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Repair and restoration

Sash and timber window repair

Sash window repair keeps original box sash windows working rather than replacing them, which in a conservation area or a listed building is often the only option. Refurbishing one window typically costs £350 to £750, against several times that to replace it.

A box sash window with the stile opened to show the pulley, cord and weight

What this covers

What it costs. Refurbishing a box sash window costs £350 to £750 per window, including new cords, draught proofing and localised rot repair. Full cost breakdown.

What the job covers

  • Cord and weight replacement
  • Draught proofing and re-balancing
  • Splicing out rot
  • New box sash manufacture
  • Secondary glazing

What is involved

A box sash runs on cords over pulleys with cast iron weights hidden in the box on each side. The usual failures are broken cords, painted-shut sashes, worn staff beads, and rot at the bottom rail and the sill where water sits. A full refurbishment takes the sashes out, replaces the cords and re-balances the weights to the sash, splices out any rot with matching timber, re-beads, and fits brush draught seals in the running surfaces.

Draught proofing is the reason most people call. A properly sealed sash window loses much of its reputation for cold and rattle, and the work is reversible, which matters for listed consent. Where the glass is the problem rather than the frame, slim double-glazed units can sometimes be fitted into the existing sashes, though the sash may need deepening and the weights re-balanced to carry the extra load.

Box sash windows in the facade of an older building

Cord and weight replacement, one of the jobs under sash windows.

Choosing someone for the job

Ask whether they splice rot out or fill it, since filler in a sill is a two-year fix. Ask whether the weights are re-balanced after any change to the sash. In a listed building, ask what they have done before that needed consent.

Related jobs:

Common questions

Is repairing a sash window cheaper than replacing it?

Almost always, and in a listed building or conservation area replacement may not be permitted at all. Refurbishment also keeps the original glass, which is part of the character.

Can sash windows be draught proofed?

Yes. Brush seals in the running surfaces and the meeting rail cut draughts and rattle substantially, and the work is reversible.

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