Roof Lanterns in Essex: What to Check Before You Order
Updated: Sep 2
A roof lantern looks simple once it is finished, but the quality of the result depends heavily on the opening and upstand beneath it. I have seen plenty of problems caused by ordering a lantern before the builder and installer have agreed exactly what size is being measured and where the finished waterproofing will sit.
Measure the correct opening
The lantern supplier may ask for the external upstand size, the roof opening or a finished kerb dimension depending on the system. Those are not interchangeable. The person ordering the lantern needs to know exactly which measurement the manufacturer requires.
I prefer to survey once the opening is formed and check diagonals as well as length and width. A rectangular opening that is out of square can create fitting problems even if the two main dimensions look correct.
The upstand is part of the installation
The height, width and construction of the upstand affect weathering, insulation and the final internal reveal. It also needs to work with the roof covering and waterproofing detail around the lantern.
A lantern should not be treated as an isolated glass product. The roof build-up, falls, outlets and surrounding waterproofing all need to work together.
Think carefully about solar control
Large areas of overhead glass can bring excellent daylight, but they also receive significant solar gain. Solar-control coatings can help make the room more comfortable, particularly on exposed south- and west-facing roofs.
Tint, external appearance, self-cleaning coatings and thermal performance should be considered together. I would rather specify the right glass at the start than try to solve overheating after installation.
Structure and spans
The supporting opening needs to be designed for the loads around it. On new extensions this is normally considered in the structural design, but on alterations to an existing roof I still want to understand what is supporting the kerb and how the opening has been formed.
The lantern frame itself must also be assembled square and supported correctly. Small alignment errors can show up later as drainage, gasket or glass-fitting problems.
Finishing details that separate a good job from a bad one
Clean internal reveals, consistent plaster lines, neat external waterproofing and proper protection of the frame all matter. The lantern should drain correctly and the glass should be seated and sealed exactly as the system requires.
Before handover, I check glass condition, gasket seating, drainage, frame alignment and the surrounding roof detail rather than looking only for obvious leaks.
A final word from an installer
If you already have an opening formed for a lantern, send me photographs with the dimensions and a picture showing the surrounding flat roof. That is usually enough to spot any measurement or upstand issue before an order is placed.
Warning signs and safety advice
Arrange a professional inspection if you notice any of the following:
Overflowing or leaking gutters and visible damp staining.
Loose fascias, soffits, cladding, tiles or roof-edge components.
Sagging, movement or storm damage that could create a falling-object risk.
If any glass, roof panel or external component appears loose or displaced, keep people away from the area beneath it and do not attempt to force it back into position. Seek professional advice promptly.
Eco Windows & Doors Essex provides professional surveys, repairs and replacement installations across Essex. Contact us for clear advice and a practical assessment.
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