Dormer loft conversion drawings in Hillingdon

Article 4, conservation areas and trees in Hillingdon

Hillingdon has 33 conservation areas and 150 Article 4 directions. Class B roof enlargements are not permitted development on article 2(3) land, and a direction can remove rights elsewhere.

There are also 731 tree preservation orders. They rarely affect a roof, but scaffolding and access can, so we note them on site checks.

Historic England lists 436 entries in the borough, which adds a separate consent for any listed house.

Green belt and the shape of Hillingdon housing

About 42 per cent of Hillingdon is green belt, and 68.9 per cent of its 109,228 households live in houses. We check the roof form of each house on the survey, because it decides how a rear dormer can sit.

Hillingdon's householder record

Hillingdon decided 1,147 householder applications in its latest year, and granted 90.2 per cent. 94.3 per cent were decided in time. These cover every home project, so they guide our timing advice only.

Permitted development for a Hillingdon dormer

Outside conservation areas and directions, an unlisted house can use permitted development within 40 m³ (terrace house) / 50 m³ (any other house) additional roof volume. No enlargement beyond the plane of a roof slope that forms the principal elevation and fronts a highway.

The council's two-thirds width test is a planning rule, so we still draw to it where an application is needed.

Measuring the original roof width in Hillingdon

Because the council's width test refers to the original roof, we need to establish what the original roof was. On houses that already have an extension, we trace the original ridge and eaves lines from the survey, and from historic maps and photographs where they exist.

We then take two thirds of that width and draw the dormer to fit within it. The calculation is on the drawing, so that you, the engineer and the council all work from one figure.

Where an earlier dormer already exists, we say so at the outset, since the council's test is about the roof as it began, not as it is now.

Materials, side windows and the stair in Hillingdon

The permitted development rule for finishes is: Exterior materials similar in appearance to the existing house. In a conservation area, or on a listed house, the council asks for traditional rear dormers, which usually means tile hanging or lead.

Side windows follow this rule: Upper-floor side windows obscure-glazed and non-opening below 1.7 m above floor.

The stair and escape route fall under building regulations: 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), and 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).

What we check on a Hillingdon address before quoting

Hillingdon is a long borough with very different streets in its north and south, so we start with the address. We check it against the Article 4 list, the conservation areas and the green belt, and note any tree preservation order near the house.

The borough also has 5 scheduled monuments and 45 Heritage at Risk entries, which matter more to a house beside one. With photographs and the survey we can say which route fits, and what size of dormer the policy will allow.

Hillingdon dormer drawings and related pages

Each set has plans, a section and four elevations. Price: £695. If the council asks for changes, we redraw at no charge until approval.

See loft conversion drawings in Hillingdon, house extension drawings in Hillingdon and architectural drawings in Hillingdon. Nearby are Ealing and Hounslow.