Frequently Asked Questions About Building Science

Use the filters below to find answers to frequently asked questions about Building Science guidance regarding:

  • General Building Science questions
  • Substantial Damage Estimator (SDE) tool
  • Safe rooms
  • Floods
  • High winds
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Please visit the Building Science Resource Library to reference all hazard-specific publications and guidance documents.

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What Is the Cost of Installing a Safe Room in a New Home?

During the construction of a new home, the estimated basic cost to construct a safe room using the design plans in this publication ranges from approximately $9,400 to $13,100 for an 8-foot × 8-foot safe room and from $18,900 to $25,500 for a 14-foot × 14-foot safe room. The basic cost includes materials, labor and contingency but does not include the cost and installation of the safe room door assembly, which is addressed in the following section. Further, safe rooms installed in existing homes will be more expensive than those built as part of new construction. The cost of your safe room will vary depending on a variety of factors, including:

  • Safe room construction materials (CMU, concrete, wood, insulated concrete form [ICF])
  • Type of foundation on which the house is built (refer to Section 3.7)
  • Depth of footing; cost estimates are based on a minimum depth of 2 feet, 6 inches
  • Your location within the United States (because of regional variations in labor and material costs)
  • Whether you are building a safe room in a new home or retrofitting an existing home
  • Any added amenities (e.g., bathroom fixtures)

Prospective safe room owners are often surprised at the high cost of safe room door assemblies. Market research shows that entry level prices for properly tested and labeled residential safe room door assemblies are between approximately $2,500 and $3,200 (in 2021).

Residential prefabricated safe room costs, for just the units themselves and excluding site preparation and other costs, are approximately $5,000 to $6,000.

Section 4.3 of FEMA P-320 provides the assumptions and details of the cost estimates provided above.

What Is the Minimum Square Footage per Person for a Residential Tornado and Hurricane Safe Room?

For residential safe rooms, the usable tornado safe room floor area should include the protected occupant area between the safe room walls at the level of fixed seating, where fixed seating exists, minus the area of sanitary facilities or other items that impede usage of the safe room area. Table 3 shows the minimum safe room floor area per occupant for residential tornado and hurricane safe rooms.

Weather EventResidential Safe Room TypesMinimum Usable Floor Area per Safe Room Occupant
TornadoOne- and Two-Family Dwellings3 square feet
 Other Residential5 square feet
HurricaneOne- and Two-Family Dwellings7 square feet
 Other Residential10 square feet
Table 3. Occupant Density for Residential Tornado and Hurricane Safe Rooms

*See FEMA P-361 for more information on usable safe room floor area.

What Is the Minimum Square Footage per Person for a Hurricane Community Safe Room?

For a hurricane community safe room, the number of spaces for standing or seated, wheelchair-bound, or bedridden people should be determined based on the expected occupancy of the safe room as calculated by the designer and the applicable authority having jurisdiction. As a minimum, each community safe room should be sized to accommodate at least one wheelchair space for every 200 occupants.

It is also important to note that community safe rooms should provide equal access for all persons in accordance with all federal, state, and local Americans with Disabilities Act (ADA) requirements and ordinances. Table 2 shows the minimum safe room floor area per occupant for hurricane community safe rooms. The minimum usable floor area per safe room occupant is larger for a hurricane community safe room than for a tornado community safe room because occupants require a longer sheltering time for hurricanes.

Hurricane Community Safe Room OccupantMinimum Usable Floor Area* per Safe Room Occupant
Standing or Seated20 square feet
Using a Wheelchair20 square feet
Relocated to a Bed or a Stretcher40 square feet
Table 2. Occupant Density for Hurricane Community Safe Rooms

*See FEMA P-361 for more information on usable safe room floor area.

What Is the Minimum Square Footage per Person for a Tornado Community Safe Room?

 For a tornado community safe room, the number of spaces for standing or seated, wheelchair-bound, or bedridden people should be determined based on the expected occupancy of the safe room as calculated by the designer and the applicable authority having jurisdiction. As a minimum, each community safe room should be sized to accommodate at least one wheelchair space for every 200 occupants.

It is also important to note that community safe rooms should provide equal access for all persons in accordance with all federal, state, and local Americans with Disabilities Act (ADA) requirements and ordinances. Table 1 shows the minimum safe room floor area per occupant for tornado community safe rooms.

