FEMA P-361, P-320 and ICC 500 explained

Last updated: October 10, 2026

ICC 500 is the building standard for storm shelters — the one codes reference. FEMA P-361 is FEMA's guidance and criteria for residential and community safe rooms, which goes beyond ICC 500 in places and is what FEMA-funded safe rooms must meet. FEMA P-320 is FEMA's homeowner and small-business version, with prescriptive plans. A shelter you buy should be documented as meeting FEMA P-361 criteria and ICC 500, with test reports and labels to prove it. And no shelter is "FEMA approved": FEMA states that it "does not endorse, approve, certify, or recommend any contractors, individuals, firms, or products."

The three documents

FEMA's safe room page says safe rooms must follow the guidance in P-320 and P-361. FEMA requires prefabricated residential safe rooms funded through its grants to show compliance with ICC 500.

What the standards protect against

• Wind. FEMA's criteria design tornado safe rooms for a 250 mph tornado wind speed.
• Debris. Walls, roofs and doors are tested against wind-borne debris — "missiles" a tornado can propel — at the speeds the standards specify.
• Uplift and overturning. The anchorage and foundation are part of the design; a steel room is only as good as what holds it down.
• Occupancy. Floor area per person, ventilation, and access.

"FEMA approved" isn't a thing

FEMA doesn't test, approve or certify shelters or companies. A seller who says "FEMA approved" or "FEMA certified" is misusing the name. What a seller can truthfully claim is that a product was designed and tested to meet FEMA P-361 criteria and ICC 500, with documentation.

Who tests shelters now

For years, Texas Tech University's National Wind Institute was the best-known debris-impact testing lab. It now says it "is no longer offering debris impact testing services for standards compliance" and directs compliance inquiries to labs and evaluators including Intertek, UL and ICC Evaluation Service. A test report from any accredited lab should name the standard, the edition, the product tested and the results.

The NSSA seal

The National Storm Shelter Association is a trade association of shelter producers that co-developed ICC 500 with the ICC. It runs a seal program and web listing for member producers. The seal is a useful signal; ask what it represents for the specific product and still ask for the test reports.

Doors: the part that fails first

The door is the most vulnerable part of a shelter, so it's tested as an assembly — door, frame and hardware. FEMA's fact sheet on residential tornado safe room doors says they "must be rigorously designed, constructed, tested, listed, and labeled," with compliance shown "via labels that are attached to approved doors." No label, no proof. See doors, anchors and maintenance.

The paperwork to ask for

Before you buy, ask the seller for:

1. The test report for the shelter model — lab name, standard and edition, what was tested, results.
2. The door label and the door's test listing.
3. The anchoring specification — slab thickness and strength, anchor type, spacing, edge distances.
4. The installation instructions the installer will follow.
5. Occupancy rating — how many people at what floor area.
6. Ventilation details.
7. Warranty terms — who services it, where.

Keep all of it with your house records.

Residential codes and ICC 500

Model residential codes reference ICC 500 for storm shelters; building one is a choice, not a code requirement for a home. Local permitting decides how it's reviewed — unincorporated St. Charles County, for example, requires a permit for every storm shelter. See permits.

Related guides

• Safe room doors, anchors and maintenance
• Compare storm shelter quotes
• The complete St. Louis storm shelter guide

Frequently asked questions

What's the difference between FEMA P-361 and ICC 500? ICC 500 is the consensus construction standard that codes reference. FEMA P-361 is FEMA's guidance and funding criteria, which builds on ICC 500 and is required for FEMA-funded safe rooms.

Is NSSA certification the same as FEMA approval? No. FEMA doesn't approve products. NSSA is a trade association with a seal program; ask for test reports either way.

What's a "storm shelter" versus a "safe room"? ICC 500 uses "storm shelter"; FEMA uses "safe room" for shelters meeting its criteria. In everyday use they overlap.

Does a shelter need to be tested if it's built in place? A reinforced room built to FEMA's prescriptive plans or an engineer's design isn't lab-tested as a product, but its door assembly must be.

Get a quote

We hand over the manufacturer's documentation with every unit. See above-ground safe rooms, or get a quote.