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A safe-room tip!


Hi.  James here.  I have a question for you:

I am in the beginning process of building a barn with a small 16 x 12 safe room in the basement.  The walls will be poured concrete, 12” thick and I faced with 9” of stone.  The ceiling is an 8” slab.  I was opening that you could help me with the door and NBC system, as well as suggest what steps need to be taken to ensure I have properly planned for both the installations.  Can you help me with this situation?


Hi James,

Sounds like a neat project!   If you site your safe room in the corner away from the outside wall and next to solid earth (all the way to the top) the walls will likely be OK.  My concern is the thickness of the ceiling.  In Switzerland, bomb shelters are Federal building code…..everybody must have them.  There are one million surplus shelter spaces there, and they are still building 500 shelters each month.   Swiss shelter code is very explicit and well engineered for fallout protection and blast to three atmospheres (45 psi overpressure).  Their ceilings are anywhere from 30 inches to a meter thick, heavily reinforced with lots of rebar.  Depends on what other structure will be built on top, or how much additional earth will be added on top.  Most communal shelters feature a meter of concrete and a meter of earth.  I have lots of video we shot in Switzerland that show this. We also have the Swiss building code on a PDF that you can purchase from TACDA.

Vertical, walk in type doors let in a great deal of radiation.  The Swiss use armored doors, which feature an eight -inch thick concrete door leaf.  This door must be cast into the wall- retrofits are possible, but difficult.

Your emergency escape tunnel hatch should be made of solid steel and sit horizontally on the ground.  DO NOT compromise your ceiling thickness with a hatch… a tunnel out twelve feet or so, and then go vertical for the hatch.

The Swiss concrete shelters with 36 inches of concrete in the ceiling (though good for fallout and blast) WILL NOT defeat initial radiation, which is present within 7500 feet of a nuclear detonation).  At 3 atmospheres (45 psi), initial radiation could be a problem.  But those Swiss shelters that have a meter of concrete over them, plus a meter of earth, will fare well.

An eight-inch concrete ceiling will provide a protection factor (PF) of only around ten.  This will reduce your exposure to outside fallout type (gamma) radiation by only a factor of 11.  My personal minimum is PF-250, which will require a 24 inch ceiling and/or wall between you and the radiation source. If the earth-side wall is completely below grade, then that wall only has to be ten inches thick.   You can play around with the formula by using 2.7 inches of concrete for a halving thickness.  Each 2.7 inches doubles the protection factor.  Ten halving thicknesses provide a PF of 1,000.  That’s 27 inches.  PF1000 makes for a nice shelter that will provide a margin of safety if you get a rainout….that is, all the fallout that was jettisoned into the air by a local ground burst is scavenged from the atmosphere and returned to the ground instead of drifting hundreds of miles downwind. This can raise your exposure level outside the shelter from 1000 rads/hour to as high as 10,000 rads/hour.  A PF250 shelter will probably not be enough in this scenario.

Best regards,

Paul Seyfried

President of Utah Shelter Systems –