USDA Forest Service researchers have developed a tornado shelter made of wood that provides powerful protection at an affordable cost.
With safety and security in mind, Forest Products Laboratory (FPL) engineers designed the residential tornado shelter to resist the high wind pressure and debris impacts generated by high-wind events.
Most importantly, the wood shelters can be built into an existing home using readily available materials and tools.
“The 2019 tornado season has already been a deadly one, highlighting the concerns of millions of Americans about staying safe through these terrifying storms,” said Forest Service Deputy Chief of Research and Development Alexander Friend. “We have designed an affordable shelter that can be built by a local contractor or an advanced do-it-yourselfer using readily available materials. We also wanted to make sure this shelter would be easy to retrofit into existing homes. ”
The agency’s scientists achieved this by using easy-to-obtain materials and minimizing the need for specialty materials and hardware.
The 8-by-8-foot room can be built by a local contractor or handy homeowner, which can result in substantial cost savings. The estimated cost of materials for the shelter is between $3,000 and $4,000, but costs can vary in different local markets.
The shelter walls are constructed using three layers of 2-by-8-inch lumber nailed and glued together and stacked log-cabin style, then sheathed with three-quarter-inch plywood. A specifically designed roof and door, ventilation holes, and anchors into a concrete slab complete the shelter. The structure’s size makes the space suitable for other uses, such as a bathroom or utility room, when not needed in an emergency.
Tornado shelters made of steel and concrete are available on the market, but these can be costly and often need to be built during the original construction of the home. Building with wood lowers costs and makes it easier to integrate shelters into existing homes as well.
The shelter recently passed industry safety standards, meeting the impact and wind requirements of the “Standard for the Design and Construction of Storm Shelters” as defined by the International Code Council/National Storm Shelter Association.
Testing to meet this standard required FPL researchers to use an unusual tool: an air cannon. The cannon used compressed air to shoot a two-by-four foot lumber stud weighing 15 pounds at 100 mph at the storm shelter. In a successful impact test, the “missile” will not penetrate the room, will not create significant debris, and will not cause permanent wall deflection of more than three inches.