Lawful Development Certificate in Westminster

Roofs, mews and the council's own guidance

Westminster publishes two guides that shape its planning decisions: Roofs: a guide to alterations and extensions on domestic buildings SPG and Mews: a guide to alterations SPG. The first covers roof alterations and the second covers mews houses.

Those guides apply to planning applications. A certificate is tested on the Order only, so a mews house that sits outside every restriction can use its householder rights without the guide. We draw for both routes and keep the sheets consistent.

The council's local plan, the City Plan 2019-2040 (2026), is the policy basis for any application that follows.

Flats and whole houses

If your home is a flat the rule is firm: Householder permitted development (Sch 2 Part 1) does not apply to flats or buildings containing flats. So for a flat the question is not a certificate but an application, and our planning drawings in Westminster are drawn for that.

For a whole house, the limits are national. A rear extension is: 3 m (attached) / 4 m (detached) beyond the original rear wall, single storey. A roof enlargement uses a volume allowance: 40 m³ (terrace house) / 50 m³ (any other house) additional roof volume.

Westminster's decision record

Westminster recorded 138 certificate applications in its latest return. On householder planning applications it decided 366 cases, granted 82 per cent and decided 79 per cent in time.

These are figures for planning applications, not certificates. We use them only to set expectations on timing. A certificate has its own period of 8 weeks.

Timing matters more here than the numbers suggest. A builder who has been booked before the certificate is issued carries the risk, so we advise owners to confirm the start date only once the decision is in. The drawings are prepared so that a query can be answered quickly.

Surveying roofs, mews and rear additions

City Plan 2,026 is the policy base for any application, and the borough's roofs and mews guides sit beneath it. For a certificate none of that applies, but we read it so the same drawings can be used if the Order turns out not to cover your plan.

On a small mews plot the curtilage cap is the limit to watch: Buildings (other than the original house) may not cover more than 50% of the curtilage. We total existing and proposed buildings on one sheet.

On a larger house with a back addition, the two-storey test is the one to watch: Over one storey: max 3 m beyond the original rear wall and not within 7 m of the rear boundary.

Our survey records the roof, the rear elevation and the garden together. That lets us tell you, before you pay for a full set, which route the plans can support.

Fee, routes and neighbours

The council's fee is: Half the normal planning fee (householder: £274). Our fixed fee includes a second chartered technologist's check on every sheet.

For the borough overview see architectural drawings in Westminster. Where a project falls outside the Order, planning appeals in Westminster and prior approval in Westminster are the routes to know. Nearby, compare Kensington and Chelsea and Camden, or read the national guide on our Lawful Development Certificate page.