Tornado Community Safe Room OccupantMinimum Usable Floor Area* per Safe Room Occupant
Standing or Seated5 square feet
Using a Wheelchair10 square feet
Relocated to a Bed or a Stretcher30 square feet
Table 1. Occupant Density for Tornado Community Safe Rooms

*See FEMA P-361 for more information on usable safe room floor area.

Can a Safe Room Installation Contractor or Product Supplier Be Certified by FEMA?

No. FEMA does not endorse, approve, certify or recommend any contractors, individuals, firms or products. Contractors, individuals, or firms shall not claim they or their products are "FEMA approved" or "FEMA certified." Any claims of compliance with FEMA P-361 and ICC 500 criteria should be verified through independent testing or engineering analysis. Producers, contractors, or firms that wish to indicate that their safe room products have been properly designed and tested should notify consumers whether the products meet or exceed the safe room criteria found in FEMA P-361 and provide supporting documentation such as test certification documents.

Some states maintain their own certification programs. Please contact your state Emergency Management Agency for information on becoming certified by your state to build safe rooms. View contact information for state offices and agencies of emergency management. There is no federal certification.

Does FEMA Verify Or Certify Design Calculations Published By Manufacturers For Their Products?

No. FEMA does not verify or certify design calculations for any product. The registered design professional who signs the certification attests that the product in question meets the requirements specified on the certification. The design professional should be licensed in the state in which the product will be used. All products must be properly installed for their intended use(s) only.

Does FEMA Approve, Endorse, Or Certify Any Products?

Due to federal regulations, FEMA does not endorse, approve, certify, or recommend any contractors, individuals, firms, or products. Contractors, individuals, or firms shall not claim they or their products are “FEMA approved” or “FEMA certified.” You should work with a registered design professional, such as an architect or engineer, who is familiar with safe rooms to verify that your safe room meets or exceeds current FEMA criteria.

Where Can I Find Information About Obtaining FEMA Funding To Construct A Safe Room? Are There Any Funds Available In My Area?

For project eligibility and financial assistance questions, please contact your State Hazard Mitigation Officer (SHMO). Your SHMO can tell you what information must be provided for your project to be considered for funding, as well as any applicable federal, state, and local design requirements. Your SHMO can also provide you with information on funding sources.

Do Any Local Jurisdictions Require Safe Rooms?

Local jurisdictions generally do not require residential safe rooms or storm shelters. However, some communities have offered incentives (such as reduced property taxes) for owners who wish to build a safe room or storm shelter for their home. Some state and local governments have engaged in grant programs with the federal government to partially subsidize the construction of both residential and community safe rooms.

The 2015, 2018, and 2021 International Building Code® (IBC®) require the construction of community storm shelters to be included when K-12 schools and first responder facilities are constructed in areas where the storm shelter design wind speed for tornadoes is 250 mph. These storm shelters must comply with the adopted code’s referenced edition of the International Code Council’s (ICC) Standard for the Design and Construction of Storm Shelters, also known as the ICC 500.

ICC 500 provides the minimum design and construction requirements for extreme-wind storm shelters and has been incorporated by reference as a standard to be followed for storm shelter design and construction in the 2009, 2012, 2015, 2018, and 2021 International Building Code (IBC) and International Residential Code (IRC), as well as the 2018 and 2021 International Existing Building Code (IEBC). Those involved in the design, construction, and maintenance of safe rooms should become knowledgeable about both FEMA guidance and ICC code and standard requirements that pertain to sheltering from extreme winds. Knowledge of the information in these publications will help those involved navigate local applicable codes, employ best practices to provide near-absolute protection, and apply for FEMA funds that may be available (if desired).

My House Has a Basement. Do I Need a Safe Room?

Some strong tornadoes have resulted in loss of floor framing, collapse of basement walls potentially leading to death and injuries to individuals taking refuge in a basement. The acceptable level of protection is an individual decision. A basement may be the safest place to seek shelter in a home without a safe room, but the basement will not provide the same level of protection as a safe room unless it has been designed and constructed in accordance with the criteria in FEMA P-361.

A basement is a good location to install or build a safe room, but access for handicapped or physically challenged individuals may be limited. The flood risk of your location may also help determine whether your basement is an appropriate place for a safe room. If your house or neighborhood is prone to flooding, the basement may not be suitable for taking refuge.

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