Loft Projects Designed for South West London

Lambeth's Design Guide describes the London roof as two pitches set front to back behind a parapet, falling to a central valley that drains to the rear, so it can hardly be seen from the street. It is common on Lambeth buildings of the early and mid-19th century.

Lambeth will not accept the loss of a London roof on a heritage asset or on a building in a conservation area. Elsewhere it supports replacing one only with a traditional full mansard built to its guidance, which, where no adjoining historic example sets the pattern, means two 70 degree lower slopes, two 30 degree upper slopes and an internal head height of 2.1m.

Wandsworth's 2016 Housing SPD calls the London or butterfly roof incapable of adaptation, so a loft scheme on one effectively means building a completely new roof.

On such a house we treat the loft as a new roof from the outset, surveying parapet, valley gutter and rear drainage before drawing any rooms.

Sources: Lambeth Design Guide SPD Part 4: Building Alterations, Extensions and Retrofit (August 2023), Wandsworth Council: Housing Supplementary Planning Document (adopted November 2016), Alterations to Roofs and Loft Conversions

In conservation areas, Wandsworth's SPD says hipped roofs on semi-detached pairs and terrace ends must be kept. More generally, turning the hip into a gable on one half of an unaltered pair is unlikely to be supported, and the SPD suggests a well proportioned dormer on the side slope instead.

Lambeth does not accept the loss of hipped roofs on heritage assets or in conservation areas, and on clay-tiled houses it resists a full hip-to-gable conversion in favour of a half-hip.

Front slopes are treated with caution. Wandsworth describes alterations to the front of houses as rarely acceptable, and will not accept raising a terraced house's ridge to steepen its front pitch where the slope would then differ from the neighbours.

In 2025 Wandsworth approved, with conditions, a scheme for a house on Gassiot Road in Tooting Bec that combined a rear dormer and two front rooflights with a rear and side extension.

Sources: Wandsworth Council: Housing Supplementary Planning Document (adopted November 2016), Alterations to Roofs and Loft Conversions, Lambeth Design Guide SPD Part 4: Building Alterations, Extensions and Retrofit (August 2023), Wandsworth Planning Explorer — application 2024/4226

Hammersmith and Fulham has 44 conservation areas covering about half the borough, and some permitted development rights are restricted inside them. Its list of properties without permitted development rights names flats, maisonettes and houses in multiple occupation, conservation area properties, listed buildings and homes whose rights were removed by a planning condition.

Where a house does qualify, the Planning Portal limits the added roof volume, counting earlier enlargements, to 40 cubic metres for a terraced home and 50 for any other house. Side-facing windows must be obscure-glazed and, if they open, be 1.7 metres above the floor of the room.

Richmond's application guidance names loft conversions among works that may need permission and warns that Article 4 directions can remove permitted development rights.

Sources: LBHF - Conservation areas, LBHF - Permitted development rights, Planning Portal: Loft conversion, planning permission, Richmond Council — make a planning application

Wandsworth's SPD warns that because a new structural floor and roof have to be built, finished headroom ends up about 300mm lower than the loft has today. It also sets out the stair headroom the Building Regulations look for: generally 2.00m, which can fall to 1.90m on the centre line of the flight at pinch points, provided one side keeps 2.00m and the other at least 1.80m.

The Planning Portal points out that the joists forming a loft floor in most homes were never intended to bear a significant load, and that any wall picking up new floor joists has to run down through the house to its foundation or else receive adequate support part-way.

GOV.UK says silence after a party wall notice is not agreement; the dispute process starts once the response period passes. Kensington and Chelsea's construction code adds that vibration damage next door, even cracked plasterwork, may be covered by a party wall agreement.

Neighbouring boroughs keep different site hours. Hammersmith and Fulham tries to keep noisy work within 8am to 6pm on Monday to Friday plus Saturday until 1pm; Kensington and Chelsea allows work audible beyond the site on Monday to Friday between 8am and 6pm, and none at weekends without written permission.

Kensington and Chelsea also requires a council licence before any scaffold, hoarding, skip or mobile crane goes on the highway, and issues no weekend or bank holiday parking suspensions unless a construction traffic management plan provides for them.

Electrical and gas work is carried out by appropriately registered engineers.

Sources: Wandsworth Council: Housing Supplementary Planning Document (adopted November 2016), Alterations to Roofs and Loft Conversions, Planning Portal: Is building regulations approval needed for a loft conversion?, Planning Portal: Loft conversion, building regulations: existing walls and foundations, GOV.UK - Party walls and building work, Royal Borough of Kensington and Chelsea: Code of Construction Practice, LBHF - Construction site noise and dust pollution, Royal Borough of Kensington and Chelsea: construction site enforcement, Royal Borough of Kensington and Chelsea: Code of Construction Practice (April 2019)