Wall-abutting lean-to roof lantern on a rear extension: glass up to the wall

Why a wall-abutting lean-to on a rear extension?

With an ordinary mono-pitch lantern, a strip of roof remains between the glass and the rear wall. A wall-abutting lean-to roof lantern on a rear extension connects directly to that wall instead. You get overhead light and side light down the old wall, exactly where the living room is darkest. From inside, you see one continuous pane starting at the wall.

It does not work everywhere. If the first-floor windows sit low, just above the extension roof, there is too little height for the wall connection. A free-standing mono-pitch roof lantern on the extension is then the better choice. More on rear extensions in general is on roof lanterns for rear extensions.

How much height do you need against the rear wall?

Measure from the finished extension roof to the underside of the window or the sill above. That height has to accommodate the upstand, the glass and the wall abutment profile. The wall-abutting lean-to has a standard pitch of 8°, at which water drains well.

The width usually follows the extension. The further the glass reaches into the extension, the higher it meets the wall. So send a photo of the wall with its windows, and the quote will show what fits.

• Measure up to the underside of the window or sill
• Room for upstand, glass and wall profile
• Standard pitch of 8°
• Width usually follows the extension

How do you make the wall connection watertight?

Leaks on a lantern against a wall occur more often at the wall connection than in the glass. The wall abutment profile goes against the wall, covered by an EPDM lead substitute or a zinc flashing to suit the wall. In brickwork, the connection is usually let into a mortar joint. For an extension with an EPDM roof, the details are in connecting a roof lantern to EPDM.

If you still see moisture inside after fitting, what to do when a roof lantern leaks helps you track down the cause. Sometimes it is condensation or a seam in the roofing, not the lantern itself.

Frame colour, delivery and your quote

Because the wall-abutting lean-to sits directly against the old wall, you see it together with the windows of the house. So choose the colour of the aluminium in relation to those frames. Jet black RAL 9005, anthracite RAL 7016 and traffic white RAL 9016 are popular, and bicolour is possible too. Help with choosing is in choosing a frame colour. The price build-up is on what a wall-abutting lean-to costs.

• Photo of the rear wall with the windows above
• Height from the roof to the underside of the window
• Wall type and colour of the existing frames
• Width and depth of the extension

Frequently asked questions