Living in tornado alley means you need to take precautions to protect your family during severe weather. Building a dedicated tornado shelter in your basement is one of the best ways to stay safe when tornadoes strike. This comprehensive guide will walk you through all the steps for constructing your own below-ground storm shelter.
Overview of Basement Tornado Shelters
A basement tornado shelter is a reinforced, windowless room built with concrete and steel to withstand the damaging winds and debris of a tornado. Shelters are designed to meet standardized criteria for providing near-absolute occupant protection, mainly by anchoring to the basement floor and foundation.
Basement shelters can be custom built rooms, prefabricated storm pods, or even repurposed areas like a bathroom, closet or corner reinforced with storm shelter materials. The essential components are anchoring, thick walls and ceiling, and a heavy duty door.
Benefits of a Basement Storm Shelter
- Maximum safety – Offers near absolute occupant protection compared to above ground shelters by being underground.
- Convenience – Easy access being inside your home so you can reach it quickly.
- Peace of mind – Knowing you have a designated safe space prepares you psychologically and reduces anxiety during tornado watches and warnings.
- Added value – A basement shelter can increase your home’s resale value by as much as 5%; especially attractive to families with children.
- Multi-purpose – The shelter can double as a basement office, workout room, play area, or storage when not used specifically for storms.
Shelter Size Guidelines
Properly sizing your basement tornado shelter ensures there is adequate room for all occupants:
- Minimum floor area of 35 square feet to accommodate two adults.
- Add 15 square feet of extra floor space per additional adult that will occupy the shelter.
- Add 10 square feet of extra floor space per child that will occupy the shelter.
- Ceiling height should be at least 6 feet tall for comfort, but 8 feet allows standing fully upright.
- Include built-in benches along the shelter walls to maximize usable floor space since seats take up less area.
- Oval or round floor plans utilize space most efficiently compared to square or rectangular plans.
Choosing the Best Location
Picking the optimal location in your basement for the storm shelter is very important for safety:
- In the central, interior part of the basement away from all exterior walls is ideal, since this places you furthest away from potential debris impacts.
- Position the shelter opposite any basement windows or glass block walls, as far away as possible so flying glass avoids the shelter entrance.
- Place near load-bearing walls in the foundation and near concrete support columns for greatest structural integrity and anchoring.
- Locate the shelter well away from any hazards like heavy furniture, appliances, or overhead pipes that could damage the shelter or crush occupants during extreme winds.
- Pick a low-traffic area of the basement that won’t disrupt normal household flow or activities when not in storm mode.
Constructing Reinforced Walls and Ceiling
The interior walls and ceiling of a basement storm shelter must be made of reinforced concrete:
- 8-inch thick walls are recommended by FEMA standards for proper strength and impact resistance. Anything less provides inadequate protection.
- The ceiling should be reinforced concrete at least 6 inches thick, securely anchored.
- Walls and ceiling must be firmly anchored into the foundation footing and adjacent walls using bolts and rebar.
- Use #4 rebar grids inside the concrete walls and ceiling to provide critical internal strength. The more rebar, the better.
- Overlap the rebar welded wire meshes for maximum continuity of strength. The rebar should be in a grid pattern, not just vertically.
- Install J-anchor bolts spaced every 2 feet around the perimeter to securely attach walls to the concrete floor slab.
Storm Shelter Doors
Look for pre-hung steel doors tested and rated to meet ICC 500 standards for storm shelters:
- Must have a 90-minute fire rating to withstand residual fires after storms.
- Door must be impact tested to resist 200 mph winds and wind-blown debris.
- Steel door construction should be a minimum of 14 gauge thickness but 12 or 10 gauge is better.
- Look for double doors around 36-inches wide total to accommodate wheelchair access if needed.
- Out-swing style doors are preferred over in-swing for easier and safer exiting after a tornado passes.
- Ensure rubber door seal weatherstripping is included for light, sound, air flow, and water resistance when closed.
Ventilation and Lighting Systems
- Include at least two ventilation pipes running from the shelter ceiling to above ground. This draws in fresh air and reduces humidity.
- Install a natural gas carbon monoxide detector for occupant safety, since gas leaks can occur after tornado damage.
