Storm Shelter FAQs
Q: What is an In-residence Shelter?
A: An in-residence shelter is a small windowless room, such as a closet or bathroom, readily accessible from all parts of the house, and designed to provide occupant protection. It can be used for protection in tornadoes or in hurricanes for those OUTSIDE of flood-zone and storm surge areas.
Q: What if I have a basement?
A: There are a variety of basement types: totally below ground, partially below ground, walkout, etc.
- Walkouts typically have doors and windows to the outside and usually are as perilous as residences on grade. However, because they usually have a concrete slab foundation and some earth-protected walls, they provide a good location for construction of an in-residence shelter.
- The above ground portion of partial basements are susceptible to wind forces and flying debris produced by severe wind events. Many concrete masonry basement walls are unreinforced or poorly reinforced and are therefore in jeopardy of collapse from these forces or if the floor diaphragm is removed by the storm. An in-residence shelter located in the partial basement is advised for this type of basement.
- Full basements with concrete roof or first floor slabs offer the best protection of this group. However, the basement walls should be properly reinforced to prevent collapse if the floor diaphragm is shifted by a storm. If the basement roof is not a concrete slab anchored to reinforced walls, the occupants can be vulnerable to falling debris. In this event, an in-residence shelter or a lean-to shelter (modified in-residence shelter) should be provided in the basement.
Q: What if I live in a mobile home?
A: Manufactured homes are generally unsafe in a severe wind event. Because of the threat of injury from flying debris, a safe shelter should be nearby, preferably, to limit exposure to the outdoors. The in-residence shelter can be constructed adjacent to the home, on a permanent concrete foundation, roofed and weatherproofed to provide protection in a 250 mph storm.
Q: My home is built on a pier and beam foundation. How do I provide a shelter in this type of home?
A: A portion of the flooring and floor structure can be removed to expose the soil below which will allow for the installation of the shelter concrete floor foundation. The in-residence shelter can be constructed on this foundation and extend through the raised flooring system. Should this solution not be suitable, a shelter which doubles as a windowless mud room, study, etc. can be built adjacent to the home similar to the one described above for manufactured homes.
Q: What's wrong with my underground shelter? Won't it provide me protection from tornados?
A: Your outside cellar will likely provide safe refuge during a severe wind event. However, research indicates that people are reluctant to interrupt normal living patterns and are prone to wait till the last minute to seek shelter in a cellar remote from the home. This delay subjects you and your family to flying debris while traveling to the cellar. Attempting to reach a remote shelter after a storm is in progress can therefore be extremely dangerous.
When a cellar is all that is available, one should pay close attention to local warning systems, public sirens, TV, radio and weather radios and not delay when a warning is issued.
Q: Can I retrofit my existing home to include an in-residence shelter?
A: Most homes that are built on a concrete slab can be retrofitted. Existing windowless rooms within the home, such as closets, bathrooms and utility rooms are good candidates for remodeling. Normally, the plywood and steel skin shelter is most suitable for retrofits.
Q: Where do I find the doors and hardware for my in-residence shelter?
A: The door can be either field fabricated or store-bought. The fabricated door consists of two layers of 3/4" plywood and one sheet of 11 gauge steel. The manufactured door, a hollow metal door and frame 14, 16, or 20 gauge, can be purchased from your local building supply center. The 14 gauge door will probably have to be special ordered. The 16 and 20 gauge steel doors must be strengthened with a single layer of 14 gauge steel on one side of the door. Solid core wood doors in a hollow metal frame will also work if 11 gauge steel sheet is attached to the door. Commercial doors which were successfully tested by Texas Tech are listed on the "Tested Doors" page.
The plywood door is recommended as a sliding pocket door with a supplemental swinging door for daily use. The sliding hardware is obtainable from most metal building systems retailers. The swing door hardware includes three heavy duty ball bearing hinges and three residential grade mortise deadbolts with a one inch throw. Surface applied slide bolts may be used, but the deadbolts are preferable because they are unlockable from either side.
Q: Can I build a tornado-proof house?
A: You can, but your neighbors probably would not like it in their neighborhood and you would need some of Bill Gates's wealth to pay for it, since I doubt any conventional lender will loan money for it. The reality is that the walls, roof, windows, doors and garage doors must be missile-resistant and the connections of the structural elements must be capable of withstanding 250 mph wind pressures. Missile resistance of walls and even roofs is fairly easy to achieve with current ICF (insulating concrete form) construction; however the connections for long span roofs and tall walls to transfer the loads induced by a 250 mph wind must be 7½ times stronger than those routinely required by today's codes. Then, the issue is how to protect the numerous openings (doors and windows) routinely found in a home. Realistically speaking, it is not practical, much less reasonable, to build a tornado-proof house. Research has shown that what is practical and reasonable is to do a better job of building your home with good wind resistance connections (wind clips, anchor bolts and proper nailing of wall and roof diaphragms) and then include a shelter within the home. Your neighbors, your banker and your "pocket book" will thank you.
To build a wind-resistant house is possible, and even reasonable. Even in a major tornado such as the Oklahoma City tornadoes of 1999, very few areas were actually subject to the highest-level wind speeds (what would be considered F4-F5 winds). So, having a well-constructed house with wind-resistant features will certainly minimize the damage in strong winds and possibly even in all but the central portion of the strongest tornadoes. Many of these features are much easier and less expensive to implement at the time of construction. If you are building a new house, please consider these features. Do not assume your contractor will be familiar with these techniques. To get information on wind-resistant features, see "Protecting your House". Many of the publications listed are available free of charge on-line or as a paper.
