In everyday use a skylight and a rooflight are the same thing: a glazed opening that lets daylight through a roof. The words are two names for one idea, and "rooflight" is simply the one that British building rules and roofing trades prefer. Where the two do split is in the regulations, which treat a rooflight and a roof window as different products with different limits.
Why there are two words
"Skylight" is the plainer, everyday word, and in common speech it covers any glazed opening in a roof. "Rooflight" is the term used in British standards, in Building Regulations and by most roofers and glaziers here. A homeowner in Crookes who asks for a skylight and a surveyor who writes up a rooflight are describing the same job.
We use both words on this site for that reason. When you ring or message us, use whichever feels natural. Nobody will correct you, and the quote that follows will say exactly what unit is proposed, by name and size.
Where the trade does draw a line
Inside the trade, the words sort products by how they sit and what they do. The sorting is rough, and firms differ, but this is the common pattern.
| Term | Usually means | Typical roof |
|---|---|---|
| Rooflight | A fixed or opening glazed unit on a kerb, or a lantern | Flat or low pitch |
| Roof window | A window set in the slope, with a hinge or pivot and a flashing kit | Pitched, slate or tile |
| Roof lantern | A raised glazed frame with sloping sides | Flat roof extension |
| Sun tunnel | A small dome feeding a tube to a ceiling diffuser | Pitched or flat |
"Skylight" can mean any row of that table. That is why we ask what the roof is made of and what the room is for before we say which product we would put forward.
The difference that matters: the regulations
Here the two words stop being interchangeable. Approved Document L (Conservation of fuel and power), 2021 edition, volume 1, sets limits for work on existing homes in Table 4.2. For a new or replacement roof window the ceiling is 1.4 W/m²K, with a Band B energy rating as the other way to comply. A rooflight, a roof lantern among them, may go as high as 2.2 W/m²K.
So if someone says "I need a new skylight", the first question is which of the two they have. Replacing a roof window in a pitched slope and replacing a flat rooflight over an extension fall under different numbers, even though both are controlled work. For the process side, see whether a replacement rooflight needs Building Control.
Does the name change planning?
No. Planning and permitted development look at what the unit does to the roof, not what you call it. For a house, the usual test is how far the glass stands above the roof plane and whether any part rises above the highest point of the roof. A low flat rooflight and a roof window set flush to a slope are both likely to sit comfortably inside that test. A lantern stands higher and needs more thought. Flats get no such allowance, and a conservation area, a listed building or an Article 4 direction changes things again. On the Peak side of Sheffield the planning decision may sit with the national park rather than the city. Our planning and Building Regulations guide sets out the conditions in full.
What we ask instead of "which word"
The word you pick tells us little. The roof tells us a great deal. At survey we look at these things:
- Is the roof flat, low-pitched or steeply pitched, and what covers it?
- Is there a kerb already, or will the opening be new?
- Which way does it face, and what is the room for?
- Do you want it to open, and if so by hand, pole or motor?
- What are the rafters or joists doing in the way?
From those answers we choose a product class, and only then a make and size. A new opening means trimming timbers, which is structural work and needs approval, so the survey also tells us how much of the job sits below the glass.
The part nobody names: how it ages
Whatever you call it, a rooflight is made of parts that wear at different speeds. The seals and gaskets age with sun and weather, and the edge seal of the glass unit follows, which shows as mist between the panes. On opening units the motor, rain sensor and controller are next, along with blinds and trims. The flashing or kerb junction around the frame decides whether the roof stays dry around all of it.
That is why every quote we write carries a life plan: the unit, what will wear, and how each part is replaced, including whether that disturbs the roof. Two units that look alike on a drawing can differ a great deal there. One may allow the glass to be lifted out from above. Another may need the whole frame cut free. Read more in how long a rooflight lasts, or see what we check on the day in what happens on a rooflight survey.
Two examples from Sheffield roofs
A 1930s semi in Woodseats has a pitched tiled roof and a loft room that wants more light. The product there is a roof window, and the job is a flashing kit set into the tiles. A Victorian terrace in Walkley with a flat-roofed kitchen at the back wants daylight over the worktop. The product there is a rooflight on a kerb, or a lantern if the room can carry the height.
Ask both owners what they want and each will say "a skylight". The work, the rules and the parts that wear are quite different, which is why we look at the roof before we use either word.
Which word should you use with us?
Either. Ask for a skylight, a rooflight, a roof light or a roof window and we will work out from the roof which one you mean. Our patch is Sheffield plus 30 road miles in every direction, and the survey is free, with a fixed written quote at the end of it. WhatsApp and phone are both fine for a first message, and a photo of the room from below helps.