Under standard permitted development, you can extend 3 metres from the rear wall on a semi-detached or terraced house, or 4 metres on a detached house for single-storey extensions. Under the Larger Home Extension scheme (which requires neighbour notification), these limits increase to 6 metres and 8 metres respectively. These measurements are taken from the original rear wall, not from any previous extensions.

Single-storey rear extensions can be up to 4 metres high under permitted development. However, if the extension is within 2 metres of a boundary, the eaves height is limited to 3 metres. Flat-roofed extensions are typically kept to 3 metres to reduce impact on neighbours. Your extension must also not exceed the height of the highest part of the existing roof.

Side extensions under permitted development must be single storey and cannot exceed half the width of the original house. The maximum height is 4 metres, and eaves must not exceed 3 metres if within 2 metres of a boundary. Side extensions cannot extend beyond the front wall of the original house, and materials should match the existing property.

Two-storey extensions have stricter limits than single-storey. They cannot extend more than 3 metres from the rear wall, must be at least 7 metres from the rear boundary, and cannot be within 2 metres of a side boundary. The roof pitch must match the existing house, and no balconies or raised platforms are permitted. Many two-storey extensions require full planning permission.

Yes. Detached houses have the most generous limits because extensions don't directly affect adjoining properties. Semi-detached and terraced houses have stricter limits, particularly at shared boundaries. Flats and maisonettes have very limited permitted development rights and usually require planning permission for any external changes. Your property type is one of the most important factors in determining what you can build.

The Larger Home Extension scheme allows larger single-storey rear extensions under permitted development, but requires a neighbour consultation process. You can extend up to 6 metres on attached houses or 8 metres on detached houses. You must notify your council, who will inform adjoining neighbours. If no objections are raised within 21 days, you can proceed. If neighbours object, the council makes a decision.

The original house means the house as it was built, or as it stood on 1 July 1948 if built before then. Any extensions added after that date don't count as original. Measure from the rear wall of the original house, not from conservatories, previous extensions, or outbuildings added later. If you're unsure what's original, check your property's planning history or the deeds.

Your neighbour's extension doesn't change what you're allowed to build under permitted development. The size limits apply to your property based on its original footprint, not what others have built. However, if your neighbour's extension required planning permission and was approved, it may indicate the council is receptive to larger extensions in your area, which could help if you apply.

Yes. In conservation areas, permitted development rights are reduced. You cannot add extensions to the side of your house, cladding is restricted, and rear extensions are more limited. Any extension that would be visible from a public highway may require permission. Some conservation areas have additional restrictions through Article 4 directions. Always check your local constraints before assuming PD applies.

Approved sizes vary by council and context, but most householder applications succeed when the extension remains subordinate to the original house, doesn't breach the 45-degree line from neighbour windows, and respects local character. In practice, rear depths of 3 to 4 metres are commonly approved on terraced streets, while detached properties often achieve 4 to 6 metres. Local precedent matters more than national averages.