How much does a skylight cost to fit?

The word covers more than one thing, and the price follows the product. Approved Document L (Wales) separates a roof window, which sits in the same plane as the roof around it, from a rooflight, which is a glazed unit raised on a kerb or upstand. It adds that a rooflight is sometimes called a skylight. A lantern stands up from a flat roof as a glazed structure of its own, and a sun tunnel runs a tube from a roof dome to the room below.

So a fixed window over a landing, a pair of opening units in a loft, a rooflight over a utility room and a lantern on an extension are four separate jobs. Each has a page of its own: roof windows, flat roof rooflights, roof lanterns and sun tunnels. For one product in detail, read the answers on roof windows, flat roof skylights, lanterns and sun tunnels.

On a pitched roof the window is flashed into the tiles or slates around it. On a flat roof the unit stands on a raised frame, and the surface beside it has to fall away so that water has somewhere to go.

Pitch narrows the choice before price does. VELUX makes a flat roof dome for shallow pitches, up to 15 degrees, and a separate low-pitch roof window meant for 10 to 20 degrees. A roof outside the range of the product you had in mind points to another product, and another figure.

The covering around the opening matters as well. A flat roof surface in poor condition changes what the job involves, and the survey looks at it along with the joists underneath.

Cutting a new opening is the larger piece of work. On gov.wales, a brand-new rooflight is described as needing Building Regulations approval in general. Its reasons: the roof structure is usually changed to make the opening, and it needs to be strong enough for the unit, or reinforced until it is.

Swapping a unit that is already in the roof can leave much of that behind. It works best when the new unit matches the old opening, which is why the size marking matters. The guide to VELUX size codes explains the markings, and the answer on replacing a rooflight covers the swap itself.

Once the product and size are fixed, the specification adds its own choices. VELUX glazing choices take in a coating that makes cleaning easier, laminated safety glass and a rain-noise option, although the window itself limits which of them you can choose. Its flat and curved glass rooflights are offered in double and triple glazing.

Opening units come in manual and electric forms. VELUX fits electric roof windows with a built-in rain sensor that shuts the window once rain starts, which counts for something over a bath or a bed, where nobody wants to climb on a chair as the weather turns.

Energy limits shape the specification too. In an existing Welsh home, a new or replacement roof window should be no worse than 1.4 W/m²K, or Window Energy Rating band B, and a rooflight no worse than 2.2 W/m²K.

A house in Wales can have a rooflight as permitted development when it stands out no more than 150 mm from the original roof slope and is no higher than the highest part of the original roof. Inside a conservation area, the Gower AONB, Bannau Brycheiniog National Park or a World Heritage Site, a new rooflight in the roof slope goes through a planning application instead. For flats and maisonettes, householder permitted development does not apply at all. The skylight planning permission guide gives the conditions in full.

Where the work is notifiable, we handle the Building Regulations notification with local authority building control or a registered building control approver. For the detail, see the Building Regulations guide.

Every factor above has to be judged at the house itself, so the survey comes first and costs nothing. A fixed written quote follows, and our guarantee puts 10 years on the workmanship, in writing. The wider picture of pricing is on the costs page. To book, ring 01792 929062 or send the survey request.