How to Design a Nuclear Fallout Shelter

Nuclear fallout shelters have been stigmatized as the ultimate prep for the paranoid and the butt of many jokes. But now that we’ve all been reminded that nuclear accidents can happen, nobody is laughing anymore. My hope is that nuclear preparedness becomes a topic we’re more comfortable talking about again. I’d hate to see us succumb to fear mongering and instead educate ourselves, prepare for the possibility, and work toward eliminating nuclear power and weapons.

The Cold War seemed to create a general misconception – that a nuclear incidents are not survivable. So most folks just gave up on the topic assuming there was nothing we could do. Even well-intentioned documentaries like Countdown to Zero tend to leave the viewer with a total sense of dread and hopelessness. The truth is that reactor accidents and blasts are survivable because radioactivity diminishes faster then we might think. After the initial incident those that stayed sheltered would be left to rebuild, just like those who survived the bombings of Hiroshima and Nagasaki. Life would eventually return to a level of normalcy.

A misunderstanding of half-life might also be contributing to the general confusion about radiation. Reactor waste (like fuel rods) takes thousands of years to decay; but fallout from a nuclear blast can return to safe levels (for evacuation) in as little as three to five weeks. This mix up, and Hollywood, are probably the culprits for the spreading of the idea that nuclear fallout will destroy life for thousands of years – which is nonsense.

This doesn’t mean we should allow the continued proliferation of nuclear reactors and weapons unless we want to eventually move underground, but while we are busy demanding the end of nukes, we should also be educating ourselves about the necessary tools and techniques for surviving nuclear accidents and blasts.

I’m not an expert fallout shelter designer, but the basics are easy to understand. So now that we’ve all been reminded that radiation from nuclear fallout is all bad, lets move onto fallout shelters.

Fallout Shelter Basics

The basic design principals are simple. The more mass and/or distance you put between you and radiation the better. A useful analogy for understanding the nature of radiation is to think of it as heat you can’t see, feel, hear, taste, or smell. The farther you are away from any heat source, and the more stuff between you and the heat source, the less likely you are to be burned.

It’s also important to understand that the amount of time you’re exposed to radiation the more of an adverse affect it will have on your body. So while the amount of radiation currently coming across the Pacific is insignificant, over time it could be a bigger problem if the source is not contained.

Since we can’t detect nuclear radiation without special instruments we’re vulnerable. For civil defense purposes there are two primary types of meters, survey meters and dosimeters. A survey meter (like a Geiger counter) detects the amount of radiation currently present. A dosimeter tells you how much exposure you’ve had over time. Both are useful because the survey meter can alert you to the source and intensity of a danger while a dosimeter can tell you how much total radiation you’ve received.

Unfortunately very few people have access survey meters or dosimeters. To make matters worse store shelves are currently bare as a result of the nuclear accident in Japan. As soon as supplies become available it might be a worthwhile investment and there are some low-cost options like the NukAlert and the RADSticker. But I also suspect a whole new generation of civil defense meters will flood the market as companies work to meet the renewed demand.

This illustration, found in a recently published guide from The U.S. Department of Homeland Security, shows the safest places to take shelter in buildings. As you can see the deeper you are inside a building, surrounded by the mass of the building and/or ground outside, the safer you’ll be. This is a good tactical strategy to know in an emergency but also a good visual teaching tool for understanding what is needed to shield yourself from radiation.

As you can see from the illustration above, typical homes provide little protection against radiation. This is simply because most of our homes are built from relatively lightweight materials. Below is an illustration I whipped up based on shielding design information available on Wikipedia.

Some materials shield against radiation better than others. Each of the wall thicknesses below shield the same amount of radiation. Lead provides the thinnest wall while packed soil provides the most cost effective wall, albeit at 3-feet thick compared to 4 inches of lead. For more information see this wikipedia article on radiation protection.

The drawing below shows three ways to build a house, kind of like the the story of The Three Little Pigs.

