Two-storey extension planning permission and PD rules

Some two-storey rear extensions can qualify as permitted development in England. A two-storey side extension does not qualify under the ordinary Class A side extension rules. The location and complete design matter as well as the number of storeys.

What are the main rear extension tests?

For an enlargement of more than one storey under Class A, the projection beyond the original rear wall must not exceed 3 metres, and it must not be within 7 metres of a boundary opposite that wall. Roof pitch should match the existing house as far as practicable; upper-floor side windows have glazing and opening conditions.

These rear extension rights do not apply on designated land, including conservation areas. Other height, materials, coverage and eligibility rules still apply. See the Planning Portal's full extension conditions. These selected limits are not a complete design checklist.

Can you add a storey over an existing extension?

Assess the complete enlargement rather than only the new upper floor. Start by identifying the original house and obtaining the drawings and decision for the existing extension. An existing ground-floor footprint does not establish that a new floor above it is permitted.

Mark the proposed roof, windows and distances to boundaries on a plan and elevation. Explain which spaces you need and where stairs could go. This gives the initial assessment a concrete design to examine rather than an assumption that the upper floor will simply follow the walls below.

What if the proposal needs planning permission?

Find your council and review its current residential design guidance and comparable decisions. Compare building form and neighbouring relationships, not just whether another application was approved.

For a scheme extending both sideways and backwards, read the side extension guide and rear extension guide together. The larger single-storey extension procedure should not be applied to a two-storey proposal.

How do you confirm the route?

Start with the permitted development checker and identify all the proposed work. If the scheme qualifies without a planning application, consider a lawful development certificate for formal confirmation.

Allow separately for design preparation and the planning decision period. Structural design and building regulations approval also need attention before construction, regardless of the planning route.