So, you’re planning on having an extension built?
It’s perfectly logical to make the most of the space you have. You may even be able to construct your extension without planning permission under what’s known as Permitted Development.
Permitted Development allows homeowners to build or change things on their properties (to a reasonable level). They must be for the benefit of the ‘enjoyment’ of the home, which is somewhat up to personal interpretation.
It sounds fantastic at first glance, right? And it is. However, there are several restrictions to the process, including where you live and the size of your planned extension and existing land.
Let’s learn more about that in this blog post.
Permitted Development and home extensions
Permitted Development dates back to 2015. The idea was to give homeowners more freedom with what they can construct or modify on their own premises instead of going through the challenging process of getting planning permission every time.
Planning permission has become the norm for several reasons, the primary ones being safety, the local landscape and culture, and the opinions and privacy of neighbours. It gets a bad rep, but in fairness, there’s a place for it.
Now, instead of going through the long and somewhat arduous process of obtaining planning permission, you can go straight to the next stage – provided you meet the Permitted Development criteria.
We’ll discuss which homes are eligible and which aren’t in the following section.
Home extensions are classified under Permitted Development Class A. You can move straight to the neighbour consultation scheme if you meet specific conditions.
Although the extension itself comes under Class A, any additional changes to the building have their own classification. For example, you’ll likely need to expand your roof if constructing a large side or rear extension (Class B). You might install a new chimney (Class G), satellite dish (Class H) or an outdoor porch (Class D). Each of these must be treated separately.
Some homes don’t meet Permitted Development criteria
Unfortunately, many homes aren’t eligible for Permitted Development of any kind. It depends on your local authority’s specific guidelines, but generally, the following places have many more restrictions:
- AONBs (Areas of Natural Beauty)
- National Parks
- Conservation Areas
Permitted Development also doesn’t usually apply to listed buildings. In these cases, you’ll almost always need to go through the full planning permission process to make any changes to your home.
You can’t claim Class A rights if your building was converted to residential from commercial use under a different Permitted Development class. Laws are in place to prevent the system from being played that way.
When considering a home extension, the relevant sizes (of the existing house, the extension, and the lot as a whole) also come into play. These will be discussed in more detail below.
Prior Approval Notification and Planning Permission
There are two other aspects to be aware of when it comes to building an extension – Prior Approval Notification and Planning Permission. Understanding the difference between Permitted Development, Prior Approval Notification and Planning Permission can be helpful when you’re considering making changes to your home.
Permitted Development is a bit like having a ‘green light’ for certain types of home improvements without needing to apply for Planning Permission. For instance, if you have a detached house, you can extend up to four metres to the rear under PD, meaning you can do this without seeking permission, as long as you meet specific criteria and guidelines.
Prior Approval Notification is more like an ‘amber light’. It’s a process where, for certain types of development under PD (like extending your home from four to eight metres), you need to notify your local planning authority. They will then consult your neighbours and consider any potential impacts. If there are no objections and the development meets certain criteria, you can proceed without a full planning application.
Planning Permission is the ‘red light’ scenario, where you need to stop and apply for permission. If you want to extend your home by more than eight metres (for a detached house), this falls outside PD, and you’ll need to apply for planning permission. This process involves a detailed review by your local planning authority, considering various aspects like design, impact on neighbours, and the environment.
Each of these routes has its own set of rules and requirements, so it’s always wise to check with your local planning authority or seek professional advice to make sure you’re on the right track.
Maximum size of a home extension under Permitted Development
After some research on your local council’s website or by giving the planning department a ring, you may have decided that your house is eligible for Permitted Development. So, what’s allowed under a Class A home extension?
Several rules and size restrictions apply. Here are the most important ones to know about:
- Single storey rear extension
- Must be less than four metres high
- Detached buildings: less than 4m expansion; Other buildings: less than 3m expansion
- Single storey rear extension requiring prior approval
- Must be less than four metres high
- Detached buildings: less than 8m expansion; Other buildings: less than 6m expansion
- The total floor space of your new extension must be less than 50% of the lot size, subtract the original house’s footprint.
Confused? We’ve barely started, unfortunately. You’ll find all sorts of restrictions on side extensions, rear extensions, side extensions that extend beyond rear walls, building materials, window types, etc. For example:
- Two-storey rear extension
- Must meet requirements of Class A (enlargement of the house) and Class C (alterations to the roof) for PD.
- If including a dormer window, it must also meet Class B requirements.
- Extensions and other buildings must not exceed 50% of the curtilage.
- The height of the enlarged part must not exceed the highest part of the existing roof.
- The eaves’ height of the extension must not exceed that of the existing dwellinghouse.
- Extensions must not extend beyond the principal elevation or a side elevation fronting a highway.
- Side extension
- Local planning authorities may remove PD rights through an Article 4 Direction; check with the local authority.
- Detailed rules and conditions apply, including size limits and necessary compliance.
- Loft Conversion
- Upper-floor windows in a side elevation must be obscure-glazed and non-opening unless above 1.7 metres from the floor.
- The roof pitch of the enlarged part must match that of the original dwellinghouse.
- The enlargement must not exceed the height of the highest part of the existing roof.
- Development must not extend beyond the plane of any existing roof slope fronting a highway.
- The volume increase of the roof space should not exceed 40 cubic metres for terraced houses and 50 cubic metres for others.
- Alterations including balconies, verandas, or changes to chimneys, flues, and pipes require planning permission.
- In protected areas (e.g., National Parks), roof extensions require planning permission.
- Exterior materials used must visually complement the existing dwelling.
Read through the entire document here, or get in touch with us to ask us more about what can and can’t be done under Class A Permitted Development.
If you’re in any doubt (and the rules can be extremely confusing), get yourself a Lawful Development Certificate. An LDC is a legal interpretation of the rules. They can take a while to come back sometimes, but if you’re granted this certificate, you should be fine to commence work.
You’ll need to have the drawings and plans ready for submission to get an LDC.
Neighbour Consultation Scheme
A Class A development must incorporate a neighbour consultation scheme before you start the work. This is a twenty-one-day declaration of intent to your neighbours submitted by the council.
If there are no complaints, your work may proceed. A formal hearing will decide on the best interests going forward if there are. Just because there’s some opposition doesn’t mean your extension will necessarily fail to go through. Take some comfort here if you have difficult neighbours.
Get Design Living Space’s assistance
Permitted Development does make things a lot easier, but it’s still by no means a simple process. Your extension might meet the generic size restrictions set out above, but there are still many other things to consider.
Your best option is a consultation with a planning agent or a lawyer. Get yourself that Lawful Development Certificate if you’re unsure. It’s much better to take a little extra time than have the council show up mid-build and demand you stop.
Here at Design Living Space, we combine experience and know-how with a friendly attitude. We love getting to know our clients and understanding what their extension really means to them.
We offer professional planning drawings and structural calculations, which are vital before you hire a builder or request an LDC.
Beyond that, we can also act as your planning agent with the local council (should any difficulties arise) and project manage everything for you. Whatever you need, no matter how small or large you want our involvement to be, we can help.
Interested in what we can offer? Why not get in touch for an obligation-free chat where we’ll explain who we are and get to know you. You won’t be bound by any commitment – we just want to see how we can help. We look forward to hearing from you.