When two exposure categories could apply, which option best reflects the recommended approach?

When two exposure categories could apply, which option best reflects the recommended approach?

• A. Choose the one that results in lower wind pressure
• B. Choose the category with more obstructions
• C. Choose Exposure C by default
• D. Choose the one that results in higher wind pressure

Answer: (D)

When two exposure categories could apply, use the more conservative exposure because wind design must account for worst-case loads. Exposure categories describe how terrain and obstructions affect wind reaching the structure; the more open or exposed the site, the higher the wind pressures designers must consider. If you have a choice between two categories, the one that yields higher wind pressure is the safer, code-consistent choice, ensuring the roof and its connections are designed for stronger forces. Choosing a category with more obstructions tends to lower the calculated load, which isn’t protective. Defaulting to a less exposed category without justification can under-predict loads. So, applying the higher wind pressure is the appropriate approach.

When two exposure categories could apply, use the more conservative exposure because wind design must account for worst-case loads. Exposure categories describe how terrain and obstructions affect wind reaching the structure; the more open or exposed the site, the higher the wind pressures designers must consider. If you have a choice between two categories, the one that yields higher wind pressure is the safer, code-consistent choice, ensuring the roof and its connections are designed for stronger forces. Choosing a category with more obstructions tends to lower the calculated load, which isn’t protective. Defaulting to a less exposed category without justification can under-predict loads. So, applying the higher wind pressure is the appropriate approach.