Q: How can I purchase an in-residence shelter?
A: There are two options for a shelter: a site-built shelter or a commercially manufactured shelter. A site-built shelter is built into your house; for example, a closet or bathroom of your house is built as a shelter. If you are interested in a site-built shelter, you should obtain a copy of FEMA 320: Taking Shelter from the Storm which includes information and plans for the in-residence shelter. FEMA 320 can be viewed on-line or ordered from FEMA Publications by calling toll-free 888-565-3896. Just give your name and address and a free copy of the booklet will be sent to you.
If you purchase a commercially manufactured shelter, it will either be in one piece or several pieces which fit together. There are above-ground, below-ground and partially below-ground models. For any shelter which is partially or completely above-ground, the walls must be resistant to debris impact. Shelters which have been successfully tested for debris impact resistance by Texas Tech are listed on the “Tested Shelters” page. For below-ground shelters, the door should be resistant to debris impact. For doors which have been tested for debris impact resistance by Texas Tech are listed on the “Tested Doors” page. Please carefully read the first paragraph on each of these pages.
Q: What is a community shelter?
A: A community shelter is defined as a shelter that is designed and constructed to protect a large number of people from a natural hazard event. The number of persons taking refuge in the shelter will typically be more than 12 and could be up to several hundred or more.
Q: Is it possible to obtain plans for a community shelter?
A: There are no plans, but there are design guidelines developed for architects and engineers to follow in designing community shelters. These guidelines are presented in FEMA 361, Design and Construction Guidance for Community Shelters. The guidelines can be downloaded from the FEMA website or ordered by calling 1-800-480-2520 and asking for FEMA 361.
Q: How large should the shelter be?
A: FEMA 361, Section 8-3 provides the following criteria:
- For Tornado Shelters:
- 5 sf per person- adults standing
- 6 sf per person- adults seated
- 5 sf per person- children standing or seated
- 10 sf per person- wheelchair users
- 30 sf per person- bedridden persons
- For Hurricane Shelters:
- 20 sf per person for short-term stay (few days)
- 40 sf per person for long-term stay (days to weeks)
Q: How many doors should the shelter have?
A: Building codes dictate the number and proximity of doors required for spaces of multi-occupancy.
Q: What is the type of door locking device required?
A: Can I use the three deadbolts like for a residential FEMA 320 shelter? No, the three locking deadbolts cannot be used for the community shelter. Building Codes and Fire Codes dictate that spaces of multi-occupancy have “panic type” hardware. Classrooms used as shelters are allowed by most codes to have “classroom function” hardware. In either case, and although the hardware may be locked from the outside, the occupants inside the room can always and freely operate the latch.
Q: What type of door is required for the community shelter?
A: The door, frame and hardware constitute the opening assembly. The door assembly chosen, as required by FEMA, should be an assembly that has been tested for both pressure (1.75 psi) and 3 impacts (15lb. 2x4 traveling at 100 mph). Numerous door assemblies have been tested at Texas Tech and are listed on the Debris Impact Facility website. These tested assemblies include both single and double doors.
Q: Are there special wall and roof materials required for a community shelter?
A: Regarding missile impacts, the same wall and roof designs illustrated in FEMA 320: Taking Shelter from the Storm are applicable for community shelters. However, because community shelters are large spaces with tall walls and long roof spans, wind pressures on these surfaces become a major issue. The architect/engineer should adhere to the guidelines for wind pressure calculations as prescribed by ASCE 7-98, “American Society of Civil Engineers Minimum Design Loads for Buildings and Other Structures.”
Q: Can a community shelter have windows?
A: Impact tests on window glazing have been unsuccessful. Tests have been conducted on tempered, laminated, and bullet resistant glass with unsatisfactory results. In cases where the shelter has to have windows, such as a school classroom, designers have chosen to use tested FEMA 320 door assemblies with three locks as shutters over the windows.
Q: What are some of the other requirements that are unique to community shelters?
A: FEMA 361, Section 8, Human Factors Criteria, addresses this issue. In short, all building codes or ordinances, adopted by local jurisdictions, address issues of health and human safety for assembly occupancies. Some of these issues include requirements for ventilation, sanitation, emergency lighting, food and water.
Q: Can my community shelter be located in the basement of the building?
A: Yes, it can. However, the shelter must meet the Americans with Disabilities Act (ADA). This means wheelchair access by either a complying ramp or elevator with a standby generator.
Q: How many shelters are required for a small community, neighborhood or manufactured home park?
A: When shelters are provided for tornado events, they should be accessible within 5 minutes.
Q: What resources are available for design of school shelters?
FEMA 361: Design and Construction Guidance for Community Shelters is a useful design guide for school shelters. Appendix D includes a case study of a School Shelter Design.
A more extensive case study of Kansas schools has been published by FEMA. Protecting School Children from Tornadoes: State of Kansas School Shelter Initiative is available on the FEMA website.
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National Wind Institute
Address1009 Canton Ave., MS 3155 Lubbock, TX 79409-3155
PhoneNational Wind Institute - 806.742.3476; Renewable Energy - 806.742.6284