Are you in a conservation area? Are you already filled with dread at the idea of months of correspondence with your local council just to upgrade your windows? You’re not alone. Different councils give different answers, and the process can feel overwhelming.
The good news is that we can manage everything for you from beginning to approval. We’ve successfully achieved planning permission for hundreds of clients in conservation areas for the installation of new timber windows – skip the hassle completely and let Wandsworth Sash Windows do the entire planning application for you.
What is a conservation area and why might planning permission be required?
A conservation area is a building or area designated by the local council as having special architectural or historical significance. Since windows form a large part of a building’s appearance, they are a key feature councils aim to preserve. This is why, in many conservation areas, you may need planning permission to install new windows – authorities want to protect the look and feel of the street.
Do I need planning permission to change my windows in a conservation area?
This is where things get complicated! There is no single answer because every London borough has its own rules.
To illustrate how inconsistent the guidance can be, we contacted three London councils with the same question: Do I need planning permission to upgrade my windows in a conservation area? We received three completely different answers:
- Lambeth Council – They said they do not provide informal advice and recommended submitting a paid pre‑planning application. The cost? £928.00 – more than an actual planning application for windows!
- Lewisham Council – They pointed us to a document explaining what types of windows are acceptable: same material, same type, same design. Helpful, but it didn’t clarify whether permission was required.
- Hammersmith & Fulham Council – They stated that replacing windows in a single dwelling house usually does not need planning permission unless you are changing the frame material (e.g., timber to uPVC). A rare, clear answer!
One rule is consistent across the UK: if you live in a flat, you will definitely need planning permission. Flats do not have permitted development rights, so any external change affects the whole building.
If this already feels too confusing, let Wandsworth Sash Windows take care of it for you.
General guidelines for replacement windows in a conservation area
Even though councils differ on when planning permission is required, they generally agree on the key criteria for acceptable window replacements:
- Use the same material – This is almost always timber in historic streets.
- Follow the same design – If your original sash has a curved top and two glazing bars, your replacement must match exactly.
- Do not change the opening size – Enlarging or reducing window openings almost always requires permission.
If you follow these points when planning conservation area replacement windows, you are unlikely to run into issues.
If you’d like to learn more about what documents are required for a planning application, visit the relevant section on our website.
How do I know if I am in a conservation area?
Finding out requires a little online detective work:
- Search for conservation areas on your local council’s website.
- Use the council’s interactive map to locate your property.
- Look for your specific conservation area’s “appraisal” document – these often explain the architectural history of your street and why its features (including windows) must be preserved.
A word of caution: please don’t rely on AI tools to check if your property is in a conservation area. We’ve tested them – they often give incorrect results.
What happens if I replace my windows without permission?
Replacing windows without the required permission is considered a breach of planning control, but it isn’t a criminal offence at first. Councils usually try to resolve the situation rather than punish:
- You may be asked to submit a retrospective planning application.
- If the new windows meet conservation guidelines, the issue ends there.
- If they don’t, the council may issue a Planning Enforcement Notice, requiring you to:
- Remove the unauthorised windows
- Install compliant replacements
- Complete the changes within a set timeframe (often 2–6 months)
Failure to comply becomes a criminal offence, with fines of up to £20,000. Fortunately, as long as you communicate with the council, things normally do not escalate that far.
My neighbours have uPVC windows – how did they get away with that?
A few explanations:
- They may have replaced their windows before the area became a conservation area or before an Article 4 Direction was introduced.
- They may simply have taken a chance and installed windows without applying.
- They may have received permission years ago under different rules.
Unfortunately, this does not set a precedent – your application will always be assessed under current policies.
Has Wandsworth Sash Windows replaced windows in conservation areas?
Absolutely. We have replaced hundreds of windows in conservation areas and completed more than 100 successful planning permission applications for windows. Here are three examples:
Fawcett Street, Chelsea SW10
Completed October 2025. We installed four pairs of new sashes to a first‑floor frontage within the Boltons Conservation Area. The planning application was submitted on 16th May and approved early on 30th June – well ahead of the official target date.
West Hill, Putney SW15
Completed October 2025 to a first‑floor flat in the West Putney Conservation Area. We installed a new 5‑part casement bay and several new sash replacements. Because this was part of a larger renovation, our full planning service gave the client peace of mind.
Wickham Road, Brockley SE4
Installed October 2024. We fitted eight new pairs of sashes into existing box frames. The planning application was submitted on 24th June and approved just over 8 weeks later on 20th August.
Let Wandsworth Sash Windows handle the entire process
We can make the entire process of applying for planning permission for windows in conservation area stress‑free, whether you’re:
- changing windows in a conservation area,
- replacing windows in a conservation area flat,
- or seeking clarity on conservation area consent for replacement windows.
From interpreting council guidelines to preparing all drawings and managing communication with planning officers, we’ll ensure your proposal aligns with heritage requirements and moves smoothly through approval.
If you’re looking to begin the process or simply want expert guidance, get in touch with Wandsworth Sash Windows today.