FEMA and the National Storm Shelter Association ICC 500 current guidelines for a “group” shelter state that you should allow 5 square feet per person with allowance for at least one 10 square foot for a wheelchair (more if for more than 200 people). When determining what size to build the square footage should also include another 15% beyond the footage for occupancy to allow for supplies – totes or cabinets with first aid, water, flashlights, etc. All of our Group Shelters are built with 8” walls and have full sized handicap accessible 36” doors. The roof is coated with sealer and concrete UV elastic membrane covering which will help keep temperatures cool in the heat of summer. After completion a serial number is affixed to the shelter and a certificate issued stating that all components used by Protection Shelters LLC in construction of Tornado Shelters – doors, vents and louvers — have been tested, inspected and passed by the National Storm Shelter Association and Texas Tech Wind Science & Debris Impact Testing (the company that does testing for FEMA) — and meet the standards for design and construction of FEMA P 361 and NSSA ICC 500 2014 Edition.