# Do I Need Planning Permission for an Extension?

> When your extension needs planning permission, when permitted development covers it, and what building regulations approval means — in plain English.

Source: https://renomate.co.uk/blog/extension-planning-permission

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# Do I Need Planning Permission for an Extension?

20 March 2026 · 6 min read

When your extension needs planning permission, when permitted development covers it, and what building regulations approval means — in plain English.

## The short answer

**Many single-storey extensions fall under “permitted development” and don’t need full planning permission — but larger extensions, anything at the front of the house, and most work on flats or listed buildings usually do.** Even permitted-development work must meet size limits and still needs building regulations approval.

## Permitted development limits

Broadly: a single-storey rear extension can extend up to 3m (attached house) or 4m (detached) under standard rules, or further under the Larger Home Extension scheme with a neighbour consultation. Height, materials and how much garden you cover are all capped.

## When you almost always need permission

Double-storey extensions close to a boundary, extensions to the front (the “principal elevation”), anything in a conservation area or on a listed building, and most extensions to flats and maisonettes typically need a full planning application.

## Planning vs building regulations

They’re different things. Planning permission governs what you can build and how it looks; building regulations govern that it’s structurally sound, insulated, safe and properly drained. Almost every extension needs building-regs sign-off even when planning isn’t required.

## Not sure? Get local advice

Rules vary by council and property. A good local builder or architect will confirm what applies before you start — [tell us about your project](https://renomate.co.uk/enquire) and we’ll match you with [experienced local specialists](https://renomate.co.uk/renovations/home-extensions).

## Frequently asked questions

### How much does planning permission cost?

A householder planning application in England has a fixed fee (around £250+), plus any drawings and professional fees. Building-regs fees are separate.

### How long does planning permission take?

A householder application is usually decided in around **8 weeks**. Permitted-development “prior approval” routes can be quicker.

### What if I build without permission?

The council can require you to alter or remove unauthorised work, and it can cause problems when you sell. Always confirm the position first — retrospective applications aren’t guaranteed to succeed.

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