Rear extension drawings in Westminster

Tree orders and small gardens behind Westminster houses

Westminster has 685 tree preservation orders across 263 mapped zones, and a rear garden here can hold a protected tree whose roots reach into the footprint you are planning. We include a trees check at the start, because a foundation near a protected tree changes both the position and the cost.

Gardens are scarce. Domestic gardens make up only 7.9 per cent of the borough's land, and only 10.2 per cent of households live in a house. If your home is a flat or a maisonette, permitted development for extensions does not apply and the work is a full application.

Heritage: conservation areas, Article 4 and listings

The council publishes 56 conservation areas and 10 Article 4 directions. Historic England lists 4,015 entries inside the borough, including 205 at Grade I, and the borough includes 1 World Heritage Site. A listed house needs separate consent for work to its rear.

Conservation area status does not ban a rear extension, but it narrows the choices. Expect the officer to ask about the rear elevation as seen from other properties, not only from the street.

Prior approval and planning routes in Westminster

National rules let a single-storey rear extension reach 3 m (attached) / 4 m (detached) beyond the original rear wall, single storey on a house without constraints, with a longer reach through prior approval (6 m (attached) / 8 m (detached), single storey, height max 4 m; not on article 2(3) land or an SSSI). The latest twelve months of national statistics show Westminster granting 0 and refusing 0 larger home extension prior approvals, so the route went unused in that period.

A householder application is the usual path, and we prepare it with the heritage and tree information alongside the drawings.

How Westminster decides householder applications

In its latest published year Westminster decided 366 householder applications and granted 82 per cent, and 79 per cent were decided inside eight weeks or an agreed extension. Those are history for the whole borough, not a forecast for your property.

More than a fifth of cases take longer than the eight-week target or an extension, so we advise building time into your programme.

Levy, structure and energy rules for a Westminster extension

Westminster publishes its own levy schedule, the Westminster CIL Charging Schedule, with rates by zone: £811.80/m² (Prime); £590.40/m² (Core); £295.20/m² (Fringe) [schedule rates £550, £400, £200]. On the national side, Residential extensions and annexes can claim exemption (claim before commencement). We note any liability in the handover pack.

The building regulations side is the same everywhere. New elements must meet limiting U-values (New elements in existing dwellings, limiting U-values W/(m²·K): roof 0.15, wall 0.18, floor 0.18, windows 1.4 (or WER Band B), doors 1.4), and glazing should respect this limit: Windows, roof windows, rooflights and doors in an extension should not exceed 25% of the extension floor area plus the area of openings removed or covered. A tall Westminster rear wall with big openings tests that second figure early.

Rear extension drawings for Westminster: the set and the fee

You receive existing and proposed plans, sections and elevations, plus location and block plans, from £695 including VAT, fixed up front. A second chartered technologist checks each sheet. The council's householder fee is £548, paid to it separately, and we redraw free if changes are requested.

Related drawings and nearby councils

For an overview of the borough see architectural drawings in Westminster. Raising the roof as well? Loft conversion drawings in Westminster cover that. Next door, compare Camden and Kensington and Chelsea.