Underground Bunkers Shelters, Fortified Eco, Hardened Homes

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Hardened Structures Operates Globally Including USA, Canada, South America, Europe, UK, UAE, Asia, Australia & New Zealand. Constructing a more secure future for you, your family, friends, corporates and governments. Make my enquiry to Hardened Structures. Email : Clarry@HardenedStructures.com.au www.Linkedin.com/in/IanClarry Hardened Structures USA www.HardenedStructures.com

Undergound Bunker Shelter Companies : Hardened Structures

Brian Camden Radio Interview Transcribed & On You Tube

"Brian:  Well, we're mainly architectural engineers. We do all types of constructions, hardened shelters, as a sister company of Powell Management, which is an East Coast construction program management firm. We first started into the bunker construction, back in 1991, in response to a specific request from a client who wanted a shelter built in upstate New York. At the time, we couldn’t find anyone to do it so we kind of fell into it. We were already in / we build large capital and public projects; everything from schools to wastewater treatment plants. So we were fairly well-versed already in reinforced concrete and large earthwork operations in structural steel. We started, like I said, right after the first Gulf War in 1991. We were into all kinds of things - everything from real estate development to shopping centres. Six, seven years ago, it really has taken over the firm. We are licensed importers of war materials - we can bring in all the chemical, biological, radiological filters, and we have a license from the US State Department that allows us to work on bunkers overseas. We have about 12 affiliates, coast to coast, here in America. We have a large European operation, operation in Great Britain and an office in Bahrain. We've opened offices in Australia and New Zealand.

A hardened structure, a reinforced underground concrete bunker, it's going to run anywhere from US$200-$600 a square foot, depending on the protection program and the level of electromagnetic pulse protection, where it's located - if it’s up in a mountain, the geotechnical conditions we'll encounter and the owner's privacy and secrecy requirements. About half of our business is reinforced structures, fortified homes for people who are mainly preparing for economic collapse - this is what the protection programs are all about. And I'd say, probably 55% of our work, these are houses like you see in the interactive video.

The homes look like a regular house. They're ballistic rated, usually to a UL rating of 5, which is one round of an AK-47. They are fire resistant; they have an underground bunker component. Most of the time, they are secondary residence for a client. The good thing is that in most foreign countries, they all want American engineering. And we design everything to DoD Department Of Defence specs but generally speaking we always have to team up with a local general contractor, either a Jordanian contractor, Saudi or Turkish -- because their labor costs are so much lower. Certain clients have a protection program that envisions a tidal wave going overhead. And under that threat event scenario, what we calculate is the finish grade elevation of the area outside, be it a mountain or plain or where you are. And if it's a 1000-foot tidal wave, you have to calculate how many hours it's going to take for the water to recede. Whether it’s a 100 hours, 500 hours or whatever the time may be and you have to install CO scrubbers and oxygen machines.

Interviewer:  Interesting."

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Safe, Secure and Confidential Fortified Homes

At Hardened Structures we have over 21 years experience designing and building military-grade survival shelters, communities and fortified homes. Our extensive engineering expertise means that every project we are involved with meets the strictest requirements of Safety, Security, Building Code Compliance and utmost project Confidentiality.


We employ a Balanced Survivability approach which ensures that no single point of failure is overlooked (there is no achilles heel). We can design a newly-built or modify your existing facility to withstand a broad range of threats including: natural disaster, blast/ballistic, CBRN, EMP/HEMP or any end-of-the-world scenario.

Ask us about how our methodology can help you!


Our team are experts at analyzing all forms of security threats, from simple home-invasions to full-scale terrorist assaults. Drawing on experienced ex-US Navy SEALs, Security Experts and Construction Professionals, you can be assured that our services will help you respond to any security or threat event scenario.
Challenge our team - we can provide you with a solution for any threat scenario.


