I've been through three myself. Had coworkers lose their house in this one almost 8 years ago.
A timeline and recap of the Washington Tornado, which occurred eight years ago today on 11/17/2013.
www.hoiabc.com
This was another eerie mid-November tornado that you just don't expect.
One of the worst things you can do is be on the road if it hits. I've been in a small midwest town with tornado sirens going off and at work. My boss would get us all down to the basement instead of letting us drive home.
Building wise, I don't know much about where they worked. There's not much out there that can withstand an F5. Hurricanes are one thing. F5's are an entirely different beast. They can be twice as powerful as the most powerful hurricane. And the twisting motion is just something you have the see the aftermath of to understand the destructive nature.