Seismic and wind hardware

Metal straps, holdowns, and twist straps designed to help the house resist seismic and wind forces. There’s a ton of hardware in this thing: one framer told me I have as much metal as a typical new 6,000-square foot Anchorage home.

A primary purpose of this hardware is to keep the house stable during a seismic event. Wood-framed residential structures are surprisingly good at keeping occupants alive during earthquakes because they’re resilient and light. However, because flexing dissipates energy into joints and finishes, wood-framed houses often sustain serious structural and aesthetic damage during quakes. One publication compares this to a car crumpling during a crash–saving the occupants but totaling the car.

Research by HUD, FEMA and others has shown that residential structures in high seismic risk areas should be both stiff and strong. Stiffness minimizes deflection between the top and bottom stories of a home caused by ground shaking. Strength keeps structural members and joints from breaking or coming apart. All of the hardware here is basically designed to do one thing: lock the house together from the roof the foundation, allowing the whole structure to move as a strong, unified mass during a serious wind or seismic event.

Wind and earthquakes create similar lateral forces, but wind also causes problems with uplift on the underside of overhanging roofs. In a worst-case scenario, wind uplift can rip a roof entirely off of a structure. Tying the house together with metal hardware essentially anchors the roof to the ground.

Photos taken February 1, 2020. Posted February 23, 2020.