You have probably heard someone say “you don’t need planning permission for that.” Maybe it was a neighbour. Maybe a builder. Maybe your uncle who renovated his place back in 2014.

And they might be right. But they also might be completely wrong.

Thats the problem with permitted development. Everyone thinks they understand it. Very few people actually do.

At Extension Architecture, we get calls every week from London homeowners who started work thinking they were covered. Some were. Some weren’t. The ones who weren’t had a much worse time.

So lets go through what these rights really mean, where the traps are, and how to make sure you don’t get caught out.

What Permitted Development Actually Covers

Permitted development is a set of building rights given to homeowners by the government. They let you do certain types of work without submitting a full planning application.

Small rear extensions. Some loft conversions. Porches. Garden outbuildings. These can often be done under permitted development.

Sounds straightforward. But it isn’t.

There are height limits. Depth limits. Rules about how close you build to boundaries. Rules about materials matching the existing house.

And if your property is in a conservation area or covered by an Article 4 direction? Some of those rights disappear entirely.

Even previous extensions on your property count against your allowance. If the last owner built a small addition, that reduces what you can do now.

Why It’s Not the Same as No Rules

This trips up a lot of people.

Permitted development doesn’t mean you can build whatever you want. It means that specific types of work are pre-approved, as long as you meet all conditions.

Miss one condition and the whole thing falls outside permitted development. Then you are building without permission. That can lead to enforcement action, demolition orders, or problems when you try to sell.

Speaking of selling. Even if your project was genuinely permitted development, a buyers solicitor will usually ask for proof. Thats why we always recommend getting a lawful development certificate from the council. It costs a bit. But it protects you later.

Where Homeowners Get It Wrong

We see the same mistakes again and again.

Building too close to a boundary without checking the setback rules. Going over the maximum height. That’s 4 meters for a detached house and 3 meters for everything else on a single-story rear extension.

Using measurements from a previous extension instead of the original house. The rules are based on the original footprint, not what’s there now.

Forgetting about the prior approval process. For larger rear extensions, you still need to notify the council and give neighbours a chance to respond. Its not full planning. But its not nothing either.

And materials. Under permitted development, what you build should look similar to the existing house. You cant attach a full glass and steel box to a Victorian terrace and assume its fine.

Conservation Areas and Article 4 Directions

If your home is in a conservation area, the rules get tighter.

Front extensions, side extensions, cladding, and sometimes even window changes may need full planning permission. Work that would be permitted development on a normal street could require an application here.

Article 4 directions go even further. These are specific council orders that strip away certain permitted development rights in a defined area. You could need permission to change your front door or replace a fence.

The worst part? Many homeowners don’t know their property is affected until they check. And some don’t check until its too late.

Always verify with the council before you commit to anything. A five-minute phone call can save you thousands.

The Neighbor Factor

For larger single storey rear extensions, theres a process called prior notification. You apply to the council. They write to your neighbours. Your neighbours get 21 days to respond.

If no one objects, you get approval and can proceed.

If someone does object, the council makes a decision based on the impact. They look at things like loss of light and the effect on the neighbours enjoyment of their property.

Its worth knowing that this process only applies to certain sizes. For detached houses, extensions between 4 and 8 metres. For other houses, between 3 and 6 metres. Anything within the smaller limits doesn’t need this step.

But even within those smaller limits, you still need to meet all the other permitted development rules. There is no shortcut around that.

Why a Quick Consultation Saves You More Than It Costs

We get it. Hiring an architect or planner feels like an unnecessary expense when you think the work is permitted development anyway.

But heres what we have seen happen. Homeowners spend money on builders. Work starts. Then the council steps in. Work stops. Drawings need to be submitted retrospectively. Sometimes work needs to come down.

That costs far more than a one hour consultation would have.

At Extension Architecture, we check your property against the current rules. We look at previous extensions, local designations, conservation areas, Article 4 directions, and any other restrictions that apply. Then we tell you exactly where you stand.

London is a patchwork of different boroughs with different rules. What your neighbour did in Wandsworth might not be allowed on your street in Hammersmith. Permitted development is a useful tool, but only when you know exactly how to use it. Get the right advice first, and the rest becomes a lot simpler.