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FEMA P-320 and ICC 500, explained for OKC homeowners

Installers often say "FEMA" and "ICC 500". Here's what those actually mean, from FEMA's own guidance.

The documents

• ICC 500 is the national standard for designing and building storm shelters; the current edition is 2023. FEMA notes it's referenced by the International Building and Residential Codes.
• FEMA P-320 ("Taking Shelter from the Storm") is FEMA's homeowner guide to residential safe rooms.
• FEMA P-361 holds FEMA's safe room design criteria.

Shelter vs safe room

FEMA P-320 says both must meet ICC 500, but a "safe room" also meets FEMA's stricter funding criteria. The biggest difference: residential safe rooms must meet the highest tornado design wind speed, 250 mph, wherever they are. A residential safe room serves up to 16 people.

The door matters

FEMA's safe room door fact sheet says door assemblies must be tested, listed and labeled by a third party for ICC 500 tornado performance (250 mph). Check the label. FEMA also says it doesn't approve or certify products, so "FEMA approved" or "FEMA certified" claims aren't allowed.

Questions for installers

• Is the unit designed to ICC 500-2023 and FEMA P-361 criteria for 250 mph?
• Can I see the door's third-party certification label?
• How is it anchored, and to what slab?
• Who pulls the OKC permit?

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