Merton planning: a Local Plan adopted in November 2024, 28 conservation areas and 92.2% of householder cases approved

Why does Merton approve so many cases and still refuse nearly a third of its big extensions?

Merton refused 60 of its 769 householder applications. That puts it 8th of the 32 boroughs with a published figure, 92.2% against England's 90.3%. Speed is the weaker side. Of 499 standard decisions, 439 came within eight weeks, 88.0%, which is 29th of 32. A further 270 decisions were made under a planning performance agreement or an agreed extension of time, 263 of them in time, and the eight-week measure leaves those out.

Large home extensions on the prior approval route are decided differently. Merton decided 254 and refused 80, 31.5%. Of the 24 boroughs with a published rate that is the 8th highest. The statistics give no reasons, so read the figure as a reminder that a 6m rear extension still has to pass the neighbour test, and not as a verdict on any one scheme.

Appeals sit close to the national picture. The Planning Inspectorate allowed 36 of 101 householder appeals against Merton over five years, 35.6%, 24th of 32 and 1.2 points above the national rate, but 4.3 points below London's. A refusal here is reversed a little more often than across England and less often than across London.

How many conservation areas does Merton have?

The council's list page states no total. It has 29 headings under A to D, J to L, M to V and W. One of them, The Canons, carries a conservation management plan that the council adopted as a supplementary planning document on 18 September 2017. Excluding it leaves 28 named areas, and the national planning data register also records 28 for Merton. We have counted the headings ourselves and we have not asked the council to confirm the figure, so treat the council's own list and map as the document that decides.

The 28 are Bathgate Road, Bertram Cottages, Copse Hill, Cricket Green (Mitcham), Drax Avenue, Dennis Park Crescent, Dunmore Road, Durham Road, John Innes: Merton Park, John Innes: Wilton Crescent, Kenilworth Avenue, Lambton Road, Leopold Road, Merton Hall Road, Pelham Road, South Park Gardens, Upper Morden, Vineyard Hill Road, Wandle Valley, Westcoombe Avenue, Wimbledon Broadway, Wimbledon Chase, Wimbledon Hill Road, Wimbledon North, Wimbledon Village, Wimbledon West, Wimbledon Windmill and Wool Road.

Status changes the route. A dormer is an enlargement of the roof, and Class B of Part 1 of the General Permitted Development Order does not apply on article 2(3) land, which includes conservation areas. The council's application page also says that permitted development for householder extensions and alterations is "does not apply to flats, apartments and maisonettes" and "is also restricted for some types of development in Conservation Areas as well as for listed buildings and new build homes". Our guide to conservation areas and Article 4 directions in London sets out the national rules.

What does conservation area status mean in Wimbledon Village, Wimbledon North and Wimbledon West?

Wimbledon's conservation areas come with long documents. The council's list gives Wimbledon Village a design guide whose file labels run to page 40, Wimbledon North a character assessment split into six sub-areas, and Wimbledon West a character assessment that runs through 33 sub-areas from the Cannizaro arm to Copse Hill. Wimbledon Hill Road, Wimbledon Broadway, Wimbledon Chase and Wimbledon Windmill are separate areas with their own maps.

The Local Plan adds the open land. Its text says the whole of Wimbledon Park is designated as Metropolitan Open Land, open space and green corridor, and lies within the Wimbledon North conservation area. It describes Wimbledon Village as a local centre whose unique character the plan wants to maintain, and it mentions Wimbledon Common alongside it.

A heritage statement belongs with any application that could affect a conservation area, and the validation checklist asks for details at a scale of not less than 1:20 for external works in conservation areas. Merton's heritage policy also says the loss of a building that makes a positive contribution to a conservation area should be avoided.

Do basements, flooding and the River Wandle change a Merton application?

They can. The basement policy allows one storey only, no more than 50% of the original dwelling's footprint beyond its outer walls, and nothing under the public highway. Every basement application needs a basement impact assessment, a drainage strategy, an outline construction method statement and a construction traffic management plan. In conservation areas the policy says basements will be supported where they conserve or enhance the area. The council's Basement and Subterranean SPD of 2017 supplies the detail, and we have not read it in full.

Flood policy F15.8 asks that buildings be set back at least 8m from the top of the bank of a main river and 5m from an ordinary watercourse. The validation checklist asks for a flood risk assessment in Flood Zones 2 and 3, for larger sites in Flood Zone 1 and in areas of critical drainage. Dwelling conversions in Flood Zone 3b may not increase footprint, units or bedrooms, and in Flood Zone 3a self-contained basements and basement bedrooms are not permitted. Our basement conversion plans service covers the drawings these reports sit behind.

The Wandle Valley is also a conservation area in its own right, divided into six sub-areas from Copper Mill Lane to Lower Mitcham, and the council's page links a proposed Article 4(2) direction for it without a date. Trees count too: policy O15.4 expects development to retain trees and hedges of amenity value and says the council uses Tree Preservation Orders.

What about flat conversions and HMOs in Merton?

Both need care. Policy D12.10 says that converting a home of three or more bedrooms into smaller units must re-provide at least one family-sized home, and the supporting text names the gridiron terraces of areas such as Abbey, Colliers Wood, Dundonald and Graveney as places where conversions are prevalent. A flat is not a house, so the householder permitted development rights in Part 1 do not apply to it, and an extension to a flat needs a full application.

For HMOs the council's page says that converting a home to an HMO of any size anywhere in Merton needs planning permission, because of the two small-HMO directions in the table above. Licensing is a separate regime. The council's pages link HMO licensing and a consultation on proposed landlord licensing, which we have not read. An HMO supplementary planning document consulted on from 19 June 2023 is listed in the council's SPD index under the adopted heading but labelled draft, and the page does not confirm adoption. Our guide to HMO planning permission in London covers the planning side.

Can you get advice from Merton before you apply?

Yes. The council's pre-application page lists eight categories from A+ to D plus a concept meeting. Category D covers householder development and lawful development certificates, and gives verbal advice in a 15-minute virtual meeting. You book it by emailing the completed form to the pre-application address, appointments run Monday to Friday between 9am and 11am, and the page gives two timings: booked within three days, and a meeting within 10 working days. Category D+ covers minor works and ancillary annexes. The page gives the written summary as due within ten working days of the meeting in one place and within 20 working days of the request in another, with up to 10 more where specialist input is needed. The council says its targets are not guaranteed.

Two council pages disagree on the duty planner. The pre-application page says a customer service officer can take simple planning queries on 020 8545 3777 from 9am to 5pm Monday to Friday and cannot discuss site-specific applications. The application page gives the same number for Monday to Friday between 1pm and 3pm. Ring in the afternoon window if you want to be sure someone is there.

The council's application page also asks you to check your address against its Article 4 page and conservation area list first, and to search your address on its planning register for rights removed by condition.

What should you check first for Merton planning?

Check the address against the council's conservation area list, then its Article 4 page, then the validation checklist. Those three decide whether a loft, rear extension or outbuilding can use permitted development or needs an application read against policy D12.4, the 45 degree line and the neighbours' windows. If the property is in Merton Park, Wimbledon Village or the Wandle Valley, read the area's own design guide or character assessment as well. The 2024 Local Plan is the policy base for everything else.