Short answer
In Wales, the Building Regulations treat installing a roof window as building work, so they apply to it. Where the work is notifiable, we handle the Building Regulations notification with local authority building control or a registered building control approver. Planning permission is a separate question with its own rules.
- 10-year workmanship guarantee
- We handle the Building Control notification where notifiable
Why a window in the roof is building work
The Building Regulations 2010 treat the provision of a controlled fitting as building work. A fitting is controlled when one of the regulations' parts places a requirement on it, and the Welsh guidance lists windows, roof windows and rooflights among them. A roof window qualifies, so a new unit is covered. Rules that apply to a VELUX unit alone are set out in the guide to VELUX-specific rules.
Swapping an old roof window for a matching new one is still building work, while repairing one is not. Changing just the glass, with the frame left in place, sits outside the energy rules' idea of building work. For a new rooflight, as opposed to a roof window, Building Regulations approval is generally needed, according to the Welsh Government's page on rooflights in the roof.
What the Welsh guidance looks at
Approved Document L (Wales) is guidance on the energy side. It says a new or replacement roof window should have a U-value no worse than 1.4 W/m²K, or a Window Energy Rating of Band B. Fitted units should also be well fitted and reasonably draught-proof.
Ventilation is the next check. Approved Document F says a replacement window should leave ventilation in the home no worse than it was before. If trickle vents were fitted to the old window, the new one should carry vents at least as big, with control left to the occupant or handled automatically. Every habitable room also needs purge ventilation, a means of airing it rapidly, which an opening window can give, whether it is hinged or pivoting. Windows that open less than 15 degrees do not count towards that. The Welsh Government's list of Approved Documents is where the full text sits.
Escape windows and glass safety
A loft bedroom needs a way out. Under Approved Document B (Wales), an emergency escape window must have an unobstructed opening of at least 0.33 m², at least 450 mm high and 450 mm wide, with the bottom of the opening no more than 1,100 mm above the floor. It must let the person reach a place free from danger from fire, and it should stay open without being held.
In a roof window the bottom of the opening may be 600 mm above the floor, instead of the usual 800 mm guarding height. Converting a two-storey house's loft into a room will normally mean fire-resisting doors and partitions, where none existed before, protecting the stairway all the way down.
Glazing safety in Wales is dealt with in Approved Document N. Its critical locations are between floor level and 800 mm in internal and external walls and partitions, and between floor level and 1,500 mm in a door or a side panel close to either edge of a door.
Who checks the work
There are two kinds of building control body in Wales: the local authority building control service, and a private registered building control approver. The choice between them is yours.
Private firms are registered with the Building Safety Regulator, whereas local authority building control answers to the Welsh Ministers. The people who check the work are registered building inspectors, or work to their advice. A private firm of that kind is a registered building control approver. The Welsh Government's page on the building control profession explains how that divides.
Two separate permissions
Approval under one set of rules does not stand in for the other. A roof window can be permitted development on a house when it sticks out no more than 150 mm from the plane of the original roof slope and sits no higher than the highest part of the original roof. Where the house stands inside a conservation area, an AONB, a National Park or a World Heritage Site, a planning application is needed. Flats have no householder permitted development rights.
Our roof window planning page and the planning guide for Wales take that further. For the wider rules, see Building Regulations for skylights in Wales.
Roof lights are a separate case
A rooflight on a kerb is not the same as a roof window in the slope, and the Welsh energy guidance gives it its own limit, a U-value no worse than 2.2 W/m²K. If your plan is flat glass rather than a window, read flat rooflights and Building Regulations in Wales.
What happens at the survey
The free survey covers the roof, the room and the route through the house, and we say which of these rules bear on your job. A fixed written quote follows. You can book through the survey form or send photographs on WhatsApp on 07880 284133 first. For what the work costs, see the price of a roof window.