Roof Calculator
Work out your GRP flat roof coverage
Enter your roof's dimensions, deck type and upstand details below for an instant area estimate, kit recommendation and materials list.
Common questions
What's an upstand and why does it need extra material?
An upstand (or kerb) is the vertical edge where the roof meets a wall or parapet. It needs the same laminate wrapped up the vertical face, so it adds area on top of the flat roof itself.
Do I need a trafficable finish?
If the roof will be walked on regularly (e.g. a roof terrace or access route), choose trafficable — this adds an extra reinforcement layer and recommends an anti-slip topcoat.
What if my roof isn't a simple rectangle?
Break it down into rectangular sections and run the calculator for each, or send us your dimensions via the contact page for a quick check.