Merton Council

Adopted Documents We Assess Against

Development plan: Merton Local Plan (adopted 20 November 2024)

Documents are re-checked against the council's own website weekly. A detected change flags "Policy Update Available" for human review — live assessment standards are never replaced automatically.

Merton Council standards at a glance

2 numeric standards taken from Merton Council's own adopted documents, each shown with the paragraph it comes from. Figures differ between councils — these are this one's.

Design character

up to 50%

A basement under your existing house can spread out beyond the original walls by up to half the footprint of the original house. A basement entirely under the existing house is nil against this test. It also has to stay a single storey. Merton Local Plan Policy D12.11(6)

Amenity neighbouring

at least 50m²

Each new house in Merton needs at least 50 square metres of private garden, and it has to be one usable regular-shaped space rather than several scraps added together. Less than that is possible on a tight site but you have to justify it in the application. Merton Local Plan Policy D12.3(q)

Standards are what the council normally expects, not a guarantee. A scheme outside them can still be approved on its merits, and one inside them can still be refused for another reason.

Authored Policy Library

7 local policy checks, each citation-locked to the adopted document. National policy (NPPF, national space and daylight standards) applies alongside these.

Merton Local Plan

• Merton Local Plan Policy D12.4(2)(a)-(b) — Two storey rear Merton expects an extension to be clearly subordinate in scale and bulk to the original house and to fit the character of the area - there is no fixed depth or height limit, it is judged on design merit.
• Merton Local Plan Policy D12.4(2)(c)-(d) — Design materials Materials should match the existing house, and the extension should not create an unbroken run of rear additions along a terrace that damages the street's character.
• Merton Local Plan Policy D12.4(2)(e), (h) — Amenity neighbouring Merton asks you to demonstrate that your extension does not significantly overshadow or overlook a neighbour. There is no Merton figure to measure against - so if the works could noticeably affect a neighbour's light, outlook or privacy, expect to submit the evidence that shows why it is acceptable.
• Merton Local Plan Policy D12.4(2)(g) — Roof alterations A dormer in Merton needs to sit comfortably within the existing roof form and match the character of the area rather than dominate it - there is no fixed size limit in the Local Plan.
• Merton Local Plan Policy D12.11 — Design character A Merton basement needs four supporting documents before anything else - an impact assessment, a drainage strategy, a construction method statement and a traffic plan. Nothing may go under the public highway, and the council looks at the effect on neighbours during the build as well as afterwards.
• Merton Local Plan Policy D12.11(6) — Design character A basement under your existing house can spread out beyond the original walls by up to half the footprint of the original house. A basement entirely under the existing house is nil against this test. It also has to stay a single storey.
• Merton Local Plan Policy D12.3(q) — Amenity neighbouring Each new house in Merton needs at least 50 square metres of private garden, and it has to be one usable regular-shaped space rather than several scraps added together. Less than that is possible on a tight site but you have to justify it in the application.