All of our projects are handled with the utmost discretion, confidentiality and secrecy. We are experts at covert construction and clandestine contracting techniques along with utilizing disguised bid packages to ensure that no-one but the client recognizes the true potential of any facility.
Contact a Hardened Structures representative to find out more!

Our Services

  • Design Services:
  • Full Architecture Design
  • Shelter Programming
  • Shelter Dynamics
  • Existing Shelter Evaluations
  • Structural Engineering
  • Blast & Ballistic Engineering
  • Mechanical Engineering
  • Electrical Engineering
  • EMP/HEMP Mitigation Engineering
  • CBRN Air Filtration Systems
  • CBRN Sensors and Monitoring
  • Hardened Alternative Energy Systems
  • Hydroelectric, Solar, Wind and Geothermal

  • Construction Services:
  • Construction Management
  • Construction Supervision
  • Covert and Clandestine Construction
  • Owner’s Representation
  • General Contracting
  • Quality Control Programs
  • Budgeting & Cost Estimating
  • Critical Path Scheduling
  • Permitting and Plan Approvals
  • Shelter Commissioning

  • Security Services:
  • Threat and Risk Assessments
  • Defensive and Offensive Plans
  • SEAL “Red Team” Evaluations
  • Armored Vehicles
  • Personal Combat and Firearms Training
  • Post Attack Recovery Plans
  • CCTV, Infra red, numerous electronic sensors

  • Manufacturing Services:
  • Blast and Ballistic Doors
  • EMP/HEMP Resistant Enclosures
  • Ballistic Rooms and Buildings
  • EMP/HEMP Shielding Systems
  • EMP/HEMP Resistant Data Centers
  • EMP/HEMP Resistant Electrical Generators
  • Above & Below Ground Tornado Shelters
  • Escape Tunnels and Hatches
  • Ballistic Rated Firing Positions
  • Guard Shacks & Observation Shelters

Bug Out Planning : Living Off The Grid : Survival Blog Post

Letter Re: Prepper Axiom #5

"Dear James and Hugh,

Your writer of the day for June 20th brought a smile to me when I read his comments on the fallacy of “bugging out”. This topic is one that is near and dear to me, both personally and professionally as the design director for Hardened Structures and as a former infantryman and Boy Scout. Even with my training and experiences (or especially because of this training) it’s really inconceivable to me to think of providing 2,000 calories per day, every day for my family of four indefinitely, out in the boonies, with only a pack and a rifle, without at least a small plot of land to develop into a micro farm of sorts.

One of my own axioms with clients who ask about bug out planning is: “History has been very unkind to refugees.” So you better have a really well planned place to go and establish life ahead of collapse and not be rejected by the locals. This takes time, being on site personally, and not just a “retreat” that you do not habitat on a regular basis. This usually gives most people some pause, and to those who still really think they are going to be Rambo or Daniel Boone while bringing along the women and children, I mention, “The state of California allegedly has about 480,000 deer roaming about, while the human population is 50 million. Think about how that ratio works out. Who will get those deer? Would it be out-of-towners or the locals who know the terrain?”

However, I am also no advocate of staying put in an urban center during an extended grid down event. I do not know what a future collapse will look like, but we know for certain how things look right now in Venezuela and how New Orleans looked during Katrina and the USSR during the WWII Siege of Stalingrad. – In Stalingrad, the city was cut off from all outside support by the Nazi siege during the winter of 1942-43. After the food ran out, people ate all the birds, rats, squirrels, et cetera, and then later went and dug up the bones from these to mix with even sawdust to make some form of soup or gruel. After that, it was not safe to let your children out of sight, as cannibalism was rumored.

This horrific topic always seems to be the end game of extreme starvation– cannibalism. It’s even mentioned in the Bible on more than one occasions.

