Do I Need Planning Permission for a House Extension?

Permitted Development or Planning Application?

This is one of the most common questions we receive — and the answer depends on several factors: the size and position of the proposed extension, the type of property, and your local planning context. The good news is that many extensions can be built under Permitted Development (PD) rights without a formal planning application.

What Are Permitted Development Rights?

Permitted Development rights are a set of nationally defined rules that allow certain types of development without needing planning permission. For house extensions, the key rules are:

• Single-storey rear extensions up to 4m from the original rear wall (detached houses) or 3m (semi-detached and terraced houses) — subject to conditions
• The extension must not exceed the height of the original roof
• Side extensions are limited to 50% of the original house width
• Materials should match the original house
• No more than 50% of the garden should be covered by the extension and outbuildings combined

These are simplified summaries — the actual rules have further conditions. An architect will check your specific proposal against the full PD criteria.

When Is Planning Permission Required?

You will need a planning application if:

• The extension exceeds PD size limits
• Your PD rights have been removed — common in new-build estates (Article 4 Directions)
• Your property is a listed building
• You are in a conservation area (some PD rights are restricted)
• You are in an Area of Outstanding Natural Beauty — significant parts of the Isle of Wight fall within the AONB
• The property is a flat or maisonette (flats have no PD rights for extensions)

Isle of Wight Planning Context

The Isle of Wight has a particularly complex planning environment. A large proportion of the island falls within the AONB and/or the National Landscape designation. Many villages and towns also have conservation area designations. This means that extensions which would be straightforward in other areas may require a planning application on the island.

Isle of Wight Council planning officers generally require extensions to respect the character of the local area — materials, scale, and roofline are all scrutinised carefully.

The Neighbour Consultation Scheme

For larger rear extensions (4–8m for detached, 3–6m for semi/terraced), a Neighbour Consultation Scheme applies under Permitted Development. This is not a full planning application, but allows neighbours to object. An architect can manage this process for you.

Do You Need an Architect for Permitted Development?

Even if planning permission isn’t needed, you still need Building Regulations approval — and you’ll need detailed drawings for contractors to price and build from. An architect handles all of this, ensuring your extension is well-designed, structurally sound, and compliantly built.

Visit our FAQ page for more common questions, or book a free consultation to discuss your specific situation. Our team works across the Isle of Wight, London, and the South Coast.