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Greater London

Planning permission in Merton

What homeowners in Merton need to know about planning permission before starting an extension, loft conversion or major renovation in Greater London.

When you need planning permission in Merton

Most single-storey rear extensions in Merton fall under Permitted Development (PD), provided they stay within size, height and material limits. Two-storey extensions, side-return extensions on terraces, and any work in a conservation area or to a listed building typically require a full planning application from your local authority in Greater London.

Permitted Development limits used in Merton

For detached homes, rear extensions can usually go up to 8 m deep (single-storey) without planning. For terraced and semi-detached, the limit is 6 m. Maximum eaves height is 3 m within 2 m of the boundary, and side extensions must be single-storey, no more than 4 m high, and no wider than half the original house. Always file a Prior Approval / Lawful Development Certificate to lock the rights in writing.

Conservation areas and listed buildings

Merton has several conservation areas where Permitted Development rights are restricted or removed entirely (Article 4 directions). Listed buildings always require Listed Building Consent in addition to planning. Check the local authority's planning portal before quoting builders.

Typical timelines & fees

A householder planning application takes 8 weeks for a decision. Fees are £258 for England householder applications (2026). Lawful Development Certificates cost £129. Budget 4–6 weeks extra for drawings and pre-application advice if needed.

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FAQs about planning permission in Merton

Do I need planning permission for a loft conversion in Merton?

Most rear dormer loft conversions in Merton are Permitted Development if the dormer is under 40 m³ (terraced) or 50 m³ (semi/detached) and doesn't sit on the front roof slope. Mansard conversions and anything in a conservation area need full planning.

How much does a planning consultant cost in Merton?

Typical fees are £600–£1,800 for a householder application including drawings. Pre-application advice from the council adds £150–£400 but often saves weeks on contentious schemes.

Can my builder submit the planning application?

Usually no — you need a designer or architect to prepare scaled drawings and the application. Some builders have an in-house designer, but the application is filed in the homeowner's name.

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