One of the most common questions we get from homeowners in Barnet and North London is: do I need planning permission for my extension?
The good news is that the majority of house extensions in Barnet can be built under Permitted Development rights — meaning no formal planning application is required. But the rules have conditions, limits and exceptions, and getting it wrong can be costly.
What is Permitted Development?
Permitted Development (PD) is a set of national planning rules that grant homeowners automatic planning permission to carry out certain types of work — including extensions — without needing to submit a full planning application to the council. However, Permitted Development rights can be removed in certain areas, and there are specific size and design limits that must be met.
Single-Storey Rear Extensions — Permitted Development Rules
A single-storey rear extension can be built without planning permission if: it does not extend beyond the rear wall by more than 4 metres (detached) or 3 metres (semi-detached or terraced); the height does not exceed 4 metres; materials match the existing house; and it does not cover more than 50% of the garden area. Extensions between 3–8 metres (detached) or 3–6 metres (semi-detached/terraced) require a Prior Approval application under the Neighbour Consultation Scheme.
Two-Storey Extensions
Two-storey rear extensions are more restricted: maximum 3 metres beyond the rear wall; must be at least 7 metres from the rear boundary; cannot be within 2 metres of any boundary; roof pitch must match the existing house. Many double-storey extensions exceed these limits and require full planning permission.
Side Extensions
Single-storey side extensions can be built under Permitted Development but must not exceed half the width of the original house. Two-storey side extensions always require planning permission.
When Will I Always Need Planning Permission?
You will always need planning permission if: your property is in a conservation area (including parts of Hampstead, Highgate, East Barnet and Totteridge); your property is listed; the extension exceeds PD size limits; Permitted Development rights have been removed by an Article 4 Direction; or you want a front extension.
What About Building Regulations?
Even if your extension doesn't require planning permission, it will require Building Regulations approval. We handle all Building Regulations submissions and inspections for our clients as part of our fully managed service.
We Handle All of This For You
Every extension project we undertake is fully managed from planning through to completion. Call us on 020 8441 3144 or use our Online Price Guide to get a budget estimate for your extension.