Shelter & Hardening Structural Engineering Services

Peace of mind for you and yours.

Having a deep understanding of your threat, the threat duration, and level of risk tolerance is key to developing your hardened structure, shelter, or bunker. You don’t want to hope the structure works when trouble comes. You want to know it works.

At SAI, we get that. We get that you are not going to bury a bus or shipping container. You want to do things right. Whether it is a discreet safe room added to your existing home, a large luxury bunker, or a place for your employees to go during tornado watches, you want a safe comfortable space where your family and your valuables are well protected.

Hardened structures, shelters, and bunkers don’t have to stand out. It need not be a topic of conversation every time you entertain. If you want safety and security, want it to look good, and blend with your home or office, let us join your team.

What we do.

First and foremost, we must understand the threat you are facing and how long that threat will last. We also need to know what you want to protect, people or valuables, and in what quantities. Once we have a deep understanding of your situation, expectations, and budget we will design the structural component for the bunker, shelter, safe room, or hardened structure that meets your needs. With our strategic design partners, we can also produce specifications and drawings for other trades that may not be familiar with this type of specialty design.

We understand that transporting shelters from another state and hiring the massive cranes required to unload and place them on large concrete pads represent a huge percentage of the cost of the project. We provide the documents necessary for you to get bids and permits so that you can utilize local contractors as well as locally sourced materials to save on the cost of your project. You can certainly manage the construction yourself with the information we provide if that is something you are comfortable with.

Frequently asked questions.

Q. What is the difference between a bunker, shelter, safe room, and a hardened structure?

A. There is no universal consensus on the definitions of difference between a bunker, shelter, safe room, or hardened structure. But for our purposes we’ll define these spaces as follows.

A bunker (also referred to by some as a bomb shelter or doomsday bunker) is designed to withstand an explosion and is typically associated with wartime. While explosions can obviously come from conventional or nuclear weapons, they can also come from other sources such as industrial or chemical facilities, refineries, shipyards, railroad cars, or tanker trucks. Bunkers are most commonly located underground but can be placed above ground. However, the costs associated with doing this are very prohibitive. A bunker, by its very nature, must be designed as a shelter as well.

A shelter is a safe place to wait something out for a predetermined amount of time. Disaster shelters can provide refuge from threats like lightning storms, tornados, hurricanes and more. Fallout shelters can be a safe place to wait for nuclear fallout to decay. Fortified shelters can be a place to store your valuables and provisions. Luxury shelters can be a place of sanctuary from the wife and kids. Luxury shelters can also be a place where you and your friends toast the raging storm outside. Depending on the threat and anticipated duration, shelters can be located above ground. Shelters need to provide a level of comfort and amenities in accordance with the duration of intended stay. After all, you are going to have to go to the bathroom at some point. We define shelters as permanent structures so as not to be confused with survival shelters which can be tents, ad hoc lean-to’s, etc. which are not intended to be permanent.

A safe room (also referred to as a panic room) is exactly what it sounds like. A safe room. They are typically smaller areas without windows such as closets, bathrooms, and pantries. The most common use is for tornados. However, safe rooms can be a refuge from perpetrators who are seeking to do you harm. It is the place you can go to be safe until help arrives or the threat passes. Due to their size, safe rooms do not lend themselves well to doubling as a shelter for periods of time greater than a few hours. Safe rooms are good for storing a small volume of valuables.

A hardened structure is a building or home that has been fortified against a particular threat. The concept here is to provide extra capacity, to use best practices, to do something that is beyond the minimum. A house cannot withstand a direct impact from an EF-5 tornado with winds in excess of 200 mph. But a hardened structure can withstand an EF-1 tornado with minimal damage. (EF-1 or lower are the vast majority of tornados.) If a human sets their mind on getting into your home, they will get into your home. But a hardened structure can deter or slow a person or mob with nefarious intent from entering your home.

Q. Do you provide “standard” design concepts?

A. Not at this time. Our experience has taught us that there is no one size fits all. Each situation, expectation, site, etc. is unique and we treat it as such.

Q. What building materials does SAI design with?

A. This is highly dependent on your specific needs but generally concrete, steel, masonry, wood, or a combination of any or all of these.

Q. Can I modify an existing home, office, or facility to include a safe room, shelter, or bunker?

A. Depending on your situation and expectations it is likely that we can work with what you have and modify an existing home, office, or facility to include a safe room, shelter, or bunker. While it is preferable and more cost effective to start from scratch, we recognize that this is not always possible.

Q. Can I build a bunker or shelter by myself?

A. Depending on the size and complexity, maybe. We understand the desire for discretion and lowering budgets but there is a certain level of assistance you will need no matter who you are. For example, you may need cranes, delivery trucks, excavators, concrete mixers, etc. Further, the man hours required to build a large to medium sized bunker or shelter is very prohibitive if you were to attempt such an endeavor on your own. With that said, if you are confident that you are capable of building a bunker or shelter by yourself, we can certainly provide you with the plans you need to get you started.

Q. Do I need a permit?

A. This depends on the Authority Having Jurisdiction. We will design to meet all Federal, State and Local building codes. With that said, our drawings need not advertise or give away the true purpose or capabilities of a space or structure. However, it is up to the owner and contractor to obtain any necessary permits or inspections.

