The best storm shelter depends on several factors, especially cost and available space.  

Available Space and construction stage


First of all is the space you have available.  If you live in the country, or are on a moderately sized city lot, you have many options, including in-ground and above ground shelters.  If you are on a small city lot, or have restrictive HOA rules, and your house has already been built, you may be limited to just above ground shelters located in your garage, or retrofit shelters under your garage.  Even if you are on a small lot, if your foundation hasn't been poured, you can install a full sized underground shelter below your garage floor prior to pouring your foundation.  

For some city lots, it is possible to still install an in-ground shelter.  Some manufacturers have a mini sized shelter that can be installed in locations that are too tight for a traditional shelter.

Cost

Typically the most inexpsnsive shelter to install will be a precast concrete in-ground shelter.  Steel and Fiberglass in-ground shelters can provide similar protection, but will be more expensive, and depending on your soil may have long-term durability issues.  If an in-ground shelter will not work for you, then you can choose above ground steel and concrete shelters, but these will typically be more expensive, and have some possible trade offs.

A typical installation of a pre-cast concrete in-ground shelter will cost around $3,500, depending on you location and distance from the manufacturer.  From there, the sky is the limit, with custom underground bunkers running into the millions of dollars.

Lets see a quick overview of the different options, and then look at each one in depth.

Type of shelter Cost Speed Safety Space Needed Asthetics Accessibility Occupancy Duration Construction Phase
Concrete In-Ground  $  1 Day High  Large  Variable  Low - Moderate  6 - 20+  1 Hr - Overnight Any 
Concrete Above Ground $$  1-3 Days  Moderate - High  Small  Moderate  High  4 - 8   1-2 Hrs Any 
Steel In-Ground  $$ - $$$ 3+ Days  High  Large  High  Low - Moderate  6 - 20+   1 Hr - Overnight Any
Steel Above-Ground  $$  1-3 Days  Moderate - High  Small  High  High   4 - 8 30-45 Min  Any 
Fiberglass In-Ground  $$$  3+ Days  High  Large  High  Low - Moderate   6 - 20+  1 Hr - Overnight Any 
Concrete Below Ground  1 Day   High  Large High  Very Low   6 - 8  1-2 Hr Pre 
Retrofit Below Ground  $$  1-2 Days  Moderate - High  Small   High Very Low   3 - 6  30-45 Min Post 
Custom Build Safe-Room  $$$  ???  ???   Small High  High   ???  1 Hr - Overnight Pre 
Custom Built Concrete Shelter $$$$ 1-2 Weeks High Very Large High Variable ???  1 Hr - Overnight Any 
Custom Underground Bunker $$$$+ ???? High Very Large High Variable ???  1 Hr - Overnight  Any 

 

 

 Pre-cast Concrete In-Ground

Pre-cast in ground concrete storm shelters provide the highest safety and affordability, quickest installation, and installation flexibility.  The shelter we install is precast concrete, with a minimum strength of 6,000 PSI.  They also have solid metal Re-Bar and fibermesh reinforcing in them.  The doors are tested and certified by the Wind Institute at Texas Tech University The seam is sealed with high quality polyurethane sealant, and the manufacturer provides a 10 year warranty against leaks in the concrete or the sealant.  The concrete provides extremelty high impact resistance and protection, in addition to being partially below groung.  There are two air vents in the top, and the door has a 3 Point locking mechanism.  Further, the door has a lift assist cylinder that means you with open or close the door with a single finger.  The shelter weights roughly 12,000 pounds, and is set about 4½' down in the ground, so there is absolutely no chance of the shelter being sucked out during even the most extreme storm.  These tend to be the most spacious for the price, allowing plenty of room to store emergency supplies.  Other styles of shelter tend to be significantly smaller for a comparable price, and will not have near as much room for storage.

Concrete Sloped Front Storm Shelter
Concrete Sloped Front Shelter

Pre-cast Concrete Above Ground

Pre-Cast above ground shelters are typically only used when there in inadequate space for an inground shelter, or a disabled person needs to be able to enter the shelter without any assistance possible. 

These share many of the same advantages of the in-ground concrete shelters, with a few provisos.  First, because of the weight, they cannot be set inside a garage, but must be outside where the crane that moves them can reach.  Further, they must be anchored to an existing concrete pad, or a new concrete pad must be constructed to anchor them to.  Because they are fully above ground, they face the full force of the wind when struck by a storm.  Thus, in an extreme EF5 Tornado, there can be more than 25,000 pounds of force against them, in addition to any impacts from debris.  This means that the foundation and anchors are of concern and potential points of failure.  Additionally, they do not have an integral floor, depending on the pad they are anchored to to provide the floor.  Should the anchor system ever fail, there would be a large opening in the shelter.

