Do electric rooflights need an electrician?

An electric rooflight has a motor or actuator, a control and usually a rain sensor. The window itself is built into the roof by the installer, in the same way as a manual one. The question is what feeds it, and that comes in three forms.

Mains-fed, with a transformer

Many electric windows run from a low-voltage motor, powered through a transformer that plugs into or is wired to the house supply. The low voltage side is relatively simple, but the transformer's connection to the mains is the part that needs care, and it is where the qualified electrician comes in.

Mains-fed, direct

Some actuators and larger lantern vents run at mains voltage. The wiring, the isolation and the protection are all matters for a qualified electrician, and the result is covered by Part P.

Solar-powered

A small panel on the unit charges a battery that runs the motor. There is no cable to the house, so there is no mains work. The unit is still wired internally by the maker, and the control is usually a handset, which keeps the whole system self-contained. See solar-powered rooflights and windows for the trade-offs.

The two jobs meet at the window, so it helps to know where one ends and the other begins.

The installer fits the rooflight, makes it weathertight, forms the lining and finishes the ceiling. We also take the opening to the point where the motor, the cable and the sensor can be fitted, leaving a route for the cable through the roof build and the lining. The electrician provides the supply, the connection point, any isolator and the testing, and signs the work off.

It works best when the two are planned together before the roof is opened. A cable that needs to run through a lath and plaster ceiling, or through a deep cold roof, is much easier to place before the lining is formed than after it has been plastered. That is why the cable route and the position of the control appear in the finish schedule.

Part P covers electrical safety in dwellings. New circuits and work in some locations are notifiable, while minor additions can fall outside the notification. Whether a particular job is notifiable depends on the work, which is why the electrician confirms it for your house and records it properly.

The rooflight itself is separate. Cutting a fresh opening into a roof that already exists needs Building Control approval, since the rafters are altered and the window has to satisfy Part L. A like-for-like swap of the complete unit, frame and glass, is notifiable too, and the notification is something we deal with. Where the electrical side is also notifiable, the electrician's certificate and our paperwork sit side by side, and it is worth keeping both together in a folder for when you sell.

Official guidance on electrical safety is on gov.uk, and the planning side of rooflights is covered at planningportal.co.uk.

Quotes for electric rooflights vary in what they include, so ask directly.

• Who is providing the electrical supply and connection?
• Is it included in the price, or a separate line?
• Where will the cable run, and who makes good the ceiling afterwards?
• Where will the control go, and is that position on the quote?
• Will you receive a certificate for the electrical work?

A quote that says only "electric rooflight" without any of these answers has left a gap that someone will have to fill, usually on the day and usually at extra cost. We write each of these lines down, so you know what is covered before work starts.

The same rule applies when you swap a manual unit for an electric one. A power source that did not exist before has to be provided, and the nearest supply may be a floor away. In a house with a finished loft room or a decorated landing, the cable route is the main variable, and it may be worth choosing a solar model to avoid it. Our answer on whether an existing rooflight can be made electric covers the conversion question.

The cable is the awkward part of most electric installs. From the window, it has to reach a supply somewhere in the house, and the route decides how much disturbance there is. In a loft conversion, it may run in the rafter space and down a stud wall to a spur nearby. Under a flat ceiling with a cold loft above, it can be laid across the joists and dropped to a switch position beside the door.

Lath and plaster ceilings are the hardest, since they crack when channelled carelessly. Where a chase has to cross one, we would rather the route is planned so it is cut once and filled in plaster or lime to match, with the edge feathered in. In a plasterboard ceiling, the board can be lifted, the cable laid and the joint taped and skimmed, so the line does not show when painted.

A wireless control avoids the run to a wall switch, since a handset or a wall-mounted keypad talks to the window by radio. The supply to the motor is still needed, but the control position stops being a wiring question.

Take a look at the room. Where would the nearest socket or junction be? Is the ceiling lath and plaster, plasterboard or something else? Would you rather avoid cable altogether? Those answers decide whether the electrical side is a small job or a larger one. If you would like a view, ask for a quote and send a photo of the room and the loft if there is one. Our page on electric opening rooflights sets out the whole subject, and what happens to an electric rooflight in a power cut deals with the other practical worry.