The right pitch for a roof lantern

The pitch of a roof lantern is the angle between the glass and the horizontal. At DagLichtDesign every roof lantern has a standard pitch of 8°, on all four roof types. That angle sits just above the 7° needed for good drainage, lets the rain rinse the glass and keeps the lantern low on the roof. Below you can read what 8° does for water, dirt, daylight and the height of your roof.

Roof lantern pitch and drainage

A roof lantern sits on a flat roof, but the glass itself is never completely level. The water has to go somewhere. The more pitch, the faster rainwater runs to the bottom rail. In practice at least 7° is needed to carry water away quickly and to stop puddles standing on the glass.

At 8° you are just above that. The water runs in one go to the low side and from there to the gutter or downpipe. How the water then leaves the roof is covered in roof lantern and gutter.

The self-cleaning effect of a sloping pane

A pitch does more than drain water. Every shower carries dust, pollen and fine dirt downwards. On a pane at 8° that happens by itself, so the glass stays clear for longer and few dirt lines form along the bottom rail.

No roof lantern is entirely maintenance-free. Leaves and bird droppings sometimes stay put, especially under trees. What you can do yourself to keep the glass and drainage clean is explained in cleaning and maintaining a roof lantern.

A standard 8° on all four roof types

DagLichtDesign makes every roof lantern with the same standard pitch of 8°: the mono-pitch, the wall-abutting lean-to, the gable and the hipped roof lantern. For your builder that keeps things clear. He knows in advance what to set the upstand and the gutter up for.

The only difference per type is where the water goes. On a gable roof lantern it runs to two sides, through a self-cleaning drainage system in the bottom rails. On a hipped roof lantern it runs to four sides and the drainage is hidden in the bars and corner profiles.

• Mono-pitch: 8°, water to the low side
• Wall-abutting lean-to: 8°, the high side meets the wall
• Gable: 8°, water to two sides
• Hipped: 8° all round, water to four sides

Light and height: what 8° does to your roof

A roof lantern at 8° looks almost straight up at the sky. Daylight falls deep into the room from above, even on cloudy days, and from inside you see clouds and blue sky. How much light comes in depends mainly on the glass area, the orientation and the choice of glass. If your roof lantern faces south, look at solar control glass and read what to do about overheating under a roof lantern.

A small angle also keeps the lantern low. The height difference between the low and high side is the depth of the lantern multiplied by the tangent of the angle. At 8° that is about 14 cm per metre of depth, so roughly 28 cm for a lantern 2 metres deep. From the street or the neighbours' garden you will hardly notice it. On a wall-abutting lean-to the junction with the wall stays low as well, see mono-pitch or wall-abutting lean-to.

What the standard pitch of 8° gives you

So you do not need to think about the angle when you send your enquiry. Send the dimensions, a photo and the roof type you want, and the rest is in the quote you receive within 24 hours. How to take the measurements is explained in measuring for a roof lantern.

• Water drains quickly, just above the 7° needed
• Rain rinses most of the dirt off the glass by itself
• Plenty of daylight and a view of the sky
• A low roofline that barely shows from the street

Frequently asked questions