Velux loft conversion drawings in London

Rooflights under permitted development

Rooflights are the simplest roof alteration in law. The rule is: Roof alterations (e.g. rooflights) may not protrude more than 0.15 m beyond the roof plane. The units therefore sit close to the slope rather than standing proud of it, which is why low-profile rooflights are popular.

Windows in a side slope have their own rule: Side roof-slope windows obscure-glazed and non-opening below 1.7 m.

Where permitted development is not available, a rooflight alteration is still usually a modest application. We run the address check first, then choose between the Lawful Development Certificate route and a householder application through planning drawings.

Getting out: escape windows and fire doors

A habitable room in the roof needs a safe way out, and a rooflight can be that way. The guidance gives the size: Escape window: unobstructed openable area at least 0.33 m², at least 450 mm high and 450 mm wide, bottom of opening no more than 1100 mm above floor.

The position matters as much as the size. The bottom edge cannot be too high, and the window must be reachable, so we set the rooflight height on the section to suit the floor level you will actually have.

A converted loft above a certain height also needs a protected stair: 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). And alarms: All dwellings: fire detection and alarm system minimum Grade D2 Category LD3 (BS 5839-6), mains-operated smoke alarms to BS EN 14604.

Stair headroom without losing a bedroom

The stair is where most Velux conversions are won or lost. The Approved Document allows a reduced standard when full height cannot be reached: 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 stair needs both headroom and floor area, and it usually takes space from the room below. We try the stair in several positions on the model and show the effect on the first floor, so you trade space knowingly rather than discovering it on site.

Steel and joist sizes come from the engineer. We coordinate those through structural calculations so the floor build-up on our section is correct.

Energy: rooflights and the roof

New rooflights are tested for heat loss like any other window: 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. Choose a unit that meets that figure, because a cheap one can fail the building regulations check.

Insulating a sloping roof costs headroom, since every centimetre of insulation comes out of the room. Our drawings show the build-up so you can see how much height remains before work starts.

Our building regulations drawings carry the details forward.

Cost and what you receive

Velux loft conversion drawings start at £695, VAT included, fixed and published before you commit.

You receive existing and proposed plans, elevations and sections that show the rooflights, stair and floor, together with location and block plans. A second MCIAT chartered technologist checks each sheet before it goes anywhere.

If the council asks for changes, we redraw at no charge until approval. If you later want more headroom, a dormer loft conversion is the step up.

Velux conversion drawings by council

Conservation areas and roof guidance vary by borough, so the right design depends on where the house stands. Check your council under architectural drawings by area.

To see every loft type before you choose, read loft conversion drawings, which compares the volume rules and the four conversion shapes.