Velux loft conversions in London: rooflights, no dormer

Published London guides for 2026 put a Velux or rooflight conversion at £30,000–£55,000. That is the median of several companies' ranges, not our quote; the sources disagree on what a basic conversion includes, and some quote with VAT while others do not. Building control fees, any party wall surveyor and the decoration below come on top. Our loft conversion cost guide lists the sources, and the same page shows why a dormer starts at £55,000.

A Velux conversion is the only type where that figure is even close, and in London at 2026 prices the published range still starts at £30,000. The advertised starting prices below that describe a floor, a rooflight and a ladder, without the stair, the fire doors on the floors below or the insulation to current standards; the loft conversion cost guide sets out what each type costs and why, and boarding a loft for storage is the honest use of a smaller budget.

Since 25 April 2024, building work done without planning permission in England becomes immune from enforcement only after ten years; work substantially completed before that date keeps the old four-year limit (gov.uk planning enforcement guidance, checked September 2026), so check the position with your council. A rooflight conversion rarely needs planning permission anyway, so the rule seldom applies to it; Building Regulations approval is the requirement that matters here, and it has no time limit for a conversion that was never inspected. Our loft conversion cost guide covers the rule in full.

Usually not on a house. Rooflights that project no more than 150 millimetres from the roof surface and sit below the ridge are permitted development, including on the front slope, and side-facing ones simply have to be obscure-glazed and non-opening below 1.7 metres. Conservation areas and Article 4 directions can restrict rooflights on the street-facing slope, listed buildings need consent for any of them, and flats have no permitted development rights (Planning Portal, loft conversions, checked September 2026; confirm with your borough). We check the address before recommending positions.

More than for any other type. About 2.2 metres from the top of the ceiling joists to the underside of the ridge is the working minimum for a loft conversion, and a rooflight conversion needs comfortably above it, because the new floor, insulation and plasterboard take around 300 millimetres and the slope stays on both sides. Steep Victorian and Edwardian roofs often have it; shallow 1930s and trussed roofs usually do not, and there a dormer is the honest answer.

If the roof is tall, a Velux conversion is the best value loft there is: no roof structure, no cladding, usually no planning, and the least disruption. If the standing area under the ridge would be a narrow strip, it is money spent on a room you cannot furnish, and a dormer at £55,000–£80,000 in the published London ranges buys a bedroom you can stand up in across most of its floor. We measure and tell you which applies before drawing anything.

Yes, whether or not planning permission is needed. The new floor, the trimming of the rafters for the rooflights, insulation, the stair, ventilation and the fire strategy for the whole house are all controlled, and the work is inspected as it proceeds. Fitting a rooflight into an existing roof without converting the loft is a smaller matter, but the moment there is a floor and a stair it is a conversion, and the completion certificate is what makes it a room.

With no roof structure to build and usually no planning application, the building control submission is normally the only approval in front of the start; where the steels bear on a party wall, the two-month notice period runs first, so we serve notices at design stage. On site it is the shortest loft programme, because the roof is never opened and the weather rarely delays it, and a small shower room or a trussed roof that needs extra steel adds to it. We give the on-site programme for your roof with the quotation.

Yes, if it is built as one: a structural floor, a stair with compliant headroom, fire doors and alarms making the stairwell a protected route, insulation to current standards and a building control completion certificate at the end. A loft reached by a ladder, or a floor laid on the old ceiling joists, is storage whatever furniture is in it. Estate agents and surveyors describe rooms by their paperwork, not their bed.

Usually, and it is a common second step. The floor, the stair and the fire protection are already there, so the later job is the dormer structure itself: the rear slope is opened, the box framed and clad, and the room replanned around the new flat ceiling. Steels sized for the first conversion may need checking for the added weight, and party wall notices apply again. It costs more in total than building the dormer first, but it lets the budget arrive in two parts.