The basics
Permitted development, in one paragraph
Permitted development rights are a national grant of planning permission for certain kinds of work, subject to limits on size, height, position and materials. If your project stays inside those limits, you don't need to apply for permission — the permission already exists.
Many single-storey rear extensions, many rear dormer loft conversions, most outbuildings and a lot of routine external work fall within them. That's genuinely useful, and it's why so much domestic work proceeds without an application.
The limits are specific and they are not intuitive. Depth, height at the eaves, height at the ridge, proximity to a boundary, proportion of garden covered and the materials used all have thresholds, and exceeding any one of them takes the whole scheme outside permitted development.
Watch for
The four situations where none of that applies
You live in a flat or maisonette
Permitted development rights for extensions and lofts apply to houses, not flats. If your property is a flat, assume an application is required for essentially any alteration.
You're in a conservation area
Designation restricts what can be done without consent, particularly to anything visible from the street, to the roof, and to windows and doors. Side extensions and some cladding materials lose permitted development status outright.
There's an Article 4 Direction
A council can formally withdraw specified permitted development rights across an area. This is common in London and it's the one people most often don't know about, because nothing about the house tells you. It has to be checked against the address.
The building is listed
Listed building consent is required for anything affecting the building's special character, internally as well as externally, and it's separate from and additional to planning permission. Unauthorised work to a listed building is a criminal offence, not a breach to regularise later.
Recommended
Get the certificate even when you don't need permission
Where your work does fall within permitted development, you can apply for a Lawful Development Certificate. It isn't planning permission — it's the council confirming in writing that permission isn't required.
It costs a fraction of a full application and it takes weeks rather than months. What it buys you is certainty now, and evidence later.
"Later" is the point. When you sell, the buyer's solicitor will ask what consents exist for the extension. "We were told it didn't need any" is a considerably weaker answer than a certificate, and the difference regularly shows up as a price reduction or a retention at exchange.
Different thing
Planning permission is not Building Regulations
These are two separate systems and people conflate them constantly. Planning is about whether you may build it — appearance, scale, impact on neighbours and the area. Building Regulations are about whether it's built safely and properly — structure, fire, insulation, drainage, ventilation, electrical and gas safety.
You can need one without the other. A loft conversion under permitted development needs no planning permission but absolutely needs Building Regulations approval. Repainting a listed building's front door may need listed building consent but no Building Regulations at all.
Building Regulations approval is the one that produces the completion certificate a buyer's surveyor will ask for. Don't skip it because planning wasn't needed.
Common questions
Check with your local planning authority — most publish a map or a searchable list, and the property search on their planning portal will usually flag it against the address. It's a two-minute check and it changes what's possible, so do it before commissioning a design.
The statutory determination period for a householder application is eight weeks from validation, though validation itself can take a couple of weeks and extensions of time are common. Budget three to four months realistically, and longer if the scheme is contentious or the property is listed.
The council can require you to apply retrospectively, and can refuse and issue an enforcement notice requiring removal. Even where enforcement doesn't follow, the absence of consent surfaces at sale and reduces the price. For a listed building it's more serious again — unauthorised work is a criminal offence.
Not by itself. Objections are considered against planning policy, and only material planning considerations carry weight — overlooking, loss of light, scale and appearance do; loss of a view, or the disruption of the building work, generally don't.