Steel In-Ground

Steel In-Ground shelters provide some impact resistance, but depend on the dirt around them to provide the bulk of the protection from flying debris.  If they are being set completely below the existing soil, or near the water table, extra steps must be taken to prevent them from floating.  Additionally, extreme care must be exercised to preven corrosion.

Steel Above-Ground

Similar to the Concrete above ground shelters, with the added benefit that they are light enough that they can be installed inside an existing garage, thus providing easy accessibility, and zero impact on the outside aesthetics of the house.  The main trade-offs are that you must give up a parking space in your garage, they have the same possible failure points in the anchoring, and they tend to be much smaller than the concrete shelters.  However, because they are inside the structure, you won't tend to spend as much time in them, as you can stay inside the house until the very last moment.  They also do not typically have floors, depending on the concrete slab to provide a floor.  If it should ever come free from the concrete, there would be a large opening in the shelter.

Fiberglass In-Ground

Fiberglass In-Ground Shelters work by providing you a hole in the ground.  The fiberglass actually provides very little impact resistance.  Fiberglass shelters typically have little aesthetic impact once fully installed because there is very little to be seen from above the ground.  However, proper installation is very important, to properly protect the fiberglass and, Very Importantly, secure it so that it does not float out of the ground in the future.  Although entry level fiberglass shelters may appear competetive on price, compared to equivalently size precast concrete shelters, they typically cost 2x as much.

Pre-Construction Concrete below ground

These are similar to the Sloped front concrete shelters, but are flat on top, and are designed to be installed prior to pouring the concrete for the foundation.  The only thing visible is the door, which tips up on hinges.  There is then a ladder down into the shelter.  This allows the area to be used to park vehicles under normal circumstances.  You will not be able to access the shelter with a vehicle parked over it.  These have several VERY BIG advantages over the Retro-Fit shelters.  These are typically larger, with 6' of headroom inside.  They also have 2 air vents that are run to outside the structure, thus ensuring ample air supply under any circumstances.  These are 5' x 7' inside, slightly smaller than the sloped front, but still roomy.

Retro-fit concrete below ground

These are installed by cutting the concrete of the garage floor, excavating a hole, suspending a steel shelter, and then pouring concrete back around it.  If you live in a neighborhood that won't allow an outside shelter, and you cant afford to give up a parking space in your garage, this may be your only option.  They have several SEVERE limitations.  First, there is no mechanism to provide ventilation from outside, and these are typically much shorter inside than the shelters installed prior to construction (because it must be moved in through the garage door, which is typically 7' tall, or less).  An inside height of just over 4' is normal.  Both of these might not be a problem if you are only in the shelter for a few minutes, but should you become trapped for several hours or longer, they could become very serious.  There is also very limited space to store emergency supplies.

Custome Built Safe Room

These are typically specially built rooms inside the house that are designed to provide privacy, ease of access, and convenience.  They require special planning and construction.  They must be structurally isolated from the rest of the house, and the foundation must be designed to provide the necessary anchoring.  They suffer the same possible failure points as all above ground shelters, but can be customized in any conceivable way.  They are also typically significantly more expensive that most other options.  For someone building a custom house that has the resources, they can provide an all in one solution for storm protection, privacy, protection of valuables, and absolute convenience

Custom Built Concrete Shelter

This would be a site-built concrete shelter.  Building on site allows you to customize the size and configuration of your shelter, if you don't find any precast shelters that suit your needs.  They have the same safety advantages of precast concrete, but will be significanlty more expensive, and quality control will be much more difficult to ensure.  If you have the financial ability, and really want something more, this may be they way for you to go.

Custom Underground Bunker

These are for the very wealthy.  The sky is the limit on these, from a simple 1 room underground bunker that would allow overnight stays to multi-room bunkers with plumbing, air filtration, and more designed to provide mediium-long term living in a host of emergency situations, from tornado to nuclear fallout and biological warfare.  Costs range from 10's of thousands to Millions of dollars.  Installation times typically run weeks to months and are typically the most disruptive to the site.  Some options allow access from concealed entrances inside the house, possibly providing the ultimate in aesthetics, convenience, privacy, and security.