And there was a great famine in Samaria: and, behold, they besieged it, until an ass’s head was sold for fourscore pieces of silver, and the fourth part of a cab of dove’s dung for five pieces of silver. And as the king of Israel was passing by upon the wall, there cried a woman unto him, saying, Help, my lord, O king. And he said, If the Lord do not help thee, whence shall I help thee? out of the barnfloor, or out of the winepress? And the king said unto her, What aileth thee? And she answered, This woman said unto me, Give thy son, that we may eat him to day, and we will eat my son to morrow. So we boiled my son, and did eat him: and I said unto her on the next day, Give thy son, that we may eat him: and she hath hid her son. And it came to pass, when the king heard the words of the woman, that he rent his clothes; and he passed by upon the wall, and the people looked, and, behold, he had sackcloth within upon his flesh. – 2 Kings 6:25-30

Therefore the fathers shall eat the sons in the midst of thee, and the sons shall eat their fathers; and I will execute judgments in thee, and the whole remnant of thee will I scatter into all the winds. – Eziekel 5:10

Our family, having left urban life in 2013, see daily how utterly foolish our “expertise” was at being preppers in a suburban environment. If you want to have any hope of survival in a post “grid down” event, one needs to either have a very robust, well stocked, and expensive bunker (well over $200k) or be established in a rural location with a home that is capable of operating in an off-grid mode. In the years since we moved out of the city, we are daily reminded how the local folks’ daily life skills so far exceed our own. Folks’ daily life includes raising small livestock for food, gardening, handyman skills, logging skills, hunting and fishing skills, and more! Some are things which my wife and I do have some background with from our childhood, but WOW! How much more the local, life-long rural folks know, and it’s not considered anything special. It’s just life to them. We are learning fast and making great connections by showing respect for our neighbors and being willing to laugh at ourselves with them about what we don’t know when they show us a better way.

Today our children know food comes from plants and animals on our property and around the neighborhood and not just packages in the store. The four year old knows when fruit is ripe to pick and how to tell a black widow from a crab spider and is happy to pick up worms she finds to put in the compost bin. I spend far more hours with a garden hose watering plants or a pick-axe planting more food plants or a come-along hand-winch stretching 100’x6’ horse fencing rolls than I do with a rifle or pistol on the range, but we do have a small makeshift back yard 25-meter range, so practice is just a 100-yard walk back to the fence line, and the orange painted steel discs attached to sawhorses are great advertisement that we are armed and skilled. Blackberries and plums are in season here in Oregon right now, and we have filled 5-gallon homer buckets of each, just in the last two days, with more to come over the next week or so. The blackberries are headed for the freezer, and plums will be cut in half and put in the dehydrator. These will last all through the next winter and beyond.

You can survive four minutes without clear air, about four days without clean water, and about four weeks without food. Be somewhere the air is clean, the water comes from your own property, and you can grow at least some of your own food. Even without a collapse ever happening, it has become the best possible “little life” I could ever imagine for raising our children and escaping the daily stress of the urban life. – D."

Luxury Off-The-Grid Survival Retreats : FORTIFIED & HARDENED Homes

Survival Retreats : Ready to Build Or Retrofit your Home / rural Homestead?

Regardless of your budget there are physical improvements that can be completed on an existing home to bring a higher level of overall protection.
Most of our clients seek to renovate an existing home and outbuildings, rather than build. Although building from the ground up is the best overall choice, many times it can be more economical to simply retrofit a property into a secure homestead. If you're looking to build a truly safe and sustainable retreat from the ground up, you have found the right place.

Douglas Clark is our certified Hardened Structures architect. He will design everything from a small safe storage room, defensive fighting positions all the way to a fully integrated shelter capable of surviving a nuclear detonation within 10 miles, and everything in between.
The fees for the retrofit and design work are well within the scope and means of our average clients, so don't be leery of speaking with Douglas and his Hardened Structures Team.
In each custom consulting package, time is allotted to speak directly with Douglas about your plans in order for you to ascertain the feasibility of the improvements you're seeking in the new rural homestead.