- Add LED battery powered lights attached to the ceiling and along walls to provide emergency lighting during power outages.
- Stock glow sticks, flashlights, and battery or hand-crank lanterns to provide backup lighting sources.
Essential Safety Supplies
Be sure to stock your storm shelter with these supplies:
- Plenty of bottled water and non-perishable foods like protein bars, canned goods, and trail mix. Enough for all occupants for at least 72 hours.
- A well-stocked first aid kit – Include bandages, gauze pads, medical tape, antibiotics, pain relievers, latex gloves, blankets, scissors, etc.
- Blankets and pillows to provide comfort and insulation. Mylar thermal blankets provide best insulation.
- A NOAA weather radio with AM/FM to receive storm warnings and alerts.Include extra batteries.
- An ABC fire extinguisher suitable for all types of fires.
- Shelter occupancy limit signs with maximum safe capacity.
- Games, books, magazines for occupant comfort and distraction during long stays.
The average cost to build a properly equipped basement tornado shelter is $5,000 to $10,000 depending on:
- Overall shelter size and layout
- Type and amount of construction materials
- Local labor and contractor rates
- Whether installing as a DIY project or professionally
Maintenance Tips for Your Shelter
- Test the carbon monoxide detector sensor monthly by pressing the “Test” button.
- Check food supplies, medications, and water yearly to replace anything expired or spoiled.
- Ensure the door fully seals and locks properly when closed. Adjust strike plate or hinges if needed.
- Have an electrician inspect the lighting system periodically to ensure proper working order.
- Refresh emergency supplies like first aid kits, blankets, flashlights and batteries annually.
- Review the tornado safety plan with all household members whenever changes occur.
Before the Storm Hits
When a tornado watch covering your area is issued, prepare by:
- Bringing pets and service animals into the shelter area for safety.
- Charging cell phones and the weather radio fully so they are ready if power goes out.
- Reviewing the emergency tornado plan with all family and household members present.
- Placing routinely needed items like medications, shoes, and eyeglasses into the shelter.
- Monitoring the weather radio, TV, or smartphone alerts closely for local tornado warnings.
Surviving the Storm
Once inside the basement shelter during a tornado warning:
- Remain inside the shelter until the warning expires and storm has fully passed.
- Have shelter occupants kneel down covering their heads and necks with blankets to protect from debris impacts.
- Avoid shelter corners which can attract swirling debris and be vulnerable to collapse.
- Stay away from the main door and all exterior walls for maximum protection.
- Protect airways by sheltering face and head to reduce inhaling dust and dangerous flying debris particles.
- Remain calm, comforting children and others who are anxious or distressed to ease panic.
After the Tornado
When exiting the shelter post-storm:
- Proceed with extreme care and caution as structural damage to the home may have occurred. Watch for debris.
- Wear sturdy shoes and watch each step to avoid injury from broken glass and other sharp debris.
- Beware of exposed nails, screws, and roofing tacks which may have been scattered.
- Check for leaking pipes, live wires, gas leaks and other hazardous utility dangers.
- Contact 911 emergency services immediately if any injuries occurred or dangers are present which require professional assistance.
- Begin clean up and recovery once damage is thoroughly surveyed and conditions are deemed safe.
Having an underground storm shelter provides peace of mind and maximum protection for your family when tornadoes and severe weather hit. Follow this comprehensive guide closely to properly construct your basement shelter meeting or exceeding safety standards. With smart preparation and vigilance, your new safe space will give you and your loved ones the best chance of surviving dangerous storms unharmed. Stay prepared and stay safe!
What size shelter does my family need?
The recommended sizing is 35 square feet of floor space for 2 adults, adding 15 square feet per extra adult and 10 square feet per child. Minimum height should be 6 feet.
What are the strongest materials to build a shelter with?
Reinforced concrete walls and ceiling at least 8 inches thick provide maximum impact resistance and anchoring strength. #4 rebar steel grids inside the concrete also boost structural integrity greatly.
How much does a prefabricated shelter cost compared to building one?
Prefabricated pods made specifically for basements run $3,500 to $5,000 on average. But custom building allows for larger sizes and configuration to your space.