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Applying for planning permission is a mundane but vital part of undertaking a home improvement project. It is not a stage that should be skipped, especially if a project falls outside of permitted development. If you have saved up enough to invest in new windows, doors, an extension, or renovation, you will want things to go smoothly so you can enjoy the fruits of your labour. To avoid the disappointment of a rejected application, not to mention the waste of time and money associated with one, you will need to ensure your project is set up for planning approval.
Unfortunately, gaining planning permission is not as straightforward as it may initially seem. There are no fixed rules about what is and what is not allowed and gaining approval will vary from council to council. It may also depend on where you live and what you want to change or develop.
What is planning permission?
Planning permission is formal approval from your local planning authority that confirms proposed building work is acceptable in principle. It helps make sure changes suit the area, follow local policy, and do not create avoidable problems for neighbours or the wider streetscape.
For window projects, the key point is simple: permission is about how the outside of your home looks and how it affects the character of the area (separate from building regulations, which focus on safety and performance). Like-for-like replacements on many houses can come under permitted development, but permission is less likely if you’re changing the look, creating a new opening, or your property has extra restrictions.
What is permitted development?
You can perform certain types of work without needing to apply for planning permission. These are called “permitted development rights”. They derive from a general planning permission granted not by the local authority but by Government. It is also important to point out that the permitted development rights which apply to many common projects for houses do not apply to flats, maisonettes, or other buildings. Likewise, commercial properties have different permitted development rights to houses.
In some areas of the country, known as ‘designated areas,’ permitted development rights are more restricted. For example, if you live in:
- A Conservation Area
- An Area of Outstanding Natural Beauty
- A World Heritage Site
You will need to apply for planning permission for certain types of work which do not need an application in other areas.
Our general advice is that you should contact your Local Planning Authority and discuss your proposed project before any work commences. They will inform you of any reason work may not be allowed and if you need to apply for planning permission for all or part of the work. Trust us when we say it is not worth risking starting works without checking, even if you feel certain that your development falls within permitted development rights. Bear in mind that what you can and cannot do will also vary from council to council, so if you own two properties in different areas, works may be granted in one property, but not the other. It is always worth checking first.
Why planning permission matters for windows in a conservation area
If you live in a protected area, small details can have outsized consequences. Planning permission for windows in conservation areas can be more sensitive because councils are trying to protect the consistent “look” of historic streets and buildings.
The main risks for homeowners are wasted time, wasted money, and work that needs to be reversed later. The sections below go into the practicalities and timelines, but the headline is this: if there is any doubt, get certainty before you commit.
If you want more background on how conservation areas work, read our guide on replacing windows in a conservation area.
Why windows trigger planning control more than people expect
Windows sit right on the “public face” of a property, so even a change that feels minor can be treated as visually significant. Planning scrutiny often increases when a project involves things like:
- Changes that are clearly visible from the street (front elevations especially)
- Alterations to proportions, glazing patterns, horns, bars, or frame profiles
- Material changes (for example, timber to a different finish or appearance)
- Creating a new opening rather than replacing what is already there
This is why the question homeowners ask us most often is some version of: do you need planning permission for new windows – and why the safest route is to confirm your position early.
See our conservation area guides
Will you need to seek planning permission for your project? If you live in a conservation area, there are requirements and restrictions you will need to comply with. Our team has successfully submitted hundreds of planning applications and have put together guides for different areas. Learn more about the process you’ll need to follow to obtain planning permission.
Bromley conservation areas – Very large borough with 47 conservation areas that protect a wide range of historic villages, parks and town centres across suburban south-east London.
Camden conservation areas – Roughly half of Camden is designated as conservation areas, reflecting its rich mix of historic estates, parks, and central London townscapes.
Greenwich conservation areas – Home to 23 conservation areas including the UNESCO-recognised Maritime Greenwich, with a focus on preserving world-class heritage and historic settlement patterns.
Hammersmith and Fulham conservation areas – Contains 44 distinct conservation areas covering historic squares, estates and parts of West London, overseen alongside OPDC strategic zones.
Islington conservation areas – With around 41 conservation areas across the borough, Islington’s designations reflect diverse historic architecture and urban character from canal sides to neighbourhood centres.
Kensington conservation areas – One of London’s most heritage-dense boroughs with 35 conservation areas covering high-status historic neighbourhoods and estates.
Southwark conservation areas – A broad range of 50+ conservation areas spanning historic streets, market areas and village cores that anchor this south London borough’s layered urban history.
Wandsworth conservation areas – Wide variety of conservation areas from village remnants to significant estates and parks, reflecting the borough’s architectural diversity.
What planning permission services do we provide?
If you want a clear answer rather than guesswork, we can manage your enquiry end-to-end. That typically means:
Understanding what the council is likely to want,
Preparing the right supporting information, and
Submitting a proposal that is set up for approval – so your installation can move forward with confidence.
