Loft conversion drawings in London

Choosing the type of loft conversion

We draw four loft shapes, and each has its own page. A Velux loft conversion keeps the roof as it is and adds rooflights. A dormer loft conversion pushes out a box at the back for full headroom. An L-shaped dormer wraps over the outrigger of a Victorian terrace. A hip-to-gable conversion squares off a sloping side.

Roof shape and existing headroom decide which is realistic. A steep Victorian roof with a high ridge may need only rooflights, while a low interwar semi may need a dormer to make a usable room.

We measure the roof on the survey and show you the realistic options in 3D, with the volume of each worked out, before you pick one.

Conservation areas and flats

Permitted development is withdrawn in a lot of London. The rule is clear: Class B roof enlargements are not permitted development on article 2(3) land. So a roof extension in a conservation area, or on a flat, needs a planning application.

A rooflight is treated differently, and some alterations are allowed even where a dormer is not. That is why our first step is to check the address for conservation areas, listing, Article 4 directions, trees and planning history, and then tell you which of the loft types is open to you.

If an application is needed, it runs through planning drawings, and a Lawful Development Certificate confirms the permitted route when you qualify.

Stairs, headroom and fire safety

A loft conversion is judged by building control on how people get up and out. For the stair, the rule allows a concession: 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).

A new storey over a certain height also needs a protected escape route. The guidance says: 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). Fire doors on the landing and stair are a normal part of the specification, and they shape where the stair can land.

Alarms are covered too: All dwellings: fire detection and alarm system minimum Grade D2 Category LD3 (BS 5839-6), mains-operated smoke alarms to BS EN 14604.

These rules are why stair position is the first thing we settle with you. A stair that costs a bedroom below can ruin a loft that otherwise works, so we try several positions on the model.

Roof insulation and the building regulations package

The new roof is a new element in an existing home, with its own limit: 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. In a thin roof, hitting that figure takes careful build-up thickness, and it affects the final ceiling height.

The engineer sizes the steel and floor joists. We coordinate the sizes with the drawings through structural calculations, then carry the details into our building regulations drawings.

If the roof adjoins a shared wall, party wall notices may be required, and we prepare them through party wall notices.

What loft conversion drawings cost

Loft conversion drawings start at £695, VAT included, for Velux or dormer designs, fixed and published before you commit. Hip-to-gable and L-shaped dormers are quoted after a free constraints check.

You receive existing and proposed plans, elevations and sections, location and block plans, and submission if you want it. A second MCIAT chartered technologist checks every sheet before it leaves us.

If the council asks for changes, we redraw at no charge until approval. Drawings are normally ready about a week after the survey.

Loft conversion drawings by borough

Councils apply the same national rules through different local guidance, and conservation areas vary hugely between boroughs. Loft conversion drawings in Camden show how a borough page sets out the local picture.

To find your council, browse architectural drawings by area. Planning a ground-floor extension too? See house extension drawings.