Q. How do we start the process?

A. It starts with a consultation and the forging of a relationship. We have to get to know one another. We need to fully understand your concerns and desires and you need to know if we are worth your trust. The initial consultation fee is $500 for 3 hours. We can meet in person or virtually.

Full view of bunker
This luxury bunker is located off the basement of a home behind a secret door. Designed for a 1 bar (15 psi) blast pressure it is buried 42” below the ground, it has an 18” thick reinforced concrete roof, and 12” thick reinforced concrete walls. It is 10’ wide and 8’ high inside.
Bunker entry way
All walls in the entry portion are solid reinforced concrete. This luxury bunker has a mechanical room for an enclosed diesel generator, battery backup system, such as Tesla’s Powerwall, and a sump pump. A small set of stairs is required from the basement to get the appropriate amount of earth cover over the roof. Note the 90 degree turn at the entry so that radiation does not have a straight shot into the living areas of the bunker. The section before the living quarters has a decontamination shower and provides the necessary separation for refracted gamma radiation. This area also holds the grinder pump and holding tank for wastewater.
Bathroom layout in bunker
The first portion of the living quarters inside the luxry bunker has a toilet, standup shower, sink, and a place to store jackets and shoes. Next is a bedroom capable of accommodating 4 persons with the use of bunk beds.
Bunker living room layout
The living area has a kitchen, dining table, lounge, and command center that doubles as an entertainment center.
3d model of a master bedroom in a bunker
The last section has the primary bed, the food storage, air filtration system, dehumidifier, and the escape hatch. In order to contain the mess and where the water table allows, we recommend a pit below the escape hatch for the fill above the hatch to fall into. The pit is covered by an open bar grating. Where water cannot be stored outside the bunker, this portion is enlarged to accommodate the storage tanks.
Storm shelter bar from above
This underground tornado shelter is more of a recreation room.  This same concept can be placed inside a basement or as an above ground addition.   The size of the room is only limited by your imagination. 
View from entrance of storm shelter bar
Time to watch the game that keeps being interrupted by those annoying public service announcements.
View from behind the bar in storm shelter
Inherently strong and built from noncombustible materials a tornado shelter can be a great place to store your valuables.
Bar in storm shelter
Tornado shelters, bunkers, and safe rooms need not look like military barracks. They can be bright, cheery, and part of your everyday use if located and decorated properly. You are investing a lot of time, money, and effort into this space. We encourage you to utilize it.

Still want to know more.

Finite Element Model (FEM)

This is a Finite Element Model (FEM) of the custom luxury bunker shown at the top of the page. We do not speculate in our design. We let the numbers lead the way. This is what gives our customers peace of mind.

This map comes from the NOAA website. The scale on the right shows the annual average tornado warnings per year. The text at the top shows the statistics of 2011 tornado season, the worst on record. Instead of sending your employees home, why not let us design a shelter that allows them to safely stay on your premises until the threat has passed. We have successfully designed locker rooms and bathrooms as tornado shelters. Let us do the same for you.

US map showing tornado watch frequency
Tornado tracking map

This map comes from the NOAA website. It shows the tracks of all the tornados from 1950 to 2012. Instead of having to get up in the middle of the night because of the tornado sirens, why not let us design you a tornado shelter where you and the kids can have a sleepover? Or why not let us design your safe room as a place of refuge in the worst possible scenario?

This wind speed map comes from ASCE 7-16 figure 26.5-1B. If your home is near the coast where the wind speed is 110 mph or greater, you are in an area affected by hurricanes. An entire house can be designed to withstand the high winds produced by these massive storms with minimal damage. The biggest challenge is tidal surges and floods from heavy rains. We can help you achieve peace of mind that your home will still be standing, even in the eye of the storm.

US map with IBC wind figures
Map of US seismic activity

This is a heat map for seismic activity produced by the United States Geological Survey (USGS.) Did you know that the stiffer you make a structure, the more likely it is to break during an earthquake? An entire house can be designed to withstand the effects of earthquakes. With our team of experts, you can have the assurance that your home will endure a seismic event.

This map of wildfire activity produced by FEMA shows the most fire prone areas. We can design an underground shelter that preserves and protects your valuables in an evacuation.

Map of the USA showing locations of wildfires
Map showing the impact of a nuclear attack on Washington DC

This screen shot from shows the possible effects of a 5-megaton nuclear bomb, China’s current ICBM capability. According to Principals of Protection written by Walton W. McCarthy, M.E. the soviet philosophy preaches “We still meet people who have incorrect ideas about defense possibilities. The significant increase of devastating force of nuclear weapons, compared with conventional means of attack, makes some people feel that death is inevitable for all who are in the strike area. However, there is not, and can never be, a weapon for which there is no defense. With knowledge and skillful use of contemporary procedures, each person can preserve his own life as well as actively work at his enterprise or institution. The only person who suffers is the one who neglects his civil defense studies.” We can design a bunker for you if you feel that you will be inside the blast radius, or a fallout shelter to escape the effects of radiation.

This map was produced by the Armed Conflict Location and Event Data Project. Let us help you harden your home, office, facility, or structure against unforeseen events.

Map of US protests in 2020
Map of United States transmission grid

This is a map of the US electrical grid produced by FEMA. Without electricity how long would it be before things at your home or place of business became dire during a cold snap? If there was a break in the supply chain, how long could you provide for your family without immediate access to essential items? Let us design your bunker or shelter so that you can be prepared when the unavoidable or unexpected happens.

Structural Associates Inc