  • The first house (left) is what most of us in America occupy, lightweight stick-framed structures framed with 2x4s. The walls are thin and have virtually no mass.
  • The second house (center) represents an earthen home, like an adobe or earthbag home with a conventional roof. The thick walls would provide a lot more shielding than the stick-framed home, but the roof would still allow radiation from any airborne fallout to penetrate the home from above.
  • The third house (right) has 2-foot thick concrete walls and dome masonry roof. This house would provide the most protection and is the recommended minimum thickness for an above ground concrete fallout shelter.

In an article titled, U.S. Rethinks Strategy for the Unthinkable (December 2010), The New York Times reveals that the U.S. Government is now recommending that people should stay inside until we’re told it’s safe to go out – instead of making a run for it – even if you’re home is a flimsy box.

While this seems crazy at first it actually makes sense because the number one thing that will hurt you in a nuclear disaster (after blast effects) is inhaling or ingesting radioactive material. If you get radioactive material on your body you should wash it off gently. If radioactive material gets into your bloodstream through a cut, eyes, mouth, etc, it can’t be washed off. So you’re best odds are to stay inside/under the safest building around – and to stay inside until the radioactive material has decayed to safe levels.

So just to recap, the basic shelter requirements are:

  • Ample mass to block the radiation
  • Air filtration to prevent inhaling or ingesting radioactive material
  • Water and food for several weeks
  • Radiation meters
  • Energy sources both electric and burnable fuel
  • Radio for communications
  • Simple waste disposal
  • A way to wash off radioactive material
  • Security measures
  • Since radiation can’t make turns, use 90-degree turns at doorways and air ducts

Fallout Shelter Design Study

Below is an illustration of a shelter I whipped up using information from the available sources as guides. To build an underground shelter like this would require some careful engineering and construction expertise – so please do not attempt to build a shelter solely from what you read here. Do your homework and due dilligence before embarking on any project with a multi-ton roof. A roof cave-in will hurt you faster than radiation.

It’s one room with two entrances. The room is 6′ 8″ wide and 12′ 8″ long, which also ironically happens to be about the size of many trailer-based tiny houses.

The design is intended for a family of four. At one end is a set of fold-down bunks that could double as seating space when the family is not in bed. Below the bottom bunks would be space for food and water storage in 5-gallon buckets.

Dividing the bunks from the main living space are two tall cabinets (or lockers) for the occupants’ possessions, which would be mostly clothing, books, and personal items. These items, as well as the food and water, would need to be stocked and stored prior to a disaster so that the family could escape to the shelter as soon as a threat was detected.

The main living space would also contain additional water storage (110 gallons in two stacked 55 gallon drums) a small food preparation space, four folding chairs, and a fold-out table.

The toilet (bucket-style sawdust toilet) would be located in the main entryway just outside the interior shelter door on the bunk-side of the shelter. The toilet end of the entryway would be as well shielded from radiation as the main shelter but would provide a little more privacy from the main shelter. The potential oder from the simple emergency toilet would also carried outside by cross ventilation.

Air itself doesn’t become radioactive, the problem is the radioactive particles in the air. So the air entering the shelter must be filtered to prevent fallout particles from being carried inside. Some suggest that one micron filters be used but others say 90-degree turns in hallways and ducts are sufficient. A non-electric ventilation option is a Kearney Air Pump.

The doors and hatches would need to be vented to allow the cross ventilation. Low voltage fans would be needed to keep the air moving. Air would enter the shelter through the rear (smaller) entrance. It would cross the main shelter and then escape through the main (larger) entrance. Both entrances would provide a space for washing-off contamination before entering the shelter. The runoff water would need to be carried away by a drain or pumped outside since it would contain radioactive particles.

This brings up the issue of electricity. In an actual emergency the likelihood of the electric grid going down is high; so this tiny shelter would need to be completely off-the-grid and powered by external solar panels or human power. Solar panels would run the risk of being covered with fallout, so some kind of human power generator backup would need to be available. The reliance on electricity would need to be limited to lighting, ventilation, and communication simply due to the lack of power.

