When you need planning permission in Horsham

Most single-storey rear extensions in Horsham 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 South East England.

Permitted Development limits used in Horsham

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

Horsham 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.