Listed building windows

The law protects listed building windows as part of the building’s character, so you need listed building consent from the council before replacing or significantly altering them, inside or out. Doing the work without consent is a criminal offence. In practice, councils usually expect original windows to be repaired rather than replaced, and secondary glazing is the most common way to make them warmer and quieter.

When listed building windows need consent

The Planning Portal is clear that listed buildings need consent for any significant works, internal or external. Replacing windows, changing glazing bars, swapping single for double glazing or changing the colour all usually count. Even like-for-like replacement often needs consent, because the old glass and joinery may be part of what is protected.

Small repairs that don’t change the character, such as easing a sticking sash or replacing a broken pane to match, are usually fine. However, ask the conservation officer if you’re unsure. The answer costs nothing, and the penalty for getting it wrong, under the listed buildings law, can include a fine or prison.

Repair first

A good joiner can keep an old timber window going almost indefinitely. They splice in new timber, re-cord sashes, reglaze in matching glass and fit draught-proofing, and the window carries on for decades. As a result, councils start from repair, and a well-repaired window with good draught-proofing is warmer than most people expect.

Making listed building windows warmer

• Draught-proofing. Brush or rubber seals fitted into the sashes make the biggest difference for the least money.
• Secondary glazing. A slim second window fitted inside the original. It’s reversible and leaves the old window untouched, so consent is often straightforward. See secondary glazing, which typically costs £280 per window.
• Shutters and heavy curtains. Many period houses had working shutters; bringing them back into use helps at night.
• Slim double glazing. Some councils accept thin double glazed units in new or existing timber sashes, especially on rear elevations. It always needs consent.

Conservation areas are different

A house in a conservation area isn’t necessarily listed. Normal permitted development may still apply, unless an Article 4 direction removes it. See planning permission for windows for the rules there.

Applying for consent

Speak to the conservation officer early, then apply with drawings and photographs of the existing windows, and details of what you propose. Use a joiner or installer who has done listed work before, and ask them for photographs of similar jobs. When you’re ready, get quotes for timber windows or secondary glazing, and compare them carefully.