Because it is impossible to protect against all threats and hazards, adopting a balanced approach in designs that considers intended functions, threat mitigation and budget is imperative. There is no one-size-fits-all and there is no formula of security features and programs that will ensure 100% safety against all violent attacks or natural disasters.
Designers and owners must understand the limitations of designed facilities and proposed countermeasures. Mitigating measures or countermeasures are specified to meet a particular anticipated threat, not all possible threats.
Douglas and his team design your facility to achieve a Balanced Survivability, ensuring that no one system or component is the "Achilles heel." No matter if it is a regional natural disaster, nuclear and/or EMP event, armed assaults, or any civilization altering scenario, our experienced teams of architects, engineers and project managers can design and construct your facility efficiently, covertly, and cost effectively.
  1. Client Interview/Site Assessment
  2. Feasibility Study "Personal Protection Plan"
  3. Client Feedback on Protection Plan
  4. Project Program Design Narrative
  5. Design Documents
  6. Client Review/Comment/Approval of Design documents
  7. Technical Construction documents and equipment specification
  8. Construction Management Planning
  9. Pre-Construction; bidding, coordination, staging, equipment ordering
  10. Permitting (if requested)
  11. Construction
  12. Client Move-In
  13. Systems Orientation


Hardened Structures are designed to perform its PRIMARY MISSION both during and after a war-like or criminal attack, a major natural disaster, or accidental/man-made emergency. Douglas and his team address these challenges by employing a Multi-Hazard Engineering methodology in the design and planning stages that not only recognizes individual hazards/threats sequentially, but also address all hazards/threats simultaneously as a problem of optimization under constraints. A Hardened Structures facility can be designed to protected against a wide range of threats including:
  1. WMD's
  2. Frontal Assault and Forced Entry
  3. Economic Collapse / Breakdown of Law & Order
  4. Anarchy Ballistic / Blast Protection / Major Earth Event (Life Ending) Cataclysm
  5. Chemical, Biological, Radiological, Explosive (CBRE) agents
  6. Airblast
  7. Ground shock
  8. Fragmentation and damage to the structure and equipment due to explosive loading
  9. Penetration

Hardened Structures Design Planning

Hardened Structures Threat Mitigation

Hardened Structures Construction Methods

Fortified And Hardened Homes - Products And Services

Fortified & Hardened Homes

Hardened Structures is a Professional Design & Construction Program Management Firm specializing in the confidential planning, design and covert construction of fortified homes (or conventional homes) with underground shelters or bunkers (shown above), stand alone shelters and other types of sheltering options. These facilities are designed with independent sources of power and water. They can serve as a primary dwelling, vacation home, retreat, long term shelter or expanded multi-function compound. Client confidentiality and total project secrecy are paramount on all of our projects.

Our Team comprises of a core group of independent design firms and general contractors with specialized training in the unique design and construction requirements of Fortified Homes.

Balanced Survivability Design Approach

Because it is impossible to protect against all threats and hazards, adopting a "balanced approach" in designs that considers intended functions, threat mitigation, and budget, is imperative. This is where Hardened Structures experience and know-how separates our Team from the general purpose Architects and Engineers. Our Teams experience has shown there is no one-size-fits-all or formula of security features and programs that will ensure 100% safety against all manmade or natural disasters.
In order to meet our client's goals and budgets, our Team ensures each project is designed and specified to meet a particular hierarchy of anticipated threats, not all possible threats. In other words, Hardened Structures' Team designs your facility to achieve a Balanced Survivability, ensuring that no one system or component is the "Achilles Heel". No matter if your personal threat hierarchy focuses first and foremost on a regional natural disaster, Nuclear, Biological, Chemical or EMP/HEMP event, or forced/armed entry; our experienced and highly specialized team of engineers, scientists and ex-Navy SEALS can confidentiality design and covertly construct your facility efficiently and cost effectively.

Traditional American executive home architecture has a number of pitfalls which are detrimental to secure home planning.

