exterior-grade, weatherproof sealant. This work needs care: sealing the wrong area can block drainage channels on certain window systems, allowing water to collect where it should be able to escape. If you are unsure whether a gap is part of the frame’s drainage design, ask a professional before applying anything.
Adjust loose handles, hinges and locks
A window that does not pull tightly against its seals will often let in a draught, even when the seals themselves look fine. On uPVC casement windows, worn hinges can cause the opening section to drop slightly, creating a gap on the hinge side or along the top. Loose handles and faulty locking mechanisms can have the same effect.
Minor adjustment may be possible, but forcing screws or altering hinge settings without knowing the mechanism can make alignment worse. If the window catches, will not lock, or has visibly dropped, a window repair is usually more reliable than repeatedly adding thicker seals.
Treat timber windows with care
Original timber windows bring character to period homes, but they need regular attention to stay weather-tight. Peeling paint, open joints and soft areas of wood are not simply cosmetic problems. They can let in cold air and rain, eventually leading to more extensive damage.
Small cracks and open joints can be repaired, filled and repainted once the timber is dry and sound. Larger areas of decay may need sections of timber repaired or replaced before the window can be sealed effectively. Painting over rotten wood or applying fresh sealant to a damp frame is only a short-term cover-up.
Sash windows also need to move freely. Painting them shut may appear to stop a draught, but it prevents ventilation and makes future maintenance harder. Purpose-fitted draught-proofing can improve comfort while allowing the sashes to open and close as intended.
When glazing is the real problem
If a double-glazed window has misting between the panes, the sealed unit has failed. This is not normally an air draught in the same way as a gap around the frame, but it reduces insulation and can make the room feel colder. Replacing the glazed unit may be enough if the frame is still in good condition.
Cracked glass, loose beading or panes that move within the frame should be dealt with promptly. Aside from heat loss, damaged glazing can become a security and safety issue. Avoid temporary tape repairs except as a very short-term measure while arranging a proper repair.
For single-glazed windows that are otherwise in good order, secondary glazing can be worth considering. It can reduce heat loss and outside noise without replacing original windows, which may be particularly useful in conservation areas. The trade-off is cost, appearance and the need for a suitable installation, so it is best considered as part of a wider plan for the room.
Avoid common draught-proofing mistakes
Trying to seal every opening can create new problems. Windows provide ventilation, and some homes rely on trickle vents or designed ventilation gaps to control condensation. Do not block trickle vents, air bricks or drainage holes in the frame. These features may feel counterproductive on a cold day, but they help manage moisture and protect the property over time.
Expanding foam should also be used with caution. It is difficult to control, can look untidy around finished frames and is not a suitable substitute for repairing a loose or damaged window. Likewise, thick adhesive strips may temporarily stop a draught but can prevent the window from shutting or pull paint away when removed.
For tenants, check your tenancy agreement before making permanent changes. Simple temporary draught strips may be acceptable, but repairs to glazing, frames and external sealant are usually a landlord’s responsibility. Take clear photos of the problem and report it early, particularly if there is damp or water coming in.
When to arrange a professional repair
A professional repair is sensible when the draught is linked to failed hinges, broken locks, loose frames, rotten timber, damaged glazing or signs of water ingress. It is also the right choice if you have tried new seals and the problem remains. Air may be entering behind internal trim, through a poorly fitted frame, or from a nearby wall defect rather than the window itself.
For busy households and landlords, having one reliable team assess the issue can save time and avoid unnecessary work. Handy House can help with practical window repairs, sealing, timber maintenance and making good surrounding internal finishes, with careful workmanship and clear advice on what the property actually needs.
A well-sealed window should still open, lock and ventilate properly. If yours does not, arranging a repair now can make the next cold spell far more comfortable.