Do I Need Planning Permission for a Rear Extension?

There's also the larger home extension scheme (sometimes called the "neighbour consultation scheme"), which allows single storey rear extensions up to 8 metres for detached houses and 6 metres for others — subject to a prior approval process where neighbours can object.

These are the headline rules. But there are important exceptions.

When You Will Need Permission

Even if your extension falls within the size limits above, you'll still need to apply for planning permission if:

You're in a conservation area. Permitted development rights are restricted. Many extensions that would be allowed elsewhere need a full application in conservation areas.

Your home is a listed building. You'll need listed building consent in addition to any planning permission.

Your home is a flat or maisonette. Permitted development rights for extensions don't apply to flats.

Your permitted development rights have been removed. Some properties have had PD rights stripped by condition (often called an Article 4 direction). This is common in conservation areas and some newer developments.

You're going bigger than the limits. Deeper, taller, or wider than what's permitted means you need to apply.

If You Do Need Permission — What Are the Odds?

This is where most guides stop. They tell you the rules and wish you luck. But if you're one of the thousands of homeowners who does need to apply, the question that matters most is: how likely am I to get approved?

We can answer that with data.

Rear extensions are among the most commonly approved project types in UK planning. They're familiar to planning officers, there's usually strong local precedent, and the impact on the street scene is minimal (because they're at the back).

But — and this is the important bit — that national average hides significant variation.

See what gets approved in your council →

Your Council Changes the Picture

Some councils approve rear extensions at rates well above 90%. Others are notably tougher — particularly in London and parts of the South East where plots are smaller and neighbour impact is a bigger concern.

Within councils, ward-level rates can vary by 15–20 percentage points. A rear extension in one part of your borough might be a near-certainty. In another part — especially if you're near a conservation area — it could be a genuine coin toss.

Knowing where your specific area sits on that spectrum is the single most useful piece of information you can have before spending money on an architect.

What Gets Rear Extensions Refused

When rear extensions are refused, it's usually for one of a few reasons: the extension is too deep and overbears on a neighbour's garden, it causes loss of light to an adjacent property, the design doesn't match the existing house, or it results in overdevelopment of the plot.

Two-storey rear extensions face higher scrutiny than single storey ones. They're taller, more visible, and have more impact on neighbours. If you're considering going to two storeys, checking what's been approved nearby is particularly important.

Before You Start

Whether you need permission or not, a rear extension is a significant investment. Doing your homework before you commit to drawings can save you thousands — and months of waiting.

If you're within permitted development limits and none of the exceptions apply, you're probably free to proceed (though always check with your council or get a lawful development certificate to be safe).

If you do need permission, the odds are broadly in your favour — but they depend heavily on where you are and what you're proposing. Don't assume your area is average. Check it.