We advise some sound planning principals for hardened home design which are contrary to the typical executive home plan, but very favorable to making the home much more ready to protect families in a crisis event.
One key design concern is a master suite separated far from children's bedrooms, often on the opposite site of the home, past the main entry, combined with a grand open plan main entry to great room layout ( 70% of home invasions occur through the front door ).
All humans natural reaction is to personally go secure their children in an emergency.
Therefore one can easily see how a home with the master and children's bedrooms separated by the main entry is a major design flaw in secure home design in event of a home invasions, (or even in a tornado or fire or earthquake).

Fortified And Hardened Homes

Secure And Elegant Fortified Homes

At Hardened Structures our architects can design to your individual architectural style be it Contemporary, Traditional, Colonial, Mediterranean, Beach Front, Southwestern or any personal preference.  We can also work with your own architect to achieve the level of protection and perfection necessary for your personal residence.  Our security consultants are internationally recognized experts in the fields of building fortifications, personal security, advanced security systems and offensive/defensive components.

At Hardened Structures we employ a Multi-Hazard Engineering methodology that not only recognizes individual threats sequentially, but also address all hazards/threats as simultaneously occurring, so as to insure there is no "Achilles Heel" within our designs.  The Protection Program for a Fortified Home is varied and is usually determined by the Client's Threat, Risk and Asset assessments.
The home can be protected against a wide range of threats including forced entry/assaults, climate change, chemical / biological / radiological / explosive (CBRE) agents, air-blast, ground shock, penetration, fragmentation and damage to the structure and equipment due to explosive loading.  Along with the Client's particular living, function and storage requirements, the designs also incorporate active offensive and defensive components, and mechanical responses to reduce the effectiveness of any given threat while providing for individual/family long term living requirements.

Fortified Homes are special, and so are the people who choose them. At Hardened Structures confidentiality is paramount.  We serve as our Client's agent, representing their best efforts by professionally and stealthily implementing a design/build program to meet any Threat Event.

Fortified Homes can include protection mitigation for:

  • Natural disasters covering earthquakes, hurricanes, tornadoes, lightning and flooding.
  • Ballistic Levels for most weapons from .22 to .50 caliber
  • Forced Entry and Armed Assaults
  • Fire in the immediate surroundings
  • CBRN (chemical, biological, radiological nuclear) air filtration systems
  • EMP/HEMP shielding and mitigation
For most of our clients, one of the most important aspects of designing their Fortified Home is that it not resemble a fortified home and that the outwardly appearance is of a well designed custom home.  Only the owners will know the true capabilities and functions of the home which may include:

  • Vaults for firearms and ammunition
  • Vaults for precious metals, cash and other vaulables
  • Remote control Offensive and Defensive systems
  • Hidden compartments and sliding bookcases
  • Emergency escape ways
  • Alternative energy and sustainability systems
  • Vehicle storage and fuel systems
  • Ballistic walls, windows and doors
  • Fire resistance
  • "Off Grid" electrical capabilities
  • Independent water and sewage
  • Advanced security systems, CCTV, sensors and alarms
  • Hidden passages and entrances
  • Underground bomb shelter and storage

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LSR Luxury Survival Retreats

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FORTECO Fortified Eco Homes Hardened Structures


The enhancement of preparedness properties through the seamless integration of water features, alternative energy and food production systems with discreetly designed tactical positions.

The integration of these key features provides the foundation for a sustainable and defensible retreat property.

As preppers we are all seeking abundant water, alternative energy creation, sustainable year round food production, on a highly defensible property. These attributes are the pillars of retreat property scouting, however, how do you implement all these aspects into a seamless retreat development plan that not only makes sense, but stays under budget?
Before you start making calls and buying equipment for your property, you'll need a well thought out design. The questions are endless; How to clear a spot for the solar panels yet keep certain trees and bushes for cover and concealment? Can the tail-water from the hydro be used to form a water feature that acts as a terrain obstacle for threats? How about a combination swale and Hugelkultur bed to form a vehicular barrier both at the entrance of the retreat, but along the extended driveway as it winds along several curves designed for ambush points, and food production.
The landscape design division of Survival Retreat Consulting can tackle these tough answers and help you move into the  design and retrofit stage, and as you'll find out it's the most exciting and rewarding stages of your new property ownership.