Another item to stock would be heating and cooking fuel. While subterranean structures naturally regulate their temperature, they are not typically warm unless some kind of passive solar heating or artificial heat source is used. In a space this small the occupants’ body heat may actually make the interior fairly hot after some time has passed. But having a way to heat the shelter with a clean-burning fuel would be a good idea too.

Lower-Cost / Multi-Function Shelter Examples

The shelter I’ve drawn here could be expensive to build and truthfully, the whole neighborhood would know you built it due to the size of the hole. So I’m guessing that most folks aren’t going to be building this kind of purpose-built fallout shelters.

I suspect most people will want something that will provide multiple functions. They’ll probably be modifying their current homes or building outbuildings with more shielding than their current homes. Here are some examples of small buildings I’ve some across in the past that would make decent fallout shelters.


There isn’t a whole lot of information out there about nuclear survival. Here are some good places to start learning.

Did I miss something?

If you’re an expert on the topic please contribute by commenting on this post. My intention is to help educate and help lessen the taboo on the topic of nuclear disaster preparedness. Thanks!




  1. O

    Great article, Michael. I’d like to add one thing. Perhaps the easiest to build survival shelter is an earthbag dome with earth sheltering. You don’t need to buy plans — the instructions are free. (But you’d have to do the research and add ventilation, etc.)

  2. Thanks Owen! Totally forgot that link. Thanks for adding it.

  3. J

    The most important point is that when all the worst possibilities have occurred (9.0 earthquake, 23 foot tsunami, loss of power grid) that NOT A SINGLE LIFE HAS BEEN LOST BECAUSE OF THE REACTORS. 20,000 plus people have been killed by the earthquake and tsunami and you are putting up articles about fallout shelters. It make way more sense to put up articles about earthquake and tsunami safety.

    People are being needlessly frightened by poor journalism and ignorant bloggers. This is inexcusable. The threat to people outside Japan is too small to measure.

    I have worked as a Radiological Controls Tech as well as Reactor Operator so I have education and experience on the subject.

  4. John,

    First you’re comparing apples and oranges… an enormous natural disaster and a human made disaster. We have a choice to close nuclear power plants, we do not have a choice to have have no more earthquakes.

    Also the effects of the first (earthquake/tsunami) create immediate effects so the impacts (deaths, damage) are mostly front-loaded. The nuclear disaster’s impact will most certainly be felt for years as cancer deaths and other negative effects emerge over time.

    People are frightened because they no virtually nothing about how to protect themselves against a nuclear threat. There is a wealth of information out there on non-nuclear disaster relief and I’ve blogged many times brainstorming solutions right here on Tiny House Design. What is missing is exactly what I’ve posted here… information that few will touch due to the taboo nature associated with nuclear power.

    I respect your years of service to the nuclear industry and imagine you must have extensive experience with the topic. But you must also admit you might be a bit biased as an insider.

    The bottom line is that non-renewable energy like nuclear, oil, coal, natural gas, are killing us. Everything we’ve built relies on it and we’re now seeing the fragility of our civilization’s foundations.

    This is humanity’s opportunity to turn catastrophe into progress and move away from these high risk energy sources, downsize, conserve, and rebuild a foundation based on renewable energy.

  5. K

    John, I agree that many people a long way away from Japan are overreacting in the light of the current situation. There is no need for people in Europe or the USA to feel personally threatened by the radiation leaking from the Fukushima reactors.

    However, I’m troubled by your statement because of two reasons:

    1st, you claim (in all caps) that not a single life has been lost because of the reactors. To which I have one word to add: YET. Radiation doesn’t work like an earthquake or a tsunami, or a bomb, for that matter; it doesn’t kill instantly. However, many people in the immediate vicinity of the reactors have been experiencing levels of radiation over the past couple of weeks that will most probably damage their health and possibly cause their death eventually. Some of the workers sent into the damaged reactors have already had to be hospitalised because of the dangerous dose of radiation they were submitted to. Your statement is still true today, but I’m not sure how it will hold up in the coming weeks, months and years.

