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Can I change windows in a protected structure?

Window replacement in a protected structure normally requires planning permission because it materially affects character. Repair of existing joinery, draught-proofing and secondary glazing are usually preferred and often accepted without replacement.

Historic glass and joinery are part of what is protected. Conservation officers generally look for repair of existing sashes, replacement of decayed sections rather than whole frames, and reinstatement of missing glazing bars.

Where performance is the concern, draught-proofing an existing sash and adding slim secondary glazing can deliver most of the comfort benefit while keeping the original window.

Usually acceptable measures

  • Splice repair of decayed timber sections
  • Brush-pile draught-proofing to sashes
  • Secondary glazing set behind the original window
  • Insulated shutters or heavy curtains

Sources

Last reviewed 28 August 2026. General information only — not legal or planning advice.

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