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Showing water where to go on a flat roof

Although flat roofs sealed with waterproofing solutions are able to hold standing water, this is not a standard practice. It can lead to problems such as additional load to the structure, growth of algae, etc.


Different countries around the world have different local requirements to provide flat roofs with a minimum slope to drain out the water. Among the most common practices to create a slope on flat roofs are to create a slope on the roof structure itself, or to add screed laid to falls on the flat roof. Creating a slope on the structure requires proper designing of the building in an early phase and can incur in higher construction costs. Using screed to create a slope takes longer, as the screed - usually made of concrete - needs to dry out, and can add significant dead load on the structure.


However, there is also a third option to create a slope on flat roofs: the use of tapered insulation – rigid insulation boards that have a slope - installed in such a way so that they help direct the water towards the drain location.


Tapered insulation is much lighter than the other conventional methods and does not need to dry out. This not only saves time but is also a more economical and effective alternative method to create slope in a flat roof for drainage purposes.



Tapered insulation boards are available as part of our RESISTA PIR insulation product range. They are lightweight insulation boards with a density of about 32 kg/m3, adding minimum weight to the structure and providing excellent thermal performance.


RESISTA tapered boards are available in combinations of different thicknesses to create a continuous slope and ensure the correct drainage of water, eliminating the risk of ponding water on the roof. In order to offer solutions for every roof configuration, the range is completed by pre-cut ‘valley and ridge’ boards which make installation easier and effective.


Elevate’s support goes beyond the product. Our roofing specialists can provide assistance in the design and layout of the tapered roof, proposing the optimal solution for each project.