[Atlas Sneezed]

The wind blowing OVER your roof is putting pressure DOWN on it much in the same way wind flowing over race cars help push them down on the track.

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No. Please don't add ignorance to this thread. Professor Bernoulli reminds us that air in motion has less pressure than stationary air. Any framing carpenter can tell you about the straps they use to hold the roof DOWN when the wind blows hard.

(When you have a house on stilts that lets air pass under it like the space under a car, you can take up the analogy again.)

[jeffers]

"
The wind blowing OVER your roof is putting pressure DOWN on it much in the same way wind flowing
over race cars help push them down on the track.


No. Please don't add ignorance to this thread. Professor Bernoulli reminds us that air in motion has less
pressure than stationary air. Any framing carpenter can tell you about the straps they use to hold the roof
DOWN when the wind blows hard. "

It is more complicated than this. Even greatly simplified, there is a downward component due to the slanted roof, there is a lateral component due to the slanted roof, and there is a lifting component due to the pressure differential.

That said, I framed for more than 20 years, and yes, we use straps to hold the rafters down. Toenails usually don't hold much against any lifting force.

[meyer]

Don't forget that most house roofs are ventilated around the soffit and at the ridge or through designated roof vents. The straps that are used to hold the rafters and/or trusses down are not mandatory in most parts of the country, but are necessary in hurricane-prone areas.

[Normal4me]

We aren't talking about an airplane wing here. Are you saying that a roof would stay on better if the windows and doors were left open during a 150mph wind? I HAVE framed over 150 homes in 18 years and I know what UPLIFT is and the required straps needed to meet codes. There is a reason we don't put four and five foot overhangs on houses anymore and that is because of UPLIFT.