Popular Science

Safe room

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It’s the 21st century; you don’t need an undergroun­d bunker for a safe room. In fact, it might even be a worse shelter—because you’re less likely to actually use it. The three safe-room manufactur­ers and installers we spoke to emphasized that the room must be comfortabl­e, accessible, and generally a pleasant place in which to hole up for hours at a time. That is, of course, in addition to being able to withstand the 250-mile-per-hour winds of a category EF-4 tornado.

Walls

The ideal material for the room’s walls is a nearly indestruct­ible insulated concrete form, or ICF. It has a concrete and rebar core, sandwiched between foam insulating layers, with drywall or another finish outside. Not only do the ICFs resist heat in fires and impacts in storms, but they also reduce the sound of those scary noises outside.

Air Supply

The room needs adequate passive ventilatio­n, meaning air can still flow if a power outage takes down the HVAC. Beyond that, the vent system should access the roof of the building. That way, if the house collapses around the room, those sheltering inside can still get that sweet oxygen.

Interior

Make the safe room a familiar, easily accessible space—in a disaster situation, it needs to be comfortabl­e, even for small children. A lot of people use a closet, pantry (hey, the food’s there already), or master bathroom, which provides access to running water as long as it remains safe during the emergency.

Foundation

Anchor the safe room to custom-poured concrete footings or to a home’s existing foundation. With the latter design, hooked J-bolts, which normally tie a house to its foundation, won’t be as strong as robust epoxyancho­red bolts. One 24-square-foot room, held with 19 such bolts, can withstand up to 200,000 pounds of uplift.

Door

As any cop film will remind you, the door is the weakest part of your wall. A safe room’s storm door needs several locks; some use as many as six 1-inch steel bolts to connect the door to the frame. And it should swing inward so you can still get out of the room if debris blocks the entrance.

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