How does wind load act on a door?
Wind applies pressure perpendicular to the door surface. That pressure is multiplied by the surface area to become a total load; in other words the load on a door three metres wide is not the same as on one six metres wide. The load shows itself as bending in the panel, the side guide opening up, and strain on the motor.
What do the classes mean?
On industrial doors, resistance to wind load is classified according to EN 12424. The higher the class number, the greater the pressure the door can withstand; class 0 means no resistance has been declared. The manufacturer must document which class the door falls into at which size. The same model can drop to a lower class as the opening grows, which is why the class value must always be read together with the dimension.
- Enclosed yards and sheltered internal facades: a lower class is usually sufficient.
- Open land, industrial estates and the coast: a high class and a reinforced panel are required.
- Corridors between tall buildings: the wind accelerates and can exceed the value declared for the region.
Do not choose a door on wind class alone
- EN 12425: water tightness. It defines whether rain gets in under and beside the door.
- EN 12426: air permeability. In heated areas it affects the energy bill directly.
- EN 12428: thermal transmittance, that is the U value. The choice of insulated panel gains meaning here.
Read together with the wind class, these three values reveal what the door will actually do on the facade. Looking at only one of them gives an incomplete picture.
Measures that work on site
- On wind-exposed facades a second protective door or a windbreak can be planned in front of the high-speed door.
- On high-speed doors, reinforcement bars that increase wind resistance and deeper side guides should be preferred.
- On spiral doors, the ability of the curtain to re-seat itself matters in case it leaves the guide.
- With a wind sensor, the door can be closed automatically above a set wind speed.
What to record during the survey
During the survey the facade orientation, the openness around the building, the prevailing wind direction in the region and the height of the door above ground are recorded. Without this information a wind class may be correct on paper and wrong on site.
On an external facade, choosing a door is not a catalogue exercise but a matter of dimensions and location.