Next steps: how to get certainty (without losing weeks)
- Identify what you are changing (like-for-like replacement, altered appearance, or a brand-new opening).
- Confirm your property type and constraints (house vs flat/maisonette, conservation area, listed status, Article 4 direction).
- Treat “probably fine” as a risk – councils can interpret “like for like” differently.
- Get professional support from us if you want it handled properly – especially where heritage constraints apply.
- Only book manufacturing/installation once you have clarity on what’s required.
Contact the Wandsworth Sash Windows team
Speak to our team to find out more about our sash window services. You can call us on 020 3993 3609 or email info@sashwindows.london so that we can discuss your enquiry with you.
FAQs about planning permission in conservation areas
We understand that applying for planning permission takes time and can be a complicated process. Here are some answer to questions that we are typically asked about planning and we would welcome the change to talk to you in person about your project.
Matthew & Nathan Smith
An article 4 direction provides additional planning control in a particular location. It allows the council to remove permitted development rights over some alterations, such as replacement windows and doors, new porches, and exterior painting. It also includes changes of use from an area or property in certain limited situations where it is necessary to protect the local area.
Even though there are more restrictions associated with planning permission for properties within Conservation Areas, Listed Buildings, or properties on designated land, the guidance available on council websites regarding what you can and cannot do in each of these areas can be vague. For example, a council may say “if you are in a conservation area but not in an article 4 and your building is not listed, you can replace your windows as long as they are like for like.”
However, what does ‘’like for like’’ mean? Does it mean simply making sure they look the same and they are made of the same material? Or does it mean if they are currently single glazed, they need to remain as single glazed units? “Like for like” is an ambiguous term which we believe the council uses to encourage you to submit a planning application to ensure correct procedures are followed. Don’t forget, the council benefits financially from each application submitted too.
Similarly, if you have ever called the council to ask for advice, it is highly likely that their advice would be to apply for approval. We cannot stress enough the importance of seeking permission before commencing work. If you conduct work that does not fall within permitted development rights, it could lead to a host of costs further down the line.
Enlist the help of a professional. If you do not have time, or you are worried that you will not be able to manage the planning process confidently, a professional building contractor will be able to do this for you.
At Wandsworth Sash Windows, we have a resolute planning team who manage all our applications and have done a wide array of applications for varying types of works in properties within heritage and conservation areas. We have submitted approximately 300 planning applications to date for projects within conservation areas and, to date, a council has never refused an application we have made.
There is no stress, hassle or chasing involved for the customer, we will manage your entire project for you, including the planning process, from beginning until completion.
As mentioned previously, at Wandsworth Sash Windows, we can manage the whole planning process for you, and we charge £495 plus VAT. This includes:
£50 for required purchasable items such as digital maps to show where the property is.
The remaining cost is for our time to produce and complete the following statements and tasks required:
- Planning team to undertake a site visit to inspect the proposed works in detail, take pictures of the existing property and measure as required to produce drawings.
- Produce technical drawings of the proposed works including scale section and elevation drawings, as well as detailed drawings.
- Produce a report on the condition of the existing property to try to highlight the reasons that the works are necessary with images highlighting specific areas.
- Drawing elevations of the whole property.
- Provide location & block plans.
- Consulting with the council to answer any queries they may have about the application.
Our experience and knowledge with conservation areas means we very rarely need to make a subsequent application. However, if it is necessary for us to tweak the application and resubmit, we will not charge for any subsequent application that is made.
To prepare an application for a property within a conservation area, it usually takes us between two and three weeks to gather all the information, prepare, and submit it. This is where our control ends, which makes giving a precise approval time to customers very tricky.
Once the application has been submitted, the council must provide a decision within eight weeks. However, the eight-week period only starts once the application has been validated (‘validated’ simply means the council has checked to make sure everything they need has been included in the application before it is passed up the ranks for approval consideration). If the council has a backlog of requests, it is common for them to delay validating an application to buy themselves time. It is a clever tactic that ensures that statistically they remain on target. Remember, it is only once the application is validated that the clock starts ticking.
It is not unusual for the council planning department to contact us on the day a decision should be provided, to request additional information, despite not having heard from them for eight weeks. For example, the council may ask for more evidential photos to be submitted and if you are unable to provide them within the timeframe requested, they may ask us to agree on a 14-day extension of the decision date. Obviously, if we do not comply, they will refuse the application.
The planning process has become more complicated in recent years. For example, Planning Officers previously accepted photos of the elevations rather than architectural drawings to make the planning process more accessible to those who cannot afford an architect’s services. For example, if you wanted to replace your property’s front windows yourself, you were able to simply take photos of the front of your house and submit them.
Nowadays, you are required to submit detailed technical drawings of the windows in various scales, etc. Customers are not always aware of what is required and will try to apply themselves. When they realise they cannot provide the information needed, they come to us. By which time they will have already paid an application fee to the council on top of other costs, and will have to pay again to submit new drawings. Enlisting the help of a professional from the get-go will save time and money overall.