ASCE 7-22 · TABLE 1.5-1 · RISK CATEGORY IV
Essential Facilities That Must Stay Operational
Risk Category IV covers the buildings a community cannot lose after a disaster — and ASCE 7 designs them off the highest wind-speed map there is.
ASCE 7-22 · TABLE 1.5-1 OCCUPANCY
What Qualifies as an Essential Facility
Structures designated as critical to post-disaster response and community lifelines.
Hospitals & Surgery
Emergency departments, surgery and ICUs treating patients through the event.
RC IVFire & Police
Fire stations, law-enforcement HQ and rescue apparatus bays staying in service.
RC IVEmergency Ops Centers
911 dispatch and EOCs coordinating the entire emergency response.
RC IVDesignated Shelters
Buildings designated as emergency shelters for displaced residents.
RC IVPower & Water Utilities
Power and water facilities required to function during an emergency.
RC IVAviation & Defense
Air-traffic control towers and critical national-defense structures.
RC IVASCE 7-22 · BASIC WIND SPEED MAPS
The Category Ladder — IV Sits at the Top
Each risk category sends you to a different wind-speed map. Higher category, longer return period, higher design speed.
Risk Category I
Low hazard to life — minor agricultural and storage.
300-yr MRIRisk Category II
Standard occupancy — homes, offices, retail, most buildings.
700-yr MRIRisk Category III
Substantial hazard — large assembly, schools, jails, power.
1,700-yr MRIRisk Category IV
Essential facilities — must stay operational after the event.
3,000-yr MRI · HIGHESTPOST-DISASTER OPERABILITY
Why the Strictest Map
Risk Category IV is not about a multiplier — ASCE 7-16 and 7-22 eliminated the wind importance factor entirely. Instead, the risk category selects which basic wind-speed map you read V from.
Essential facilities read off the 3,000-year mean recurrence interval (MRI) map — the longest return period and the highest design speeds in the standard. Actual mph varies by location; the category sets the map, not a fixed factor. The goal is simple: a hospital, EOC or shelter has to remain standing and running while the storm passes and through the recovery that follows.
NEXT STEPS
Classify It, Then Calculate It
Confirm the right risk category, then run the loads with professional ASCE 7 software.