    My second objection to the sentiment of your post is that people are not only worried because of the Fukushima plant. They are also worried because in many countries there are nuclear reactors that were built a few decades ago and don’t have the high standard of safety that they ought to have. Japan isn’t the only earthquake zone in the world, and many countries are revising whether the reactors in their own countries could withstand a similar natural catastrophe. I think that when dealing with a force that can potentially be so destructive, it’s only right to think ahead and be cautious.

    I commend Michael for his thoughts and ideas on this matter.

  6. J

    I live less than 10 miles from a top 10 nuclear war target. And I’m building a root cellar and appreciate the info as I am looking at what I can to help my family survive. Within budget mind you. Thanks for posting the info.

  7. Thanks Jeremy. If you wouldn’t mind sharing your project on Tiny House Design I’d be happy to post it – all privacy and location info would be respected of course.

  8. l

    I myself do not think a lot of the people building shelters and giving good information to others so they know how to protect their loved ones is so bad, I don’t have a shelter but am happy for those who do and I do not think the main concern is nuclear power plant fallout, I think it is probably nuclear bombs most people who build the shelters are thinking of. Those who are building please correct me if I am wrong. I do not understand why someone would take these things so personal and say that the information is to frightening, we are all adults and should be able to read about it or not, if it’s to much for someone to handle then they should not read about it. I thank those who give the information, it shows they care about others enough to take the time to do it. and the fact that I believe what the bible says gives me reason to believe it will happen.
    If Japan, the United States, or Europe retreats from nuclear power in the face of the current panic, the most likely alternative energy source is fossil fuel. And by any measure, fossil fuel is more dangerous. The sole fatal nuclear power accident of the last 40 years, Chernobyl, directly killed 31 people. By comparison, Switzerland’s Paul Scherrer Institute calculates that from 1969 to 2000, more than 20,000 people died in severe accidents in the oil supply chain. More than 15,000 people died in severe accidents in the coal supply chain—11,000 in China alone. The rate of direct fatalities per unit of energy production is 18 times worse for oil than it is for nuclear power.

  9. J

    Then visit a website providing earthquake and tsunami safety. This is safety for something completely different and has great purpose when you see the direction that this world is going. Your point is completely invalid to this topic, nonconstructive and unwanted.

  10. D

    THANK YOU MICHAEL!!! as soon as I started to read Johns post I was thinking, what is his angle here…. excellent reply to him Michael!!

  11. e

    At some point you would need to emerge from the shelter. Surviving the new reality that awaits for more than an hour would be a far bigger challenge than building a shelter.

    Consider the emotional, psychological and practical aftermath.

  12. S

    Good info. There are nuclear reactors all over the country, any one of them could be subject to an accident, terrorist attack, earthquake, or other incident.

    Many people will be shocked to discover they are still alive after a nuke attack or accident. That’s when knowledge such as this will make the difference between life and death.

  13. K

    My grandparents actually built a fallout shelter because it was part of the building code for the area in the 80s. It was just a square room in the cellar with extra-insulated walls, a thick metal door, and an air-filtration system that worked with either electricity or a hand crank (not sure how that worked, but that’s how I remember it).

    From my experience of standing in the room for 10 minutes and feeling seriously claustrophobic, these would be my suggestions for a shelter: consider that you’d have to live in this shelter for an extended period of time if you have to use it at all. Furnish it accordingly. Include board games, books or magazines and dynamo-operated flashlights in the inventory of the shelter. Check the expiry date of stored food at least once a year and make sure it’ll still be edible if you ever end up having to use it. Consider a way to have a working radio in the shelter (maybe have the antenna go through the air vent?), or how will you know when it’s safe to get out?

    Btw, Michael, I like how you actually have an extra room for the toilet. My grandparents had a chemical toilet standing in the corner of their shelter, with a shower-curtain around it. I think that would not be the most desirable option. I’m glad we never had to use it.

  14. M

    You left out corrugated steel pipe.

  15. p

    What about concrete pipes normally used for sewage drainage?

  16. As someone who has studied this stuff forever I only have a couple of complaints about your design.

    The biggest one is floor space. In the war scenario, you’re gonna be stuck down there for a minimum of 2 weeks. You’ll need to be able to move around freely just to keep your health and sanity. Not a big deal in a tiny house because you’re free to go outside, but try not leaving a tiny house for two weeks or more.