Defensive positions should be seamlessly integrated into the surrounding terrain.








Services Include: Natural Camouflage Plan, Construction Documents & Details, Permit Application & Approval Assistance and Property Improvement Visualization through CAD renderings

Survival Retreat Consulting

Black Rifle Real Estate Company

"We highly recommend Hardened Structures to all our clients!
From safe room design all the way to million dollar bunkers,
Hardened Structures does it all. If you're looking for ultimate
in quality and OPSEC, give them a call!" 
Black Rifle Real Estate https://www.facebook.com/blackriflerealestate

Survival Realty


American Redoubt Realty

Image American Redoubt Realty

Build Fallout Shelters, Bomb Shelters and Bunkers

Underground & Above Ground Bunkers : Fallout Shelters : Bomb Shelters : Threat Assessment : Selecting The Location : Design Of An Underground Bunker : Occupancy Duration

Hardened Structures, Virginia Beach, USA constructs underground or above ground bunkers and fallout shelters ( also fortified homes and defensible off the grid luxury survival retreats ) which are individually designed to our client’s protection program and long term survivability requirements. Although the designs and systems are principally determined for nuclear weapons, it can be stated that a well built nuclear bunker also offers good protection against CBRE (Chemical, Biological, Radiological and Explosive) weapons and natural disasters. An Underground Bunker can be designed and constructed in most locations be it rural, suburban or inner-city.
Bunkers, Fallout And Bomb Shelters
Underground bunkers are advantageous for several reasons; they provide the added protection of being below the surface thus escaping a major portion of the effects from blasts and radiation, they can be pre-stocked with provisions to sustain their occupants for several months and, most important, they can be located connected to, or adjacent to, a client’s primary residence, thus allowing for quick evacuation.
The bunkers can be designed for either Single Use or Multi Use. A Single Use bunker is used only in case of an emergency and is a stand alone design. The advantage with the Single Use if that may be readily accepted by the local building authority having jurisdiction because it is not required to provide normal every day accommodations for people.
A Multi Use bunker can be used for other purposes (i.e.; store rooms, wine cellars, etc.,) and this ability is sometimes more appealing to our clients. However, it must then be designed to accommodate everyday ingress/egress and building code requirements.
Bunkers, Fallout And Bomb Shelters

