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Planning guide · Merton

Permitted development in Merton

Single-storey rear extensions, lofts and side extensions you can build in Merton without full planning — and the exceptions.

Quick answer

Borough
Merton
Planning authority
Merton Council
Conservation areas
28
Statutory determination
8 weeks
Our approval rate
98% first time

Architectural design tools and technical drawings — planning drawings in Merton

How does Merton treat the deeper rear extension?

Sceptically. Merton refused 246 larger home extension notifications and granted 58, a 19.1% grant rate against 34.6% across London, though it told 431 households no prior approval was needed at all. It issued only 156 lawful development certificates over the same window.

Larger home extension routeMertonLondon
Prior approval not required4319,067
Granted581,930
Refused2463,646
Grant rate19.1%34.6%
Lawful development certificates15636,657
Decisions delegated to officers99.3%97.0%

Sources: MHCLG District Planning Application Statistics (PS1 and PS2), twelve quarters to March 2026. A zero in this return means the measure was not recorded for that borough, never that no such decisions exist. Open Government Licence v3.0.

In detail

Answers for Merton

What can I build under PD in Merton without planning?

Single-storey rear extension up to 3m deep (attached house) or 4m (detached); side extension up to half the original width; loft conversion up to 40m³ (terraced) or 50m³ (semi-detached); single-storey outbuilding within the curtilage; replacement windows and doors. All subject to material match, eaves setback (20cm), and not facing a highway.

Does Permitted Development apply to flats in Merton?

No. Permitted Development rights apply only to houses (Class C3 dwellings). Flats and maisonettes require full planning for almost every external alteration.

Are PD rights different in a conservation area?

Yes — significantly reduced. In a conservation area: side extensions and two-storey rear extensions are not PD; cladding is not PD; chimney removal needs planning; roof additions are restricted.

What is a Lawful Development Certificate?

An LDC is a formal confirmation from the council that your proposal is lawful PD — recommended before building, useful when selling. Costs around £103 for council fees + drawings.

Do I need building regulations even under PD?

Yes. Building regulations are entirely separate from planning. Permitted Development removes the planning requirement only — you still need building control sign-off for structure, insulation, fire safety, drainage, and ventilation. We deliver both planning and building regs drawings.

Related guides for Merton
Permitted development in Merton — the exterior of London house before works
The exterior of a london house before works — permitted development in Merton.
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Which postcode districts around Merton do we cover for permitted development scheme work?

Every Merton postcode district we draw in, the stock that dominates it and the authority that validates a permitted development scheme there. Merton fees below are the statutory England rates for 2026, not permitted development scheme estimates.

PostcodeAreaDominant stockWhat it means for a permitted development scheme
SW19Wimbledon / Colliers WoodVictorian villas, Edwardian terracesA permitted development scheme in Wimbledon / Colliers Wood may land with Merton Council or Wandsworth Council — SW19 crosses the boundary, and the SW19 policies map decides it street by street.
SW20Raynes ParkVictorian villas, Edwardian terracesSW20 covers Raynes Park only; Merton Council handles the permitted development scheme.
SM4Morden1930s semi-detached, post-war flatsSM4 covers Morden only; Merton Council handles the permitted development scheme.
CR4Mitcham1930s semi-detached, post-war estatesCR4 covers Mitcham only; Merton Council handles the permitted development scheme.
SW16Streatham / NorburyEdwardian terraces, post-war flatsSW16 straddles a boundary: Streatham / Norbury addresses fall to Lambeth Council or Wandsworth Council or Merton Council or Croydon Council, so confirm which authority validates the permitted development scheme before submitting SW16 drawings.
SW17Tooting / EarlsfieldEdwardian terracesSW17 straddles a boundary: Tooting / Earlsfield addresses fall to Wandsworth Council or Merton Council, so confirm which authority validates the permitted development scheme before submitting SW17 drawings.

How does a permitted development scheme differ street by street across Merton?

Roof pitch, wall build-up and plot depth change every few Merton streets, and each one changes what a permitted development scheme can achieve at that address.

How do conservation areas and Article 4 affect a permitted development scheme in Merton?

Merton conservation designations: there are 28 across Merton Council, Wimbledon Common, Wimbledon Village, John Innes among them. Designation costs a Merton owner the permitted-development route: a permitted development scheme then needs a £548 householder application over 8 weeks, in place of the £249 prior approval route that takes 6 weeks. John Innes is the Merton designation that most often changes a permitted development scheme design.

No blanket Article 4 over Merton: Merton Council has not withdrawn permitted development across Merton, so a permitted development scheme outside a Merton conservation area usually keeps it. The £274 Lawful Development Certificate is still the document a SW19 owner wants on file.

What Merton is built from: Victorian villas in Wimbledon; Edwardian terraces in Tooting and Colliers Wood; 1930s semi-detached in Morden and Raynes Park; post-war flats in Mitcham. Wimbledon is heavily conservation-controlled; outer Merton (Morden, Mitcham) is permissive. That mix decides the permitted development scheme route in Merton more than the postcode does.

Who decides a permitted development scheme on the edge of Merton?

Sources for this Merton permitted development scheme page: borough policies maps and conservation-area registers (2025–26), Royal Mail postcode district boundaries, the Town and Country Planning (Fees for Applications) (England) Regulations, the Town and Country Planning (General Permitted Development) (England) Order 2015 as amended, and the Party Wall etc. Act 1996.

An architectural technologist checking a printed set of house drawings, marking a proposed elevation in red — permitted development in Merton
Every set is checked line by line against the validation checklist before it leaves the office.

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