Standards & Codes
ICC 500
Also known as: ICC 500-2023, ICC/NSSA 500, storm shelter standard
Why ICC 500 matters
ICC 500 is the document that turns marketing claims into measurable tests. A shelter advertised as 'F5 rated' or 'tornado proof' without an ICC 500 test report is essentially unsupported. The test report is what proves the unit performs.
Tornado vs hurricane shelters in ICC 500
ICC 500 has different design events for tornado and hurricane shelters. Tornado shelters use the 250 mph wind and a 15 lb 2x4 missile. Hurricane shelters use a regional wind speed map and a 9 lb 2x4 missile. Both events stress the door and envelope, but tornado design is the controlling case in Tornado Alley and Dixie Alley.
Latest revision
The current edition is ICC 500-2023. Earlier editions (2008, 2014, 2020) are still seen in older test reports. For a new install, confirm the test report references at least the 2014 edition, and ideally 2020 or 2023.
Distinguished from
- FEMA P-320
- P-320 is a federal guideline aimed at homeowners and builders. ICC 500 is the underlying technical standard with the actual test procedures.
- NSSA listing
- An NSSA producer listing means the company submits to third-party verification that their units match the tested design. The test itself is governed by ICC 500.
Practical example
Two prefab above-ground shelters look identical. One has an ICC 500-2014 test report on file for the exact wall and door combination shipped to your site. The other has 'designed to ICC 500' on a brochure. The first is buyable. The second is a question mark.
Authority: ICC 500-2023. Last reviewed 2026-06-04.
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