Planning permission in Merton isn't a simple yes or no — and if you're assuming your project is fine without checking, that's a risk worth thinking twice about. The rules that apply to your neighbour's identical extension might not apply to you, and most homeowners don't realise that until they're already committed. WhatCanIBuild exists precisely because the answer depends on your specific property, not a general rule.
The short version
- Whether you need permission depends on your property's specific constraints, not just the type of project
- Merton has conservation areas, Article 4 directions, and Green Belt land that can all affect your permitted development rights
- What's been approved nearby — and why — tells you more than the general rules ever will
Permitted development sounds simple. It isn't.
Most homeowners start here: "I've heard you don't need planning permission for extensions under a certain size." That's true, in some cases. But permitted development rights — the rules that allow certain works without a full application — come with conditions, exceptions, and limitations that vary dramatically depending on where your property sits and what's already been built on it.
Has your property had any previous extensions? Are there any restrictive conditions on your original planning consent? Is your home a flat, a maisonette, or a converted house? All of these things change the picture. And that's before you even factor in what Merton Council has specifically restricted in your area.
Merton has layers most boroughs don't
Merton isn't a straightforward borough. Wimbledon Village and Merton Park both sit within conservation areas, and Article 4 directions in several of these locations actively remove permitted development rights that would otherwise apply. That means works you could do freely elsewhere in London might need a full planning application here.
The south of the borough also includes Green Belt land — another layer of restriction that changes what's possible and what isn't. And scattered across the borough are listed buildings, where the rules are different again.
Here's what trips people up: knowing you're near a conservation area isn't the same as knowing whether your property is in one. And being in a conservation area isn't the same as knowing what that actually means for your specific project. The best way to understand how all of these constraints interact for your address is to use WhatCanIBuild, which shows you not just what applies, but what it means in practice.
Don't assume based on what your neighbour did
A nearby approval doesn't mean your project will be treated the same way. Different plot sizes, positions, and planning histories can produce completely different outcomes on the same street.
The question isn't just "can I build it" — it's "will it be approved"
Even if you know you need planning permission, that's only the start. Merton's typical decision time is around 8 weeks, and a householder application currently costs £258. But the real question most people don't think to ask is: what are the chances of approval for this type of project, on this street, with this property's history?
That's where general guidance runs out. What's been approved and refused nearby, how similar projects on your street have fared, and what your specific combination of constraints actually means for your odds — that's the hard stuff. And it's exactly what WhatCanIBuild surfaces when you enter your address.
If you're in SW19, SW20, SM4, CR4, or KT3, your property could sit in any number of overlapping planning zones. The best way to know where you stand is to check.
These rules vary by property
Conservation areas, Article 4 directions, and other constraints can change everything. Check what actually applies to your address.
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