Mono-pitch roof lantern on an extension: choosing by room

When does a mono-pitch roof lantern suit an extension?

An extension is usually a separate room with its own purpose: a utility room, study, ground-floor bedroom or treatment room. Such a room often has just one window, or none, because the side wall is close to the boundary. A mono-pitch roof lantern on an extension solves that without opening up any walls. It stands free on the flat roof, on its own upstand.

Does the extension stand directly against a higher wall, your own or the neighbours', and do you want the glass to run right up to it? Then a wall-abutting lean-to on the extension fits better. A general overview is on roof lanterns for extensions.

Which lantern size suits which kind of room?

Think about size from the room's use, not from the roof. A small room quickly becomes bright and warm with a large pane, while a large room with a small pane stays dark in the corners.

The lantern has a standard pitch of 8°, enough for good drainage. That low pitch keeps the upper edge modestly above the roof. This helps if the extension is close to the boundary or overlooked by the neighbours.

• Utility room or WC: 1 metre is often enough
• Study or hobby room: 2 metres
• Bedroom or treatment room: 2 or 3 metres
• Larger or unusual room: a made-to-measure lantern

Connection, drainage and glass on an extension

Older extensions often have bitumen roofing, newer ones mostly EPDM. The installation manual includes connection details for both; for the older type, see connecting a roof lantern to bitumen. Watch the fall: a small extension roof often has just one outlet. Point the low side of the lantern towards it.

Match the glass to the room. Above a bedroom, triple glazing is often the better choice because it loses less heat and dampens rain slightly better; see also a roof lantern above a bedroom. In a south-facing study, solar control glass prevents heat and glare on your screen. For a bathroom or WC, choose obscured glass so nobody can look in from above.

Delivery, fitting and your quote request

After collection or delivery, your builder fits the lantern. The extension itself sometimes needs permission, the lantern usually does not; see permission for a roof lantern. An indication of the total is on costs of a roof lantern on an extension.

• What the extension is for and how you use it
• External roof dimensions and the preferred position
• Distance to the boundary and neighbours' windows
• Photo of the roofing and the outlet

Frequently asked questions