Sash windows in listed buildings & conservation areas
What you can repair without consent, what needs permission, and what conservation officers in Kent and London actually accept.
Repairing a sash window in a listed building or conservation area is almost always acceptable, and almost always preferred — it is replacement and changes to glazing that need consent. We work on listed and conservation properties across Kent and London every week, and we will tell you where you stand before anything is agreed.
What is normally fine without consent
- Repairing rotten timber in sills, rails, stiles and horns with new timber
- Replacing broken sash cords, pulleys and weights
- Freeing a window that has been painted shut
- Concealed draught-proofing, where the seals are routed into the sash
- Re-puttying and re-glazing with matching glass
- Redecorating in an appropriate paint system
What normally needs consent
- Replacing a window, even like-for-like, in a listed building
- Any change to glazing — slim double glazed units included
- Changing timber type, sightlines, horn profile or glazing bar widths
- Changing the opening, or fitting a different style of window
- Secondary glazing in some authorities, though it is usually accepted
How to get it right
Email your conservation officer with photographs of the window and a description of the work before you commit to anything. Most will answer informally and quickly, and an informal yes in writing is worth a great deal if a neighbour complains later. We supply the specification and the detail you need for that email, and for a full application if one is required.
Where a window is genuinely beyond repair, a made-to-measure replacement copied from the original is what gets approved — see our replacement sash windows page, or repair or replace for how we judge it.
Listed building questions
Do I need consent to repair a sash window in a listed building?
Like-for-like repair normally does not need listed building consent, because nothing about the building changes. Altering the window — new glazing, different material, changed sightlines — does. Ask your conservation officer in writing; it is free and it takes one email.
Can I put double glazing in a listed sash window?
Sometimes, and only with consent. Slim units are accepted by some authorities and refused by others. Secondary glazing is the route that is almost always acceptable, because the original window is untouched.
What about a conservation area rather than a listed building?
Repairs are fine. Replacement may need planning permission where an Article 4 direction removes the usual permitted development rights, which is common in Kent’s town centres.
Will you supply what I need for an application?
Yes. We provide the written specification, the timber and glazing detail and photographs of the existing window, which is normally what a conservation officer asks for.