    The second is for the best radiation protection, the shelter should be at least 8 feet underground at the roof.

    My final thought of course is to bear in mind while this would make an excellent fallout shelter, it is by no means a blast shelter. It’ll work great as long as you’re nowhere near a target. The earth arching you have in the design will help, but being constructed of concrete (even reinforced) it’s not the best design to mitigate ground shock. If that concrete cracks (even if it didn’t fail and collapse) you’d have groundwater flooding the shelter. Which would force you out into the fallout.

    The best blast shelters are made from either fiberglass or corrugated steel, and are designed to flex some under ground shock conditions. Utah Shelter Systems and Radius Engineering would be great examples of blast shelter manufacturers.

  17. Malcolm Wells made a number of underground house designs which could be easily adapted for this purpose. If you’ve got a stick-built house with a basement, consider putting on a steel roof with a water pipe at the top, so you could wash fallout down the roof, into the gutters and into a cistern. That would help considerably.

    Here’s a link to Malcolm Wells’ designs, any of which would make a good fallout shelter due to the reinforced concrete roof with earth covering:

  18. M

    Well no one really knows how long would one need to stay in the shelter, could be 2 to 3 weeks or months on end or maybe a year or two maybe more who knows. You need water, food, air purifire, power, books, so on, and would one go mental living in a combined space or sharing with someone else, would you start to hate each other after a time couped up with each other, and for keeping one clean having a wash, i spent one week in the bush without having a wash, i tell ya I stunk, and you need the water to do that, I am not putting shelters down in anyway I would love to have one, The cost to build one is not in everyones pockets, this is just something to think about.

  19. J

    I see your point but by the point where you need to use this shelter, just think. You’re probably not going to care. You’re probably thinking more about your friends, loved ones and the rest of your community outside the shelter who are more than likely dead. When it comes down to survival, this will suffice the uncomfortable duration.

  20. J

    I found your article very interesting and informative. I liked the links. Thank you
    . I have bookmarked it for future reference.

    I worked in the industry but not from a reactor operational standpoint. I worked in the military on the weapon side of things. Many of my friends did work in the reactor operational side and, even though the reactor operation field and the weapons field both deal with radiation challenges, I can tell you that the information distributed, and the information necessary to do the job, is dramatically different from one filed to the other.

    Something you may look into: your comment
    “Air itself doesn’t become radioactive”
    had me thinking of radioactive iodine-131 , a gas, which is not filtered from the air by shelter filtration systems and would be (or should be) of concern to anyone seeking shelter from a nuclear weapons detonation. Just something to think about

    Concerning your comment: “the whole neighborhood would know you built it due to the size of the hole”.
    While that is true, the construction can be somewhat hidden. A person can build a shed, garage, pool, etc. . . .and tell neighbors that the extra construction is due to obstructing rocks and buried stumps that require removal.

    Or a person could tell neighbors that you are increasing the size of your basement with the intent of adding an addition to your home, down the road, when more money is available. Just do not tell your neighbors that the basement addition has 2 foot thick walls and hardened blast doors that would be found on a bunker.

    I think that the Swiss have a good handle on things. They require all new construction to include a shelter.

    Other interesting (put you to sleep) reads and links on the subject:

    “The effects of nuclear weapons”
    It is very expensive now to obtain the hard cover but it is in public domain and can be had for free on the internet. (I obtained the hard cover before the internet was available)

    The following seems to be a slide show of very interesting information that gives an good and quick overview of info from long and sleep inducing read “The effects of nuclear weapons”

    “Structure Shielding Against Fallout Gamma Rays From Nuclear Detonations” (NBS special publication 570) has a great deal of good information. This book is also an expensive hard cover book but it is in public domain and is available for free download on the internet. (yes I have the hard cover of this too)

  21. M

    I am building a room in my basement to serve as a walk-in safe/ storm shelter/safe room and decided to do some research on fallout shelters to see what I can do affordably to improve this shelter. I found an article on packing concrete bricks between the floor joists to provide more mass to provide additional protection from fallout. I am also going to be remodeling the bedroom above it. I was wondering how much fallout protection would be provided if I put some 1/16″ sheet lead down on the floor of the bedroom prior to installing a floating wood floor.