Threat Assessment

A sudden all out attack by the Soviet Union or other country on the U.S., as envisioned during the Cold War, is now highly unlikely. The recent National Planning Scenarios ( Attack Scenarios ) compiled by the Department of Homeland Security identifies a Nuclear Detonation of a 10-Kiloton Improvised Nuclear Device as the most likely type of nuclear attack by a terrorist group. In this scenario, the bomb is smuggled into the U.S. where the device is carried in a delivery van and detonated in the business district of a major city. The casualties are estimated to be in the hundreds of thousands, there is total devastation from ½ to 3 miles, 350,000 people are instructed to shelter in place and contamination levels will affect up to 3,000 square miles with the recovery timeline estimated as several years. This is the primary scenario for which Hardened Structures basis its nuclear designs for Underground Bunkers. However, it should be noted that a terrorist detonation of a radiological dispersion device (RDD), often called “dirty nuke” or “dirty bomb” is considered far more likely than use of a nuclear device.
We have a variety of options for everyone’s needs and budget, contact us and our team of national experts will assist you in selecting the best underground or above ground bunker for your home.
Selecting the Location of an Underground Bunker
Perhaps the most important element in designing an underground bunker is its location or sitting. Although the threat of damage from CBRE (chemical, biological, radiological and explosive) events may be the predominant focus of the evaluation for the bunker location, additional threats may exist from forced entry, tornado, hurricane, flood and seismic events, therefore the evaluation should asses the entire range of threats to the site. It is for this reason that Hardened Structures employs a Multi-Hazard Engineering methodology.
The position of the underground bunker must satisfy the structural requirements from the shelter standpoint along with the evacuation criteria of the client and the protection programming of the mechanical systems. The immediate location and easy accessibility of a bunker has a significant bearing on its life saving ability during a crisis. Therefore, we recommend that all potential users should be able to reach the bunker within 5 minutes, and the bunker door should be secured within 10 minutes.
Generally stated, an underground bunker should be located:
  • As deep underground as possible to protect from radiation, flying projectiles and debris.
  • Outside of areas known to be flood prone, including areas within the 100 year flood plain.
  • The bunker should be placed so that the evacuees have a short route to the entrance.
  • Away from any potential debris field and its emergency exits and air inlets can be extended on several sides of the building into zones that are free from debris and fire.
  • The bunker should have as much of its external walls against the ground as possible for protection from heat and for support provided by the surrounding soil.
  • Away from potential fuel concentrations, flammable materials, vehicles and hazardous materials.
  • Away from large objects and multi-story buildings, light poles, antennas, satellite dishes or roof mounted mechanical equipment.
  • The bunker should be made easily concealed.
It should be noted that the vast majority of deaths in basement shelters during WW II were caused by carbon monoxide poisoning; the occupants had become trapped in the shelter, rather than from penetration of the shelter itself. The entrance to our underground bunker is composed of the entrance way to the bunker, the debris protection for the door, the armored door, the air lock and, in some instances, a decontamination room. In addition to the main entrance way, all Hardened Structures underground bunkers are designed with either one or more of the following Emergency Exists:
  • Escape Shafts that lead through the bunker shell/wall directly to the outside and then run vertically up the bunker wall.
  • Escape Tunnels run horizontally away from the bunker for a distance of one and one half times the building height to clear any fallen debris.
  • Escape Chimneys that are air and blast proof emergency exits which lead up through the expected pile of debris from a collapsed structure. The chimney must be constructed to a height of at least ¼ of a buildings height when measured from the eves.
Design of an Underground Bunker
An underground bunker may be as small as a 10’ x 10’ room designed to preserve life with little or no comfort, to a multi-cell shelter housing hundreds of occupants with a storage capacity for years. Access is an important element of bunker design. If obstructions exist along the travel route, or if a bunker is cluttered with non-essential equipment and storage items, access will be impeded and could cause chaos or panic. It is imperative that the route to the bunker remain unencumbered to allow orderly access.
Bunkers, Fallout And Bomb Shelters
In the scenario described above where a 10 Kiloton Improvised Nuclear Device is detonated, the design for an underground bunker is driven by the need to protect from blast loading, ground shock, nuclear radiation and fire. A detonation involves supersonic combustion of an explosive material and the formation of a shock wave. The three parameters that primarily determine the characteristics and intensity of blast loading are the size of the explosives, the type of explosives and the distance from the point of detonation to the bunker.
A detailed analysis is required to determine the magnitude of pressure and impulse that may load each surface of the bunker relative to the origin and type of the detonation. For these reasons we generally utilize reinforced concrete. Reinforced concrete is a composite material in which the concrete provides the primary resistance to compression and shear and the steel reinforcement provides the resistance to tension and confines the concrete core. In addition to ductile detailing, which allows the reinforced members to sustain large deformations, reinforced concrete also provides inertial resistance as well as the continuity of cast in place construction facilitating designs that are capable of withstanding the high intensity and short durations of blast loading.
When designing for radiation and fallout, it is difficult to predict the intensity of radiation within a specified area. Radioactive fallout distribution depends on such variables as the type of burst, amount of energy released, height of the radioactive cloud, nature of the ground surface and the speed and direction of the wind at different altitudes.
Bunkers, Fallout And Bomb Shelters
There are three types of radiation in fallout: alpha particles, beta particles and gamma rays. Alpha and beta particles are easily shielded however Gamma rays are not easily attenuated. They are similar to X-rays and are capable of penetrating a considerable thickness of even dense material.
After residual radiation the next most widespread effects are the thermal radiation and related fires. If an underground bunker is located under or adjacent to a wood frame home it must be assumed that the house will catch fire and be totally destroyed. In this scenario a bunker ceiling constructed of 16” of 4,000 psi concrete together with walls of 12” and floors of 8” is required.

