How long does a roof lantern last?

How long does a roof lantern last, part by part?

How long does a roof lantern last? It depends on the part. A roof lantern consists of an aluminium frame, sealed glazing units, gaskets and sealant joints, and a connection to the roof. Each part ages at its own pace. To estimate the lifespan, you don't look for a single number, but for the weakest link.

Aluminium does not rust the way steel does. A coated profile stays strong and true for decades under normal use; the industry often quotes a lifespan of forty years or more. The choice of aluminium over timber or steel plays a big part here. Timber needs repainting every few years and steel is more prone to rust where the coating is damaged.

• Aluminium frame: usually forty years or longer
• Sealed glazing units: roughly 20 to 30 years
• Gaskets and sealant joints: check and replace in time
• Roof connection: depends on EPDM, bitumen or zinc

When does the glass need replacing?

A sealed glazing unit consists of two or three panes with a closed cavity filled with dry air or an inert gas. An edge seal keeps moisture out. After many years that seal can fail. The first sign is a haze or condensation between the panes that you cannot wipe away. Condensation on the room side is something else; read more about condensation on a roof lantern.

The advantage of an aluminium roof lantern is that the glass is a separate component. If a unit fails, the whole lantern usually does not have to come out. A glazier replaces the glazing unit and the frame stays in place. With polycarbonate it is different. That material can yellow and turn brittle under UV light, so it generally lasts less long than glass.

What decides the lifespan in practice?

Most problems with older roof lanterns are not in the glass or the profile, but in the connection to the roof. A poorly insulated or badly sealed upstand, or roofing that cracks around the lantern, leads to leaks over time. EPDM lasts a long time when properly installed, while bitumen is usually renewed sooner. A well built upstand matters as much as the product itself.

The pitch counts too: standing water holds on to dirt and strains the seals. That is why DagLichtDesign advises at least 7°. Every delivery includes an installation guide with connection details for EPDM, bitumen and zinc.

How to extend the lifespan

Maintenance takes little effort, but it is necessary. Rinse the glass once or twice a year, keep the drainage free of leaves and check that the gaskets are still supple. The article on maintenance and cleaning explains how to do this safely.

• Rinse the glass once or twice a year
• Keep drainage and gutter free of leaves and dirt
• Inspect gaskets and sealant joints every year
• Avoid abrasive cleaners and pressure washers

Frequently asked questions