Dormer loft conversion drawings in Hammersmith and Fulham

A borough of flats, and what that means for a dormer

Only 24.6 per cent of the borough's 81,244 households live in a house or bungalow, and 32.1 per cent own their home. Permitted development for roof enlargement applies to houses, not to flats or maisonettes.

A dormer on a flat is therefore an application from the start, and it involves the freeholder. We establish who owns the roof space at the first conversation and say what the freeholder will want to see.

How Hammersmith and Fulham decides householder applications

The council decided 506 householder applications in its latest published year and granted 97.8 per cent. Only 79.8 per cent were decided within eight weeks or an agreed extension, so we advise you to allow generous time for the decision.

These figures cover every householder project and say nothing about any single house. We use them for timing and for expectations, not to predict an outcome.

When a dormer in Hammersmith and Fulham can be permitted development

Outside conservation areas, on an unlisted house, three limits apply. Volume: 40 m³ (terrace house) / 50 m³ (any other house) additional roof volume. Position: No enlargement beyond the plane of a roof slope that forms the principal elevation and fronts a highway.

Set-back is the third: 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). A drawing that meets all three can be confirmed with a Lawful Development Certificate; one that does not goes to the council as householder planning.

Freeholders, neighbours and party walls

In Hammersmith and Fulham the roof is often shared in some way: a freeholder owns the structure above several flats, or a terrace shares a party wall that the dormer will sit against. Either situation changes the paperwork more than the drawing.

A dormer next to a party wall normally calls for notice under the Party Wall etc. Act, which our party wall notices service covers. We prepare the drawings that the neighbour's surveyor will want to see, so the notice can go out with the design rather than after it.

If the freeholder owns the roof, we send them a clear summary of what changes, with the elevation and section, before you make a formal request.

Stairs, fire protection and insulation in a Hammersmith and Fulham dormer

A dormer is only usable if the stair reaches it. Approved Document K allows a reduced height for lofts: 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). We check the position of the new stair on the survey before the dormer is fixed.

The fire rule for a converted loft reads: 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). In older houses, that means work to the existing doors and stair walls.

The new roof elements also have to meet the thermal limits: 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. These feed into the build-up of the dormer roof and cheeks.

What you get and what it costs

The set covers existing and proposed plans, a roof section with the dormer dimensioned, and four elevations. Price: £695. If the council asks for changes, we redraw at no charge until approval.

Looking at the roof as a whole? Read loft conversion drawings in Hammersmith and Fulham. A new back room beneath the dormer is covered by house extension drawings in Hammersmith and Fulham, and architectural drawings in Hammersmith and Fulham gives the borough overview. Neighbours include Kensington and Chelsea and Hounslow.