Does an electric rooflight need an electrician?

The answer starts with what drives the opening. A mains unit has an actuator wired back to the house. A low-voltage unit has a transformer that steps the supply down, and the short cable from transformer to motor is the low-voltage part. A solar unit charges a battery from a small panel on the glass.

Part P of the Building Regulations requires electrical work in a dwelling to be designed, installed and tested so that it protects people from fire and shock. Some work is notifiable, such as a new circuit, and some is minor, such as an extension to an existing circuit outside the rooms with extra rules. Which side a rooflight feed falls on depends on the circuit it comes from and the room it serves, and the electrician tells you.

Ask the electrician early whether the feed will be a spur from an existing circuit or a circuit of its own, because that choice decides how much of the house wiring is touched and what paperwork follows. A new circuit means a free way in the consumer unit, which is why we ask for a photo of it. A spur is shorter, though it must suit the load on the circuit it joins.

A rooflight over a bath or shower sits in a damp room, so the electrician decides where the cable and the switch can go. An electrician registered with a competent person scheme can notify notifiable work personally. Otherwise it goes through Building Control, which is a separate route from the one for the roof opening.

A low-voltage motor is gentler to work around. The cable from transformer to actuator carries a small current, so it can be clipped along a rafter and slipped behind the lining without much chasing. The transformer sits somewhere dry, such as a cupboard or a boarded corner of the loft, and takes its own mains feed, so the electrician is still needed for that one connection.

A solar unit suits a pitched slope that faces the sky, where the panel can charge. It spares you the cable route altogether, which helps in a finished bathroom or a room with a vaulted ceiling. The trade-off is that a battery sits in the system, and in a shaded position the panel may charge slowly. We look at the aspect of the slope before suggesting it.

The two trades overlap in the loft void and the ceiling below it. We make the opening, fit the unit and plan where the cable will run and the switch will sit. Doing that before the lining is boarded keeps the cable out of the plaster. In a garage conversion that is still half built, the electrician can lay conduit before the ceiling goes up, which spares you opening it again.

On a flat roof the cable passes through the build-up and has to be sealed where it comes through, a detail the roof side of the job settles. Whichever roof it is, the unit itself still has to meet the Part L limits: 1.4 W/m²K (or Window Energy Rating band B) for a roof window, or 2.2 W/m²K for a rooflight. We handle the Building Control notification for the roof work where it is notifiable. The cable and control options are laid out in wiring and controls for an electric rooflight, and the electric opening rooflights page covers the units.

If the ceiling is already plastered, the loft side matters most: a clear hatch, a boarded path to the rooflight position and a light to work by let the cable be laid without lifting a single board indoors. In a bungalow with a shallow roof void the route may need a little more thought, and we look at that with you.