Wind load on flat roofs: who is responsible?

wind load flat roof


The climate is visibly changing. During the summer months, we face both extremely high temperatures and heavy storms that only continue to increase in power and frequency. These storms are known to cause havoc, yet a great deal of the damage they tend to do can be avoided by correctly calculating the wind load on buildings. But who is responsible for determining the wind load on flat roofs?

What is wind load?

The total wind load on flat roofs is the difference, over the entire roof structure, between the underpressure on the top of the roof and overpressure within the building. The underpressure is caused by the suction power of the wind on the outside of the building.

The total wind load depends on three factors:

  • The dynamic wind thrust pressure qp, expressed in Pa
  • The internal pressure coefficient cpi which indicates the overpressure inside the building
  • The external pressure coefficient cpe which stands for the underpressure (suction) on the top of the roof

Why is it important?

Calculating the wind load on a roof, especially for buildings with an irregular shape, is no easy feat. Consequently, calculations are often incorrect or – worse even – not carried out at all. Meanwhile, it is of vital importance that the wind load on roofs be calculated correctly and in great detail to determine the mechanical fixation, the weight of the ballast or the gluing of the roofing materials.

Who is responsible?

The designer is always in charge of wind load calculation. Once finished, they must hand over their findings to the roof sealer by means of a plan divided into different zones. Each zone on the plan indicates the wind forces at play on that particular part of the roof. Basing themselves on this plan, the roof sealer determines how many fixings are needed, what type of glue they can use and how heavy the ballast should be.

SOPREMA calculates wind load for you

SOPREMA does more than provide you with top-notch waterproofing and insulation. You can also turn to us for ROOF CONSULTING. A free service for you to enjoy, it includes the calculation of wind load on flat roofs. Our in-house experts use advanced software and base their calculations on the information you provide.

Keen to learn more about this service? Or do you still have some questions for us concerning wind load on flat roofs? Please don’t hesitate to contact our experts.