Most Wandsworth lofts start from one of two roofs. On the Victorian terraces between the Commons, in Tooting and in Putney, and on the Edwardian terraces of the Southfields Grid and Earlsfield, party walls usually run up through the roof, which is the setting the council's Housing SPD treats most readily for a full-width rear mansard. On the Edwardian semis and the larger houses around Putney Heath and Wandsworth Common, the sides and hips of the roof show from the street, so the project is more likely to be a modest rear or side dormer. The SPD separates these cases closely, so the first job is to read your own roof against it.
The permitted development rules for loft conversions
A loft conversion with a rear dormer is permitted development on a house if the added roof volume is no more than 40 m³ on a terraced house or 50 m³ on a semi-detached or detached house, the dormer sits at least 200 mm back from the eaves and no higher than the ridge, there is no dormer on the roof slope facing the road, materials are similar in appearance, and side windows are obscure-glazed.
Flats and maisonettes have no permitted development rights, so a loft to a top-floor flat always needs planning permission. Full-width box dormers that reach the ridge, and hip-to-gable conversions on semis whose volume exceeds 50 m³, also fall outside the allowance.
What changes in Wandsworth
Roof extensions are not permitted development in a conservation area, so a dormer or hip-to-gable there needs a householder planning application designed to the area's appraisal.
The local constraints that most often decide the route in Wandsworth are listed below, taken from our Wandsworth area page. Each one is a reason to confirm the address on Wandsworth's constraints map before relying on permitted development.
- Conservation areas. Wandsworth has numerous conservation areas, including large ones covering the streets between Wandsworth and Clapham Commons, Putney, Tooting Bec, Wandsworth Common and Nightingale Lane. Source
- Article 4 directions. A number of Wandsworth conservation areas carry Article 4 directions removing permitted development for front alterations, windows, porches and boundary treatments.
- Thames and Wandle flood zones. Battersea, Nine Elms, Wandsworth Town and Putney riverside fall within Thames Flood Zones 2 and 3, and the Wandle corridor through Earlsfield and Summerstown adds further flood risk. Source
- Metropolitan Open Land. Wandsworth Common, Clapham Common, Tooting Common, Putney Heath and Wimbledon Park are Metropolitan Open Land.
What the Housing SPD says about mansards and rear dormers
Wandsworth's Housing SPD, adopted in November 2016, says the rear roof of a mid-terraced house is the part least visible from the street and often the best opportunity for a substantial loft, especially on Victorian and Edwardian terraces where party walls rise through the roof. Its simplest form is to extend the party walls up and span the full width of the house, finished with an outward-facing mansard-style steep slope and a flat roof on top, lit by traditionally detailed dormers projecting from the steep slope. It says a vertical rear face should normally be avoided because the extra bulk is more overbearing on the neighbours, and its illustration shows a 70-degree pitch on a mid-terrace. It also recommends extended party walls in 225 mm brickwork.
Where a terrace sits under one long unbroken roof with no party walls through it, the SPD says a full-width extension between newly built party walls is not appropriate, because they would show at the front above an unbroken ridge. It points instead to a simple rear dormer set below the ridge, above the eaves and in from the boundary at each side. It adds that a true mansard is rare in the borough and is unlikely to be accepted where it is visible from public areas in a conservation area.
Corner houses, semis and the front roof slope
For end-of-terrace and corner houses the SPD says a rear mansard should be avoided, because it changes the shape of a gable end that is clearly visible from the street. It recommends a well-proportioned, traditionally detailed rear dormer, set lower than the ridge and far enough in from the edge to keep the gable end intact. On a semi-detached pair it says changing a hipped roof to a gable on one half of an unaltered pair is unlikely to be supported, and suggests a dormer on the side slope instead. On detached houses it says hipped roofs should always be kept unless there are exceptional circumstances, especially in conservation areas.
The SPD describes alterations to a front roof slope as rarely acceptable, and says new front dormers on houses of uniform design are generally not welcomed. It does not accept raising the ridge to make a terrace roof steeper than its neighbours. Where the surrounding roofs have not been altered, for example a terrace of London roofs behind a parapet, it says the council may consider the location inappropriate for roof extensions, and that a neighbour's poor alteration is not a reason to repeat it.
What Wandsworth planning officers look for
Rear extensions deeper than neighbouring precedent, side-return infills with parapets above the neighbour's fence line and roof extensions in conservation areas are the common refusal reasons. Mansard lofts are widely accepted on terraces where they match a pattern already established on the street, but front dormers are resisted. Pre-application advice is available for a fee.
Fees and timelines
Wandsworth decides a householder application or a Lawful Development Certificate within 8 weeks of validation. The council fee is £528 for a householder application and £264 for a Lawful Development Certificate (England, from 1 April 2025; verify before applying).
Our own fee is fixed once quoted. The quote tool gives an indicative figure in minutes and a written quote follows within 24 hours.
Primary sources
- Wandsworth Council, Housing SPD (adopted November 2016), alterations to roofs and loft conversions
- Wandsworth Council, conservation areas frequently asked questions
- Wandsworth Council, Shaftesbury Park Estate Conservation Area Article 4 direction
- The Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2: the permitted development limits quoted above.
- Planning Portal: do you need permission: the national guidance and the application service every council accepts.
- London Borough of Wandsworth: planning: the council's own constraints map, validation checklist and pre-application service.
