The short answer
Yes, when the room needs daylight in the middle of a flat-roofed extension and the roof can take the opening. A lantern gathers light from every side of the sky and gives a low ceiling a sense of height that no flat rooflight can. It is not worth it for a small room, a narrow strip of roof, or a space where you mainly want air and a view of the sky: there, a flat rooflight usually does the job for less work and less disruption.
- Free survey, fixed written quote
- 10-year workmanship guarantee
Where a lantern is worth the extra work
A flat-roofed garage converted into a family room and opened up to the house behind it makes a strong case for a lantern. The old garage door opening becomes a window at the front, and the back of the room, where it joins the hall or the kitchen, sits a long way from it. A lantern over that back half puts daylight where the window cannot reach, and its glazed sides catch low morning and evening sun that would slide straight past a flat pane.
The height helps too. A lantern rises above the roof, so from inside you look up into a glazed space with a ridge at its top. Under a flat roof with a ceiling of ordinary height, that extra volume makes the room feel less boxed in, and it gives a focal point over a sofa or a play area in the middle of the floor.
A lantern also suits a flat roof with enough room around it. It needs a clear area for its kerb and for the roof covering to be dressed up the sides, so a generous roof with a decent fall makes for a straightforward job.
What a lantern will not do
Fresh air is limited. Some models have opening vents, but the opening area is small next to a flat rooflight that lifts on an electric actuator, so for a hot kitchen an opening flat rooflight may help more.
Winter warmth is another gap. A lantern is mostly glass, and even glazing that meets the Part L limit of 2.2 W/m²K loses more heat than an insulated roof. On a cold night you may feel cooler air falling from it, and on a bright south-facing roof in summer it can let in strong heat unless the glass has solar control.
The roof has to suit it as well. A lantern needs joists that can be trimmed around a fairly wide opening, and because it will usually sit over 150 mm proud of the roof, a planning application is normally required unless the council confirms otherwise.
Cleaning is the last point. Leaves and grime gather along the hips and the glazing bars, and on an extension roof that is awkward to reach, cleaning takes some planning. A self-cleaning coating helps, but a lantern under overhanging trees will still need attention now and then.
Myth
A lantern always lets in more light than a flat rooflight of the same size.
Fact
Its upright glass catches light from low angles, but the opening in the ceiling is what lights the room. A flat rooflight over the same opening can light it just as usefully.
When a flat rooflight is the better choice
For a small room, a flat rooflight usually makes more sense. Over a utility room, a cloakroom or a narrow galley kitchen, a lantern's frame and glazing bars take up much of a small opening, and the raised profile can look out of scale from the garden. A frameless unit from our flat roof rooflights range puts more of the opening into clear glass.
It is also the better choice where you want a clean, quiet ceiling, where the extension is overlooked by upstairs windows, or where the work has to stay within permitted development. A flat rooflight on a low kerb sits closer to the roof, so it has a better chance of staying within the 150 mm limit, though kerb and unit together can still exceed it; we measure that at survey.
| Situation | Better fit |
|---|---|
| Deep open-plan room with a dark far end | Roof lantern |
| Small utility, cloakroom or galley | Flat rooflight |
| Kitchen that overheats or needs airing | Opening flat rooflight |
| Room you want to feel taller | Roof lantern |
| Job that must avoid a planning application | Flat rooflight, if it stays within 150 mm and the house allows |
Deciding for your own extension
The quickest way to decide is to stand in the room at the darkest time of day and ask where you would sit if it were brighter. If the answer is a spot well away from the windows in a big room, a lantern is a strong candidate. If it is a small room or you would rather open the roof for air, look at a flat rooflight first.
We look at both at our free survey and give a fixed written quote for whichever fits, with the Building Control notification handled. To see what goes into the price, read what a roof lantern costs; for the full range, go to our roof lanterns section; or book a survey.
