How far can you extend to the rear in London?

Four thresholds

• 3 m deep (terrace, semi) or 4 m (detached): permitted development under Class A.
• 6 m (terrace, semi) or 8 m (detached): the larger home extension scheme — prior approval with a 42-day neighbour consultation. Not available in conservation areas.
• Two-storey rear: 3 m deep and at least 7 m from the rear boundary.
• Beyond these: full planning permission.

Other Class A conditions

• Maximum height 4 m; eaves no higher than 3 m within 2 m of a boundary.
• Total ground covered by extensions and outbuildings no more than 50% of the original garden.
• Not forward of the principal elevation.
• Materials similar to the existing house.

The neighbour consultation scheme

For a 4–6 m extension you notify the council, who writes to adjoining neighbours. If nobody objects within 21 days, you can proceed after the council confirms. If a neighbour objects, the council assesses the impact on their amenity — usually daylight and outlook — and can refuse.

What Plan Check adds

Depth against each threshold, the 45-degree daylight rule for the neighbours, conservation and Article 4 status, and the approvals and refusals on your street in the last three years.