SM4 · Morden
SM4 is Morden — the Upper Morden conservation area and the interwar St Helier estate fringe. Much of the suburban stock keeps permitted development rights for rear extensions and lofts, making it one of Merton's more feasible districts, with conservation designation the exception to check for.
Location data: postcodes.io · Constraints: planning.data.gov.uk (borough-level) · Open Government Licence
Constraint context · Merton
Real · planning.data.gov.ukMerton has 28 designated conservation areas and 0 Article 4 areas. A district is too coarse to say which apply to your house — postcode districts span many streets and SM4 crosses 2 boroughs. Enter a full postcode below for the point-level check, or read the full borough picture on the Merton planning guide.
Is SM4 in a conservation area?
Partly — and which part matters. A postcode district is never uniformly designated: SM4 contains 2 conservation areas within 1km of its centre, and whether your own property sits inside one decides whether permitted development survives. The centre point of SM4 itself falls inside Upper Morden.
| Upper Morden | At the centre |
| Wandle Valley | Nearby |
Conservation areas whose official geometry lies within 1km of the centre of SM4. Source: planning.data.gov.uk · Open Government Licence. Proximity to the district centre is not a statement about your own address — run the address check for that.
Does an Article 4 direction apply in SM4?
The national dataset holds no Article 4 geometry within 1km of the centre of SM4. Treat that as unknown, not as “none”. The national dataset is known to omit property-specific directions, so the only safe answer is to verify on the council's own register for Merton before assuming a permitted-development right still exists.
Every designation in the borough: Merton planning guide →
Do you need planning permission in SM4?
Three routes exist, and which one you are on is decided by your address, not your postcode district:
| Permitted development — no application. The work stays inside the GPDO limits and no designation removes them. A Lawful Development Certificate is cheap proof for a future buyer. | No permission |
| Prior approval — the larger single-storey rear extension route, with neighbour consultation. Not available on designated land. | 42 days |
| Full householder application — required once a designation removes your permitted-development right, or the scheme exceeds the limits. | 8 weeks |
SM4 contains mapped conservation-area or Article 4 geometry, so a meaningful share of its streets will have lost some permitted-development rights — which pushes those properties onto the full-application route. Whether yours is one of them is an address-level question, not a district-level one.
What does planning permission cost in SM4?
| Householder planning application | £548 (from 1 April 2026) |
| Lawful Development Certificate — proposed works | £274 (half the application fee) |
| Lawful Development Certificate — existing works | £548 (the full application fee) |
| Listed building consent | No fee |
| Resubmission after a refusal | Free once, within 12 months of the decision |
National statutory figures for England — councils do not set them, so they are the same in every borough. Planning fees re-index every 1 April; confirm the current amount on the Planning Portal fee calculator before you apply. These are the council's fees only — drawings, surveys and any specialist reports are separate.
How long does it take?
| Householder application — statutory target | 8 weeks |
| Householder application — in practice | 8–12 weeks |
| Prior approval (larger home extension) | 42 days |
| Lawful Development Certificate | 8 weeks |
| Householder appeal — deadline to lodge | 12 weeks from the decision date |
| Householder appeal — typical decision | Around 18 weeks |
What if it's refused?
A refusal is a decision notice with reasons attached, and those reasons are a roadmap. Most homeowners in Merton — as anywhere in England — are better served by amending the scheme and using the free resubmission than by appealing: you get one further application on the same site within 12 months without paying again.
| Who can appeal | The applicant only — not neighbours |
| Fee to appeal | None — you bear your own costs |
| Procedure | Written representations for most householder appeals |
| Success rate | Roughly a third — about 36% of householder appeals allowed in 2025/26 |
Appeals go to the Planning Inspectorate, an independent national body. How to read a refusal and choose your route →
Planning permission by project in Merton
Terraces in Colliers Wood, South Wimbledon and Mitcham extend under PD; the John Innes and Wimbledon conservation areas need a full application.
Rear extension in Merton →Deep precedent on the Wimbledon and South Wimbledon terraces; the John Innes Article 4 areas need a full application.
Side return extension in Merton →Common across Wimbledon, Colliers Wood and Morden; the John Innes and Wimbledon conservation areas decide dormer form via a full application.
Loft conversion in Merton →Permission and a structural and ground-condition case are expected, with the John Innes and Wimbledon conservation areas adding heritage scrutiny.
Basement extension in Merton →Workable under PD on many plots; the John Innes and Wimbledon conservation areas can remove outbuilding PD rights — verify the address.
Garden room in Merton →Pinpoint your street
More of Merton
Planning Permission Checker provides planning and cost intelligence for early feasibility only. It is not legal, planning, valuation, architectural, structural, or surveying advice. All estimates are indicative and must be verified by qualified professionals before purchase, design, planning submission, or construction.
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