Dormer loft conversion drawings in Wandsworth

The permitted development limits we design to

Outside conservation areas, a dormer on a Wandsworth terrace or semi can often be built under the national rules. On volume: 40 m³ (terrace house) / 50 m³ (any other house) additional roof volume. On position: No enlargement beyond the plane of a roof slope that forms the principal elevation and fronts a highway.

On the set-back from the eaves: Original eaves maintained; enlargement set at least 0.2 m from the eaves measured up the roof slope, so far as practicable (not required for hip-to-gable or roofs joining a rear/side extension). On materials: Exterior materials similar in appearance to the existing house.

On a terrace house the volume allowance is the smaller one, and a full-width rear dormer can use most of it, which is why we calculate before we sketch.

Planning applications and the borough's record

When the dormer needs permission, the application is a householder one. Wandsworth decided 977 householder applications in its latest year, granted 91.9 per cent, and decided 92.4 per cent in time.

Those figures are for every kind of householder project, so they say nothing certain about a dormer. We use them to plan the timetable, and rely on the drawings to make the case: the dormer is dimensioned against the roof, so the officer can see how it sits.

If you would rather prove a permitted dormer than apply, a Lawful Development Certificate in Wandsworth gives written confirmation.

Side windows, stairs and fire protection

A dormer cheek that faces a neighbour carries a condition: Upper-floor side windows obscure-glazed and non-opening below 1.7 m above floor.

A loft that cannot reach full stair headroom has a reduced standard: Loft conversions where 2.0 m cannot be achieved: 1.9 m at the centre of the stair, 1.8 m at the side (half width). Where the work adds a new storey, fire protection is also required: New storey above 4.5 m by loft conversion: protect the full escape route with fire-resisting doors (min E 20) and partitions (min REI 30). The new roof must meet an energy standard too: 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.

We put those on the drawings, and our building regulations drawings in Wandsworth take the detail through to construction.

Surveying a Wandsworth roof before the dormer is drawn

Wandsworth adopted its Wandsworth Local Plan 2023-2038 in 2,023, so the policies an officer applies to a dormer are recent. They sit behind the Housing SPD, which deals with roof extensions and loft conversions together with rear extensions and basements.

Roofs differ from house to house even on one street. Ridge height, rafter depth, chimney breasts and party walls all change what a dormer can do, so a drawing copied from a neighbour is a weak guide. Our survey records your roof on one datum with the floors below.

That record shows how much volume a dormer can add, where the stair lands and what the structure needs. It also gives the engineer accurate figures for the steel at the dormer opening, which keeps the later construction drawings consistent with the planning set.

Price, checking and related drawings

A dormer set starts at £695 including VAT, fixed in advance. A second chartered technologist checks every sheet before submission. If the council asks for changes we redraw at no charge.

For other roof forms see loft conversion drawings in Wandsworth, Velux loft conversion drawings in Wandsworth and L-shaped dormer drawings in Wandsworth. The borough overview is at architectural drawings in Wandsworth. Next door, compare Lambeth and Merton, or read the national guide on our dormer loft conversion drawings page.