Buildings and wind
Wind loading basics
Wind produces positive pressure on windward walls, suction on leeward walls and roof edges, and uplift on roof surfaces. Gusts, not just sustained speed, drive damage. When an opening breaches, internal pressurization adds upward load on the roof and outward load on walls. The continuous load path-roof covering to deck, deck to truss, truss to wall, wall to foundation-determines whether those loads stay in the structure.
Exposure and terrain
Open terrain, elevated sites, and nearby tall structures increase exposure; dense shielding reduces it. Two houses on the same street can see different loads because of trees, topography, and building height.
Worked example
A garage door fails at 110 mph. Wind enters the garage, pressurizes the attic through gaps, and the roof deck lifts at the eave. The roof covering is not the root cause; the breach and internal pressure are. An inspector should document the garage door’s protection and the roof-to-wall connection, not just replace shingles.
Traps
- Assuming only the windward side matters.
- Confusing sustained wind with gust demand.
- Ignoring internal pressure from a failed door or window.