Permitted development confuses more homeowners than any other part of the planning system. Plenty of people who assume they are covered are not, and plenty who brace themselves for a planning battle never needed one.
Either way, the mistake costs money. An architect in london ends up correcting the same myths on project after project, so here they are against what the rules actually say in 2026.
Myth 1: “I’m in a conservation area, so nothing is permitted development”
Not true, and it is the one we hear most.
A conservation area does not cancel permitted development. The legislation calls it “article 2(3) land”, and what it really does is trim the rules rather than scrap them.
Usually what goes is the visible stuff: side extensions, cladding, dormers facing the road. A single storey rear extension within the normal limits often still stands, depending on the house. So before you assume the whole idea is dead, it is worth finding out which specific rights your address actually loses, because the answer is rarely all of them.
Myth 2: “Permitted development applies everywhere, so I can just crack on”
The reverse mistake, and it is the more dangerous one.
Yes, permitted development is national. But it is stacked with exceptions, and if one of them applies to your house and you build anyway, you can end up with an enforcement notice and a half finished extension you have to take back down.
Permitted development is never automatic. Confirm your property qualifies first, because several common situations quietly take it away.
Myth 3: “A flat has the same rights as a house”
This one trips up a lot of people in London, where so much of the stock is flats.
Householder permitted development rights are for houses. Flats and maisonettes are left out of the definition of a dwellinghouse in England, so those rights simply do not reach them.
For a flat, that means even modest external work will usually need a planning application rather than slipping through under permitted development. There is no householder shortcut to fall back on, so plan for the application route from the start.
Myth 4: “My neighbour did it, so I can too”
Understandable, and often wrong.
Say the house two doors down added a rear dormer last year. You assume yours is fine. But a council can use an Article 4 direction to strip permitted development rights from specific streets or even individual properties, and your neighbour’s work might predate it, or sit just outside the line it draws.
Their finished extension tells you about their address. It does not promise anything about yours.
Myth 5: “A 6 metre rear extension is automatic”
A lot of homeowners think the bigger depths, up to 6 metres on a semi or terrace and up to 8 on a detached house, are theirs by right. They are not.
Those depths only come through the prior approval process, the Larger Home Extension Scheme. You notify the council, your neighbours get a consultation window, and if one objects on fair grounds the council can refuse. The usual conditions still apply on top: the height caps, the rule that extensions and outbuildings cannot cover more than half the land around the original house, and the fact that an already extended house may have used up its allowance.
And none of it works on article 2(3) land. In a conservation area, National Park or area of outstanding natural beauty, the larger scheme is off the table entirely.
So it is permitted development with a process and strings attached, not a free pass. Where your rights are intact, the depths you can build with no application at all are 3 metres on a semi or terrace, 4 metres detached.
Myth 6: “If it’s permitted development, there’s no paperwork”
Skip the paperwork here and it comes back to bite you when you sell.
Even genuine permitted development is worth confirming with a Lawful Development Certificate, which is the council’s written proof the work was lawful. On top of that, almost every extension needs Building Regulations sign off, and that is a separate system from planning altogether.
Permitted development gets you out of the planning application. It does not get you out of the proof or the building control inspection. Working out exactly what your job needs under the permitted development rules is what saves you an awkward conversation with a buyer’s solicitor later.
Myth 7: “Permitted development is quicker, so it’s always better”
Quicker, yes. Always better, no.
Permitted development skips the full application, which saves weeks. But it also boxes you into fixed limits, and a design forced to fit those limits can end up worse than one that applies for full permission and gets the layout the house really wants. We have seen people shave a metre off a much better scheme just to stay inside the rules, and regret it.
It is a route, not a reward. On some plots it is the obvious choice. On others, a full application buys a far better extension, and the extra time pays for itself.
The Thread Running Through All Seven
Every myth here comes from the same place: treating permitted development as a flat yes or no, when it actually bends with your property type, your street, and what has already been built on the plot.
That is why the first useful thing anyone can do is check their own address before falling in love with a design. Extension Architecture treats that screening as step one, which is how a scheme like the South Croydon project, refused under an earlier design and then reworked into an approval, got back on track. The constraints were pinned down before the drawings were. Permitted development looks after the homeowner who checks, and catches out the one who guesses.
