The National Domelight Company has produced a simple 5 step measuring guide to help provide the right measurements and avoid costly mistakes when specifying a rooflight.
It includes a checklist of things to consider and clear diagrams that show exactly what measurements to take when on site.
With so many rooflights and skylights available on the market it can be hard for a merchant or builder to know the right product for the job.
One benefit of using an industry standard splayed upstand is the cost but specifying the correct size is often not straightforward.
Managiing director Scott Couldrey says: “A question that we often get asked is, ‘What roof opening size do I need for a 600 x 600mm rooflight?’ In most cases, the actual dimension that’s being referred to is the clearlight size. In other words, a roof opening size of 600 x 600mm could give them a 400 x 400mm, or 450 x 450mm, clearlight size depending on the specification of the rooflight.”
The measuring guide makes it clear that the critical measurement for replacing an existing rooflight is the overall weathered kerb size not the roof opening size. This is because the thickness of the timber or concrete kerb could be anything from 25mm to 300mm wide and the dome fits over the outside of the kerb.