Wall-abutting lean-to roof lantern on a roof extension: light at height

Where does a wall-abutting lean-to fit on a roof extension?

A roof extension often creates a lower roof section against a higher wall. Think of an extension that does not cover the full width or depth of the house, or one beside a taller neighbouring building. A wall-abutting lean-to roof lantern on a roof extension meets that wall at its high side. Light then falls into the space below, such as a landing, stairwell or bedroom.

If the roof has no higher wall to connect to, a free-standing mono-pitch lantern is simpler. More on the options with roof extensions is on roof lanterns for roof extensions.

What does a roof lantern at height involve?

A lantern on a second or third storey usually goes up by crane or hoist. Plan that with your builder, together with delivery on an agreed date. Every delivery includes safety instructions for lifting and positioning. More in transporting and lifting a roof lantern.

At height, a roof catches more wind. The structural engineer assessing the roof extension includes the lantern when considering wind and snow. Background is in snow and wind loads on a roof lantern. At height too, the standard pitch of 8° ensures good drainage.

• Book the crane lift together with delivery
• Have wind and snow included by the engineer
• Flashing profile to suit the extension's wall
• Thermally broken aluminium frame

Which glass above a bedroom or landing?

Bedrooms often lie beneath a roof extension. Triple glazing is a serious option there: it loses less heat and dampens sound slightly better than HR++. Read more in triple glazing in a roof lantern. If the lantern faces south, solar control glass keeps the upper floor cooler, because heat rises and lingers at the top of the house.

The connection to the wall uses a wall abutment profile with an EPDM lead substitute flashing or a zinc flashing. An extension clad in timber or finished in render gets a different profile from a brick wall. Water runs away from the wall to the outlet of the lower roof section.

Cost and planning with your builder

A roof extension is almost always built by a contractor. They often order directly, with trade prices from the first project and one fixed point of contact; see roof lanterns for contractors. A CAD file is available on request. The lead time from 2 weeks fits most build schedules. What the extension roughly costs is on costs of a roof extension with a roof lantern.

• Drawing or sketch of the extension and lower roof
• Wall type and height of the wall
• Use of the room beneath the lantern
• Preferred delivery date and crane access

Frequently asked questions