One of the first things homeowners ask me is whether they can do the work under permitted development rather than planning permission. It’s a good instinct. Permitted development avoids a planning application, and for a straightforward extension it can be the simplest route.
The trouble starts when the design is drawn to fit permitted development before anyone has asked whether that’s the right route for the house, or whether the house still has those rights at all. This post is about that choice. If you want the basic limits first, do I need planning permission for an extension? sets them out.
What is the difference between permitted development and planning permission?
Permitted development rights are a planning permission granted in advance, nationally, for certain kinds of work to houses, with fixed limits. If the work stays inside every limit, you don’t need to apply to the council. If it goes outside any of them, even slightly, the whole thing needs planning permission, not just the part that is over.
Planning permission works the other way. Instead of a fixed checklist, the council judges your design on its merits: its effect on the neighbours, the street and the character of the area, against its own local plan and design guidance.
So one is rigid and quick. The other is flexible and slower. The council can’t refuse a permitted development scheme because it dislikes the look of it, but it can’t approve one that is 10 centimetres too deep either.
The limits are specific. A single-storey rear extension can usually go 3 metres beyond the original rear wall of an attached house, or 4 metres on a detached one, up to 4 metres high. A loft conversion can add 40 cubic metres to a terraced house or 50 to a semi-detached or detached one, with nothing on the roof slope facing the road. Materials have to look similar to the house.
“Original” means the house as first built, or as it stood on 1 July 1948 if older, so earlier extensions count against the limits.
A 1960s bungalow in Woking. James led this project while at Lees Munday Architects. Photograph: Will Scott.
What about prior approval for a larger extension?
There is a halfway house. Under the larger home extension scheme, a single-storey rear extension can go up to 6 metres on an attached house or 8 on a detached one. You notify the council first, it writes to the neighbours, and it has 42 days to consider the effect on them, mainly their light and outlook. It isn’t a full application, but it isn’t automatic either, and you can’t start until you have the council’s answer or the 42 days have run out.
Does permitted development mean I can start straight away?
No. Building regulations still apply. Party wall notices may still be needed. And a lawful development certificate, the council’s formal confirmation that the work is permitted, is sensible before you build, because a buyer’s solicitor will usually ask for one later. If you need to remortgage or sell, you need a document, not an assumption.
Can permitted development rights be removed?
Yes, and this is where Surrey catches people out.
The rights are reduced in conservation areas and in the Surrey Hills National Landscape: no side extensions, no extensions of more than one storey at the back, no roof extensions, no cladding, and no prior approval route for larger rear extensions. Flats and maisonettes have no householder permitted development rights at all. Listed buildings need listed building consent for most works, permitted development or not. Heritage and conservation explains how I approach houses in those areas.
Some homes have had the rights removed. Many newer estates were given planning permission with a condition taking permitted development away, so the council keeps control over extensions. Some streets are covered by an Article 4 direction, which removes particular rights across an area. Neither shows on the house itself. You find them in the planning history and the council’s records.
Do I have permitted development rights in the Green Belt?
Usually, yes. The Green Belt does not, by itself, remove permitted development rights. Much of the land around Woking and Guildford is Green Belt, and people often assume they have no rights at all. Often they do. What the Green Belt does is make a planning application for anything larger harder, because councils look at how much bigger the house has become compared with the original building. That can make permitted development the more reliable route on a Green Belt house that has already been extended.
When is planning permission the better route anyway?
Permitted development fixes the size and shape of what you can build. Sometimes those limits suit the house perfectly. Sometimes they push the design into a shape that doesn’t work: an extension 3 metres deep when the kitchen really needs 4, a dormer squeezed to stay inside the volume allowance, a side extension that can’t happen at all in a conservation area. In those cases a planning application for the design the house needs is often the better choice, even though it takes longer.
An application also gives you room to negotiate. The officer can ask for changes and you can make them. And the permitted development rights you already have can count in your favour. If you could build something similar without permission, that “fallback” is a fair point to make in the application.
Occasionally a project is split, with one part built under permitted development and another under a planning permission. It can work, but it needs care, because each part has to stand on its own. It’s worth advice before relying on it.
A planning decision usually takes 8 to 12 weeks after the council validates the application. Nobody can promise the outcome. An application is stronger when it is built on the council’s own policies and on what has been approved nearby.
98% of the sites we have taken through planning since 2020 gained permission in the end: 79 of 81. Planning figures cover 108 decisions on 81 sites, March 2020 to October 2026, from council notices and our own records. Three appeals were allowed.
That’s a record, not a promise for your site. Some of those permissions came at the second attempt or on appeal, which is exactly why the route is worth choosing carefully at the start. More on how I approach this is on the planning advice and feasibility studies page.
What should I check before choosing a route?
Before any design work, find out four things. Whether the house still has its permitted development rights, from the planning history, any conditions and any Article 4 direction. Whether it’s in a conservation area, the Surrey Hills or the Green Belt. What has already been added since the house was first built. And what you actually need the new space to do.
Then choose the route that fits the design, not the design that fits the route. Planning permission myths deals with the assumptions that most often cause delay, and if your project is in the roof, the loft conversion page covers how the same choice plays out there.
Common questions
What happens if I build under permitted development and it turns out not to comply? The council can ask for a planning application after the event, require changes to the work, or in the worst case take enforcement action. A lawful development certificate before you build avoids that.
If my neighbour did it, can I? Not necessarily. Their house may have different rights, a different planning history, or an earlier extension of yours may already count against the limits. Each house is checked on its own.
Can the council refuse permitted development because of overlooking? Not for a standard permitted development extension. If it meets every limit, the council’s judgement about looks or neighbours doesn’t come into it. The prior approval route is the exception: there the effect on neighbours is exactly what the council considers.
This is a question the free 15-minute Clarity Call is well suited to.
