Planning & Conservation in Merton

1. Identify the Wimbledon designation precisely

Use Merton’s current map and list rather than treating “Wimbledon Village” or “near the Common” as a planning designation. The council publishes separate records for Wimbledon Broadway, Wimbledon Hill Road, Wimbledon North, Wimbledon Village, Wimbledon West and Wimbledon Windmill, each with its own boundary and available guidance.

Then check listing, any Article 4 direction, planning conditions and planning history for the address. Those controls decide whether national permitted development remains available and which heritage evidence belongs in the package.

2. Apply the current policy baseline

Merton adopted its new Local Plan on 20 November 2024 and states that applications validated after that date are considered against it. For basements, policy D12.11 addresses the built and natural environment, local amenity, flooding and ground instability; the council also continues to list its Basement and Subterranean Planning Guidance as adopted guidance.

For extensions and lofts, the proposal should be tested against the host building, local character and neighbour relationships. A precedent is useful only after its policy date, designation, site geometry and planning history have been compared with the subject property.

3. Choose householder, full application or evidence of lawfulness

Some extensions and roof alterations to a single house may be permitted development if every national limitation and condition is met. A larger rear extension can have a prior-approval route where the right remains, and a lawful development certificate can record a proposal that meets permitted-development rules.

Merton confirms that householder permitted development does not apply to flats, apartments and maisonettes. External work to those properties generally follows a full application, with separate freeholder approval where the lease requires it.

4. Build the submission around the live validation checklist

Merton’s Validation Checklist 2025 was updated in June 2026. It requires clearly named files and drawings with a title, drawing number, metric scale, scale bar, key dimensions and north arrow; existing and proposed versions should be directly comparable.

The checklist is a threshold, not a substitute for design evidence. Relevant elevations, roof plans, cross-sections, context, heritage information and specialist reports should explain the actual planning issues. An incomplete or inaccurate set can delay validation or undermine the decision.

Wimbledon extensions and lofts

The design should show how height, depth, roof form and materials relate to the host and nearby buildings, and how the proposal affects outlook, privacy and daylight. In conservation areas, the applicable Wimbledon map and design material should shape the explanation; designation should not be guessed from the postcode.

For loft rooms, Merton’s current checklist calls for cross-sections showing floor-to-ceiling heights, particularly in dormers and sloping-roof rooms. That same section helps expose stair and roof geometry before the scheme reaches building regulations.

Basements and subterranean additions

Merton’s adopted guidance says the level of technical information varies with the scheme’s type, complexity and proximity to adjoining structures. Depending on the site, the package may need assessment of drainage, flooding, groundwater and structural stability, together with site investigation, an outline construction method, tree information and neighbour-impact mitigation.

The guidance describes a basement within the original building footprint and no deeper than one full storey as often the more appropriate form, subject to internal quality and no unacceptable effect on trees, water or land stability. That is guidance, not a safe-harbour approval: the evidence and acceptable extent remain property-specific.

Refurbishments and flats

A wholly internal refurbishment of an unlisted house may fall outside planning, but structural work still engages building regulations and sometimes party wall procedure. In a flat, establish the lease, demise, freeholder process, fire and acoustic implications before assuming that no external planning change means no consent work.

Design, heritage and living conditions

The current Local Plan, the applicable conservation guidance and the site evidence are read together. Officers need enough information to assess the host building, streetscape or garden context and effects on neighbours; drawings should make those relationships measurable.

Basement risk and construction impact

For subterranean work, Merton’s published considerations include the water environment, ground conditions, structural stability, biodiversity, trees, adjoining structures, noise, vibration, construction traffic and local amenity. The correct specialists and evidence depend on the particular site rather than a standard report bundle.

Typical Merton residential planning set

Location and site plans, accurate existing and proposed floor plans, all affected elevations, roof plan where relevant and cross-sections through critical roof, level and neighbour relationships. Use clear file names, titles, drawing numbers, metric scales, scale bars, dimensions and revision dates in line with the current checklist.

Add the evidence triggered by the site: heritage detail in a sensitive designation; tree and landscape information; or, for a basement, the proportionate ground, drainage, structural and construction material identified with the technical team.