Consider the type of glass, framing options, size and specialised features of different rooflights to suit your design.

rooflight open plan - expert advice on rooflight glass specification - home improvements -

Image: De Rosee Sa 

From fixed and opening products suitable for pitched and flat roofs to traditional lanterns, the term rooflight covers an array of overhead solutions. The Grand Designs magazine team spoke to Rebecca Clayton from IQ Glass, who has shared her expert advice on glass specification.

Glazed to perfection

rooflight living room - expert top tips for incorporating rooflights into your design - home improvements -

Image: Velux 

All rooflights to internal spaces should be double glazed as standard, but triple glazing is also available if higher thermal performance is required. A solar control coating will reduce how much solar radiation can come through the unit and reduce overheating that could occur internally.


Self-cleaning coatings can be useful to reduce manual cleaning. These applications are only effective on roof glazing with a pitch of more than 20°. Roof windows with falls lower than this don’t have enough of an angle for dirt to be washed away by rainwater, however, so this type of coating wouldn’t be effective.

Read more: How to choose a roof light for your extension

Toughened glass

grand design rooflight - expert advice on rooflight glass specification - home improvements -

Image: Fraher

Any overhead glazing should have a laminated and toughened inner pane. If the glass is broken, the internal laminate will hold together the inner sheet and stop the glass from falling. Roof glazing should be designed with a maintenance load so you can walk on it if you need to. The company you use will be able to advise you on what glass specification is needed to achieve the loading you want.

If glass is going to be difficult to access and replace, consider heat-soaking to reduce the chance of a spontaneous breakage. 

Internal supports

If the design comprises multiple panes, you may need internal supports. You’ll need internal supports for a structural glass roof if the joints are over 1.3m long. These could be made from steel sections or frameless glass beams. The latter should always be made from low-iron material for maximum clarity. 


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