Do you need planning permission for an extension?
The three routes a UK home project can take, how to tell which is yours, and why a certificate is worth having afterwards.
Short answer: often not. Many extensions fall under permitted development. Here's how to tell which camp yours is in before you spend anything.
Planning is where most home projects stall, and usually before a single wall is drawn. Almost every householder project follows one of three routes, and identifying yours early is what keeps the job on time and on budget.
Most home projects follow one of three routes. Knowing which one applies to your property, before you design anything, is what keeps a project on time and on budget.
The three routes
Permitted Development means the work is already allowed within nationally set limits, so no application is needed. Prior Approval covers larger single-storey rear extensions, where you notify the council and they consult your neighbours. Full Planning is a complete application, assessed on design, scale and impact.
Almost every householder project sits in one of the three. The expensive mistake is assuming the first when you are actually in the third.
When permitted development usually applies
As a general guide, and always subject to your specific property:
- Single-storey rear extensions within the depth and height limits
- Loft conversions that keep the existing roof shape and stay within volume limits
- Garden rooms and outbuildings for purposes incidental to the house
- Most internal alterations, though Building Regulations still apply
When you will usually need full planning
Two-storey extensions, side extensions beyond half the width of the house, anything forward of the principal elevation, and almost any external work to a flat, a maisonette or a listed building.
Location matters as much as the work itself. In a conservation area or on designated land, projects that would be permitted elsewhere need an application.
The questions that decide your answer
Five things determine the route, and all five are specific to your address.
- Is the property a house, or a flat or maisonette?
- Detached, semi-detached or terraced?
- Has it been extended before, and by how much?
- Is it listed, or in a conservation area or an Article 4 area?
- Does the original planning permission carry conditions removing rights?
Why a certificate is worth having
Permitted development produces no paperwork. A lawful development certificate is written confirmation that your project was allowed, and it is what a buyer's solicitor looks for years later. It is not compulsory, and it is far cheaper than resolving the question during a sale.
Getting a definite answer
General rules only take you so far, because the answer depends on your property and its history. A written route check settles it before you spend anything on design, and it is the first thing we do on every project.
Where we come in
We confirm which route applies to your property in writing, free, prepare the drawings, and handle the application with the council. See planning applications, or get your drawings quoted with no obligation. If any application we submit is refused, you get a 100% refund within 5 days.
Routes, timescales, and what actually gets applications approved.