The Building Science Branch of FEMA's Federal Insurance and Mitigation Administration (FIMA) supplies information on designs for safe rooms and building permitting which you will find below.
FEMA does not endorse, approve, certify or recommend any contractors, individuals, firms or products. Contractors, individuals or firms, shall not state they are or produce products that are "FEMA approved" or "FEMA certified."
FEMA has produced specific designs for tornado and hurricane safe rooms that are set forth in FEMA P-320, Taking Shelter From the Storm: Building a Safe Room For Your Home or Small Business. FEMA has also produced design and construction guidance for residential and community safe rooms that is available in FEMA P-361, Design and Construction Guidance for Community Safe Rooms.
In August 2008, the International Code Council (ICC), with the support of the National Storm Shelter Association (NSSA), released a consensus standard on the design and construction of storm shelters. This standard, the ICC/NSSA Standard for the Design and Construction of Storm Shelters (ICC 500), codifies much of the safe room recommendations of the early editions of FEMA P-320 and FEMA P-361. ICC 500 provides the minimum design and construction requirements for extreme wind storm shelters and has been incorporated by referenced standard into the 2009 and later International Building Code (IBC) and International Residential Code (IRC).
Individuals considering purchasing or installing a safe room should contact their local building official about building code requirements but should bear in mind that the extreme loads generated by tornadoes are not covered under model building code requirements. FEMA P-320, FEMA P-361 or ICC 500 can all be used to address these extreme loads.