Protection against airborne chemical, biological and radiological (CBR) agents or contaminants is typically achieved by using particulate and absorption filters in series and providing for positive internal air pressure. There is no single filter which can protect against all CBR materials. All air flow passes through installed filters of the HVAC system. The exterior air intake and exhaust openings in the bunkers are all protected by blast valves. The outer most filters are coarse, low-efficiency (pre-filters) which remove large particles and debris while protecting the mechanical systems. Chemical, radioactive and biological aerosol dispersions (particulates) are efficiently removed by HEPA filters. Sorbent filters are located downstream from the particulate filters. This allows the sorbent to collect vapors generated from liquid aerosols that collect on the particulate filter and reduce the amount of particulate reaching the actual sorbent. Sorbents have different affinities, removal efficiencies and saturation points for different chemical agents and therefore choosing the appropriate sorbent or sorbents for an airborne contaminant is a complex decision.
The Department of Homeland Security, Working Group on Radiological Dispersal Device Preparedness identifies three levels of protection that range from filtration with pressurization (Class 1), filtration with little or no pressurization (Class 2), and passive protection (Class 3). Class 1 is for a large scale release over an extended period of time and is considered primarily for a war-like attack. Class 2 protection is for a terrorist attack or technological accident with little or no warning and is characterized as a short duration small scale release. Class 3 protection is typically applicable to an industrial accident that results in a short duration.
To withstand a CBR event the bunker must be equipped with a filter-rack mechanical system capable of providing the minimum number of air exchanges required by the building code for the shelter’s occupancy classification. This will provide a flushing capability once the CBR hazard has passed and will facilitate use of the bunker for non-CBR events. For Single Use bunkers, 15 cubic feet per person per minute is the minimum air exchange recommended by the International Mechanical Code. At Hardened Structures we recommend a minimum head room of 6’-6” and a minimum of 65 cubic feet of net volume be provided per bunker occupant and we can install a mechanical system to withstand most any class of protection to meet your individual protection goals.

Occupancy Duration

Occupancy duration (also known as the button-up time) is the length of time that people will be in the bunker with the doors closed ensconced in a protective environment. This time period can last from a few hours to several days. If the occupancy duration of a bunker is less than 24 hours then sleeping areas are typically not required and the occupant load will generally be 20 square feet/person. If the occupancy duration is greater than 24 hours sleeping areas should be incorporated at the rate of 60 square feet/person utilizing single beds or 30 square feet/person using bunk beds.
The total square footage of an underground bunker is determined based on the following:
Number of persons
Occupancy duration
Class of protection
Storage requirements
The Client’s particular life sustaining/quality requirements
The duration of occupancy of an underground bunker will vary depending on the intended event for which the bunker has been designed. Protection levels, occupancy duration and specific Client storage/survivability criteria are the most important factors that influence the design process.
As stated previously, our Underground Bunkers can be constructed in most locations, rural, suburban or inner-city. The fundamental question is the level of protection the Client desires and their resources to achieve that level. A representative from Hardened Structures is available to meet and help determine Asset Assessment, Threat Assessment and Survivability Criteria and will also develop a Feasibility Report for any proposed Bunker location.
We have a variety of options for everyone’s needs and budget, contact us and our team of global experts will assist you in selecting the best underground or above ground bunker.

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