Extension with a roof lantern: more daylight deep into the house

An extension with a roof lantern solves a familiar problem: the extension makes the house deeper and the middle of the room darker. A roof lantern in the flat roof brings the daylight back, exactly where the old rear wall used to be. Position, size, type of glass and a sound connection to the roof covering all matter. The structure around the opening and the insulation also need attention. That way you keep the light, without heat in summer or cold in winter.

Why do people choose an extension with a roof lantern?

An extension a few metres deep makes the living room or kitchen bigger, but light from the rear facade reaches the middle of the house less well. A roof lantern provides daylight from above, which falls deeper into the room than light through a facade.

We often combine a roof lantern with a sliding door. The glazed door gives a view of the garden, the roof lantern brings light into the middle. Read more about that combination in fitting a sliding door and on our extension service page.

Where do you place the roof lantern in the extension?

The best place is usually directly along the old rear wall. In an extended house that is where it is darkest, and the light also falls on the wall, which makes the room feel larger. In an extension for a kitchen diner the roof lantern can also go above the kitchen island or the dining table.

• Along the old rear wall, where it is darkest
• Above the dining table or the kitchen island
• Well away from the roof edge, for the roof covering
• Facing south, preferably with solar control glass or a blind

Which glass and which shape do you choose?

Roof lanterns come flat, as a lean-to with one sloping pane or as a ridged lantern with two slopes. A slight pitch helps drain rainwater and dirt. HR++ double glazing is standard, triple glazing insulates better and keeps the glass surface warmer in winter.

Facing south, it can get warm under a roof lantern in summer. Solar control glass or a blind helps. Also ask about laminated glass on the inside, for safety above your head.

What does a roof lantern mean for the roof and structure?

An opening is made in the joists of the flat roof. Around it the joists are reinforced with trimmers. An upstand goes on the opening, and the roof lantern rests on it. The upstand is insulated and the roof covering is neatly worked up against it.

That junction is where things often go wrong if the work is not done carefully. A well detailed flat roof with an upstand stays dry for years. Insulating the roof and upstand is part of it too, see insulating an extension.

What does an extension with a roof lantern cost?

A roof lantern comes on top of the cost of the extension itself. The price depends on the size, the shape, the glass and any shading. The upstand, the trimming and the work on the roof covering also count.

For the rough costs of the extension, see extension costs per m2. In a tailored quotation we list the roof lantern as a separate item, so you can make a deliberate choice.

Frequently asked questions