In brief
The cost of fitting a skylight depends on five things: the unit you choose, with its size and glazing; the roof it goes into; any structural work around the opening; access to the roof; and how the inside is finished. Two jobs that look alike from the street can differ a great deal once those are counted, so we price every job from a free survey and give you a written quote.
- The unit: a roof window, flat rooflight, lantern or sun tunnel, and its size and glass
- The roof: tiles, slate or a flat covering, its pitch and its condition
- The structure: rafters or joists to trim, or a kerb to build
- Access: scaffolding, a tower or a lift for heavy glass
- The finish inside: plastered reveals, decorating and any blinds
Why there is no single price
A skylight is a product and a piece of building work at the same time. The product has a price from the maker, which changes with the size, the frame and the glass. The building work depends on your house: what the roof is made of, what holds it up, how high it is and what the room underneath needs. A price that leaves out the building work covers only half of your job.
That is why we price every fitted skylight from a survey of your own roof. We would rather look at the roof, agree the right unit with you and put a figure in writing that covers everything, than give you a number that grows once the tiles come off. The sections below explain what moves the cost, so you can see where your own job sits before we visit.
The unit you choose
Different kinds of skylight sit at very different points on the scale. A standard roof window in a tiled roof is a stock item in common sizes. A flat rooflight is often made to order for the kerb it sits on. A roof lantern is made to measure, with a powder coated frame and several glazed units. A sun tunnel is a different product again, with a small dome on the roof and a reflective tube down to the ceiling.
Within each type, the size and the glass make the biggest difference. Larger units cost more and are heavier to handle. Triple glazing, solar control coatings and self-cleaning glass each add to the price. Opening units cost more than fixed ones, and electric opening with a rain sensor more again. Conservation rooflights, with their slim frames and glazing bars, carry a price that reflects the detail.
We explain the options in plain terms and price the ones that suit the room. If you want to compare two choices, such as a lantern against a large flat rooflight, we can quote both.
The roof it goes into
A tiled pitched roof with easy access is the simplest place to fit a skylight. Slate takes a little longer to open up and make good. Old roofs with lime mortar, lead details or fragile tiles need more care, and a roof that is already failing around the opening may need work before a new unit goes in.
Flat roofs depend on the covering. Fitting into a new roof, while the roofer is laying the membrane, keeps the cost down because the opening, the kerb and the weathering are done once. Cutting into a finished flat roof means opening up the covering and making it good again, which takes time and sometimes a roofer's visit.
Pitch matters too. A shallow tiled roof may need a roof window rated for low pitches, and some need an extra underlay detail. We check the pitch on site and price the right product rather than the cheapest one.
Structure, access and the inside finish
Cutting a hole in a roof means dealing with whatever holds the roof up. In a traditional roof, one or two rafters are usually trimmed and the load carried round the opening. In a roof built with trusses, a truss cannot simply be cut, so the window has to fit between them or an engineer has to design the change. On a flat roof, the joists are trimmed and a kerb built. Each of these is priced from what we find on the survey.
Access can be a large part of the cost. A bungalow roof might need only a tower. A three-storey house in a terrace might need scaffolding with a crash deck, and a heavy lantern might need lifting gear. We tell you in the quote what access we have allowed for and why.
Inside, the opening needs lining and finishing. That can be as simple as a factory lining kit for a roof window, or as involved as boarding, insulating and plastering the reveals of a lantern. If your builder or plasterer is already on site, we agree who does what so you are not paying twice.
Adding a new skylight or replacing an old one
Replacing an existing skylight in the same opening usually involves less work than forming a new one, because the structure is already trimmed and the inside is already finished. The new unit has to suit the opening, though, and an old kerb or frame that has rotted or been built too low can turn a simple swap into a bigger job. We measure the existing opening and kerb, not the old glass, and tell you in the quote whether anything around it needs attention.
How to get a figure you can rely on
Book a free survey. We look at the roof and the room, talk through the options, and send you a written quote that names the unit, its lead time, the access we have allowed and anything that depends on your builder. If your project is at the drawing stage, we can price from the plans and confirm on site later.
Our rooflight costs page explains each cost factor in more depth, and our main skylight installation page for Southampton shows how we fit the unit in step with the rest of your build.
