DIY Sash Window Draught Proofing

Traditional sliding sashes need running clearance, but excessive gaps create draughts and rattling.

Find the draught

Inspect the meeting rails, staff beads, parting beads and the junction between case and masonry. Check that the window closes fully before choosing seals.

Choose suitable materials

Brush seals and replacement beads can work well when correctly sized. Over-thick seals may make the sash stick. In protected buildings, check whether proposed alterations need consent.

Find the air path

Draughts commonly enter at the meeting rails, staff beads, parting beads and the junction between the case and masonry. A poorly closing fastener can leave a gap that a new seal alone will not correct.

Assess before fitting seals

Check for loose joints, rotten sills, sticking sashes and failed putty. Repair these defects first. Draught proofing should not conceal water ingress or prevent the sash moving freely.

Brush seals and beads

Purpose-made beads with brush seals can reduce air leakage while accommodating sliding movement. Seal size, pile density and the existing clearances must be selected for the particular window.

Ventilation matters

Reducing uncontrolled draughts may change background ventilation. Consider condensation, room ventilation and any combustion appliance requirements rather than sealing every opening indiscriminately.

Listed buildings and appearance

On historic or protected buildings, discreet and reversible methods are preferable. Confirm whether consent is needed before altering significant fabric or appearance.

Check the finished result

Test both sashes through their full travel, check the fastener and inspect for pinched seals. A good result should reduce draughts without introducing excessive friction.