Velux Loft Conversion: Cost, Time and Planning Permission

What a Velux loft conversion is

A Velux (rooflight) conversion fits windows and ventilators into the existing roofline, with no structural alteration and no added floor space, which makes it the simplest type of loft conversion. The roof keeps its shape, so the room you get is the space already inside it.

Velux loft conversion cost and build time

A Velux conversion and a dormer on the same 30m² loft compare like this, with the work described in Checkatrade’s types guide, the prices from its cost guide and the build times from its timescale guide.

30m² loft	Velux	Dormer
The work	Windows and ventilators fitted into the existing roofline	A box structure with vertical windows
Floor space	None added	Headspace and floor space added
Average cost	£27,500	£50,000
Cost range	£22,500 to £30,000	£40,000 to £60,000
Cost per m²	£920	£1,670
Typical build time	4 to 6 weeks	10 to 12 weeks

A Velux conversion is usually the most affordable type of loft conversion, and a dormer, which adds the headspace and floor space a Velux conversion does not, costs £22,500 more on average on Checkatrade’s figures. How long the build takes also depends on the condition of the loft, its size and the finish, and a fully decorated, furnished room takes longer than a basic shell, Checkatrade’s timescale guide says.

Hidden costs and contingency

Checkatrade’s cost guide lists hidden costs that can add 10 to 15%, among them architect drawings at £1,000 to £2,000 and a bat survey at £400 to £750 where one is required. The same guide says many homeowners plan a contingency of 10 to 15% on top of the quote, and that most builders recommend around 10%.

Head height and roof type for a Velux conversion

A Velux conversion adds no height or floor space, so the loft needs enough of both already. Checkatrade’s suitability guide gives a minimum of 2.2m from the floor to the highest point, to leave at least 1.9m of finished headroom once flooring and insulation go in. When you work out the usable floor area, the same guide says to leave out anywhere the height from the floor to the eaves is under 1.2m, the space for the new stairwell and obstacles such as chimney breasts, and it says a roof pitch over 30 degrees tends to work better.

Checkatrade’s suitability guide calls roof type the biggest factor. Traditional roofs, common in homes built before 1965, have rafters forming an M shape and are generally easier to convert, while trussed roofs, standard after 1965, have rafters forming a W shape and are more complex and costly to convert because the frame typically needs replacing, the same guide says. A trussed roof does not rule a conversion out.

Velux loft conversion planning permission

Rooflights and skylights on a house are permitted development, with no planning application, when they meet the three conditions on the Planning Portal’s roof page, which cover how far they project, how high they sit and how side-facing windows are glazed and opened. Permitted development does not cover a flat or a building containing flats, the Planning Portal’s loft conversion page says.

A dormer changes the shape of the roof, so it needs planning permission unless it stays within the permitted development limits for a loft conversion, which cap the extra roof space at 40 cubic metres on a terraced house and 50 cubic metres on other houses, the Planning Portal says.

In Nottingham, Article 4 Directions remove some permitted development rights from specific properties, mostly within conservation areas, in Devonshire Promenade, Foxhall Road, Sneinton, Strelley Village, Waterloo Promenade and Wellington Terrace. They restrict minor building work, including changes to windows and doors, and the council advises using its Minor Works Enquiry Service before doing work in those six areas.

Building regulations for a Velux loft conversion

Rooflights may need no planning application, but building regulations approval is required to convert a loft into a liveable space. The regulations make sure the new floor is strong enough, the structure and existing roof stay stable, there is safe escape from fire, the stairs are safely designed and sound insulation to the rooms below is reasonable, the Planning Portal says.

The Planning Portal’s stairs guidance says a new stair serving the new room will be needed for fire safety and retractable ladders or stairs are not normally acceptable, though a space saving stair may be possible where there is not enough room for a full traditional stair. On a typical loft conversion of a two-storey house, its fire safety guidance calls for new fire-resisting doors, and sometimes partitions, to protect the stairway, and mains powered, interlinked smoke alarms in the stairway at each level.

Getting quotes for a Velux loft conversion in Nottingham

A quote should price the whole room, so ask every company to cover the same work, from the rooflights and the new floor to the stair, the fire protection and the building regulations fees.

Among the Nottingham loft conversion companies compared for rooflight conversions, Premium Home Conversions in Long Eaton publishes a starting price of £15,000 for a Velux conversion, and Premier Roofing Solutions on Radford Road installs Velux roof windows and skylights with a 10-year Velux warranty. M.R Conversions in Jacksdale fits Velux windows, and the services of XL Lofts in Heanor include truss roof conversions, loft stairs and Velux roof windows.