A shutter in a storm

Storm loading arrives at the guides, not at the curtain. Four things decide whether a door stays in its opening, and one of them is what happens when the power goes.

A shutter on a street elevation takes the storm directly. What fails is rarely the slat: it is the curtain coming out of the guides under pressure, or water driving through a gap the door was never sealed against.

Four things decide the outcome. A curtain and guides specified as one set rather than assembled from two sources, so the slat ends sit in a channel cut for them. Slat gauge and section stiffness, which is what resists the pressure. Guide fixing centres and substrate — the load path out of the door and into the building. And sealing at the bottom rail and the guides, which is what keeps water out once the wind is driving it sideways.

The fourth consideration is power. A storm and a power cut arrive together, so a door that cannot be closed without mains is a door that will be open at exactly the wrong time. That is what the battery back-up and the DC hand lift are for.