Above and Underground Shelters


Above and Below-Ground Shelters

Shelters offer protection from a threat or hazardous condition. Entire volumes of information are dedicated to addressing the types of potential danger that may influence you to build a shelter. Threat responses are limited only by the creative design, manufactures warranty, debris variability risks, and pocketbook of the shelter’s owner.

Shelters come in a wide variety of above and underground constructions. A shelter is a perk that can add value to your home. The typical above-ground structure is frequently a “safe room” or a fortified home concept. In fact, the FEMA Fact Sheet for Residential Safe Rooms states that “having a safe room built for your home can help provide near-absolute protection for you and your family.” That is providing the safe room has been built to FEMA standards and, of course, has been properly anchored.

FEMA guidelines are the national performance criteria for shelters. Underground constructions include modest independent bunkers to full-scale subterranean support facilities. The design of the structure is normally a reflection of personal taste or a particular survivability concept. The owner may be looking for a personal shelter in the case of a home invasion or a commune-style self-sustaining environment.

Below ground safe rooms have the additional risk of flooding, and/or debris blocking the exit. Research associate Larry Tanner from the National Wind Institute at Texas Tech University Department of Construction Engineering and Engineering Technology in an interview with 2News said, “no one has ever been killed in an approved [FEMA approved and tested safe rooms that were built to FEMA guidelines] safe room whether above or below ground.” In fact, he says that these approved and product tested safe rooms can “…handle a 3000 pound vehicle dropped on them…” and the data shows it protects even in the strongest tornadoes.

Yet, above ground safe rooms are not one hundred percent invulnerable. Many experts believe the odds for survival of an EF-4 or EF-5 tornado are better in a below-ground storm safe room shelter, not a basement because of the possible high risk of debris. The National Wind Institute tests and approves shelters built by different manufactures to FEMA standards. To check for manufactures who test their shelters, check out the National Storm Shelter Association Producer Members (NSSA) and NSSA Quality Control Process, Verification, Design & Construction, and Quality Assurance Verification.

6 Common Reasons People Build a Shelter

Threats range from the sublime, a simple storm shelter for severe weather, to a teotwayki, or the end of the world as you know it scenario. Most common threats include:

1.   Forced entry and assault: This type of shelter premeditates protection from forced entry and frontal assault, and runs along the lines of a safe room or panic room. Many contemplate building such a shelter in the context of widespread economic and social breakdown, causing the loss of substantial law and order. Not an all-too-bizarre scenario, given that small scale civil disorder has been observed following Hurricanes Katrina and Sandy.

2.   Severe weather: Protection against strong electrical or wind energy events.

3.   Biological: Primarily needed in anticipation of the release of a dispersible harmful bio-agent. Biological hardening is focused on long-term sustainability, contamination protection and filtration of air, water and other life-sustaining resources.*

4.   Chemical: With many of the same considerations as biological, chemical agents tend to present a longer active period as a threat outside the shelter.*

5.   Nuclear/Radiological: Anticipating a higher level of long-term protection, but in essence preparing for blast protection, followed by chemical and biological protections.*

6.   HEMP/EMP: This contemplates high altitude electromagnetic pulse (HEMP), electromagnetic pulse (EMP), and geomagnetic storm (GMS) effects, which have the capability to undermine and destroy electronics. When a nuclear explosion occurs, it creates an EMP. High altitude detonations would, in addition to “dirty” fallout, produce a greater range for the EMP, which is a line of sight phenomenon. For example, the detonation of a nuclear device at an altitude of 100 kilometers would expose 1.5 million square miles of the surface of the earth to the EMP.

* Chemical, biological and radioactive threats are commonly referenced conjunctively as “CBR.”

Above-Ground Shelters

The most common above-ground applications are those of a safe room or a hardened living area. In these circumstances, the protection afforded is usually a type of retreat. It allows the occupant to retract defensively and remain safe until the threat disappears or help arrives. Typically an above-ground shelter is more dependent on outside resources than its subterranean counterpart. It generally draws electricity off the normal power grid and is not independently sustaining, and will take up space from your valuable square footage of daily living area. For size limits for above-ground shelters see: Safe Rooms- NSSA.

Some advantages of above ground shelters are that they are quickly accessed. If you are moving they can be relocated. They are usually flood and damp resistant, unlike below ground shelters. You can use them like a storage shed, closet, vault, gun safe (these require an adjustment for size, and some experts do not recommend this type of use), or a safe room. They afford easy access for both people and pets and can accommodate wheelchairs. You are also less likely to become trapped by debris. They can be built almost anywhere such as a closet, garage, or pantry.

Generally speaking, above ground shelters are less expensive. But they are also significantly more vulnerable in the event of widespread physical destruction, although you can find contractors willing to engineer above-ground blast-resistant structures.

Below-Ground Shelters

These shelters range in size and complexity from single-person pods to full underground communities, complete with space for raising cattle, chickens and even a small restaurant. Typically, these units are fairly complex and carry redundant life support systems: water and air filtration, electrical generation and food generation. They can be slope front in-ground or flat top in-ground shelters. An advantage to underground shelters is that they take up little or no room from your valuable square footage of daily living area.

A below ground shelter can become smelly and damp. They also have stairs that can create access problems for some people (elderly, disabled), they could become susceptible to flooding and or the exit can become blocked by debris leaving the occupants trapped, requiring an above ground dig out to exit the shelter. Underground shelters can be built in your carport, patio, garage, or yard. Underground shelters will expose you to some risk and things that could inhibit safety such as, hail, lighting, extreme wind, dangerous flying debris and possibly blocked exits from debris. Also, they are harder to access in general. You have to go outside to get to them.

An underground unit can range in complexity from something as simple as a buried shipping container (although this is apparently ill-advised by the shipping container burying experts) to specially-designed subterranean shelters designed for military style “end of days” type applications.

Below ground structures can be mega-expensive, with the cheapest units starting around $30,000 dollars (uninstalled) ranging into the millions of dollars. Costs of digging, installation, hookup, testing and retrofitting options are extra. Some units are listed at more than $4 million dollars.

Some websites act as real estate brokers for abandoned missile silos, which you can then pay to retrofit as a fairly spacious post-apocalyptic home.

When planning ahead for your families’ welfare and safety, you need to do the homework. In addition to design considerations there are three decisions that should be made:

1.   Size (FEMA guidelines require 5 square feet per person –tornado and 10 square feet per person for – hurricane)
2.   Function (fiberglass, concrete, or metal re: load resistance…)
3.   Location

The National Weather Service-FEMA has a list of basic disaster supplies kit items to consider having in a shelter or your safe room.

Take responsibility for your safety, and the safety of the ones you love. The location, design and installation of subterranean units are often shrouded in secrecy and the owners are certainly paying for that privilege. Take prevention before the storm. Spend some time, and plan ahead. See: NSSA Articles, NSSA Industry Links.

Additional Resources




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