  22. Hi Mike. I found this chart handy when calculating the actual protection with various materials.

  23. M

    doesn’t appear that sheet lead will do much good then

  24. N

    Thanks for the links/info. Anyone reading this would hopefuly be doing so while thinking about preparedness. Theuy won’t build a shelter and not stock it, nor will/or should they build something made out of rice paper. If you live in tornado prone area, your home should have a shelter. If you live in an area where hurricanes or earthquakes are prevelant you need to have food/water for you and your family. We have seen, time after time, Katrina, Sandy, etc. The government will not be able to help you. you need to help yourself. If you use your “fall out shelter” as nothing more than a storage room/wine cellar, then at least you where prepared. But better that, than being the one with 2 days of food and water in your house when disaster, no matter what that may be, strikes!

  25. y

    here is israel most construction is from some sort of concrete, often (apperantly) reinforced by steel grids crisscrossing the entire structure. (outside thickness seems to me to be around 6 inches to 1 foot depending, sometimes in excess of a foot and a half)

    but I’m still trying to figure out what that means for fallout protection.

  26. 1 foot of concrete is 5 halving thicknesses. 10 halving thicknesses is usually the normal minimum for fallout shelters. A halving thickness is the amount of a material that can cut the radiation passing through in half. For example 3-feet of dirt and 2-feet of concrete provide 10 halving thicknesses.

    Learn more here:
    Also see this chart to see a comparison of actual penetrating radiation through various walls:

    If a terrorist nuke were detonated in Israel many people would survive. Ground bursts yield fallout. Air bursts have wider blast zones.

    If a missile is used and it’s detonated above the ground the blast zone will be wider but the fallout will be minimal. So if you’re outside the blast minimal radiation shielding will probably be ok.

    If it’s a ground penetrating missile aimed at a hardened target, or a terrorist nuke trucked to the target, there will be fallout downwind of the blast. In that case get behind as much shielding as possible and stay there for at least 3 days.

    That half life of fallout is measured in hours not years so it drops to safe levels very quickly. Avoid ingesting, hailing, or touching fallout. On your skin it can burn, inside you it may be fatal.

    If you’re curious to see how wide of an area can be affected by a nuke try using this tool: Pick the city, size of weapon, select ground burst and show fallout.

    You might also find this website useful:

    Must be tough times in Israel right now… hang in there! Nuclear war can be survivable.

  27. O

    Nuclear power isent the problem, no matter how bad the accident is the contamination isent going to be that serious. Chernobyl which was alot worse than fukushima, has killed 50 people in 29 years. And the chance of death gets lower every day. There are no increase in malformed children(this is also true for hiroshima and nagasaki, there are a 70 year ongoing study of the victims)
    And it would be perfectly ok to move back into chernobyl at the moment. But in the events of nuclear war, the shear amount of radioactive dust in the air, would kill anyone who isent living underground for the first two weeks. Comparing nuclear power accidents with nuclear war is dumb, especialy since we need nuclear power more than ever, since solar and wind wount be replacing coal any time soon

  28. D

    You are completely deluding yourself regarding Chernobyl, Hiroshima or Nagasaki. The half-life of the types of radioactive isotopes that are produced in a nuclear plant meltdown last from decades to centuries. The area around Chernobyl won’t be safe to inhabit for generations. They have only recently started allowing large numbers of tourists in – but then only for the day and under supervision. Workers at the plant are carefully monitored and reach their lifetime limit fairly quickly.

    Since the half-life of isotopes created during a nuclear detonation are different, you can re-inhabit the area with no protection within weeks. You can even leave a shelter for brief periods after 3 days. This is why Hiroshima and Nagasaki have been rebuilt and are active cities today.

    As for deaths from all 3, there have been thousands of deaths due to cancer and infant deformities. It doesn’t take much time on the internet to find that information.

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