Considerations for an Underground Storm Shelter

underground storm shelter

Natural disasters are a part of life in the United States, particularly for those who live in tornado alley like Oklahoma or other states throughout the Midwest. Tornados and other storm systems can cause massive amounts of damage, and if you’re not prepared, these storms can be deadly. 

One of the best ways to ride out a tornado or similar extreme weather event is inside a storm shelter or safe room. These shelters can withstand high winds, flying debris from ef5 tornados and protect you and your family from danger. But, the biggest question you have to ask yourself is: underground or above-ground? Let’s dive into this topic and see which option is best for your needs. 

What is a Storm Shelter?

The primary purpose of a tornado storm shelter is to protect the occupants from extreme weather events. However, storm shelters can work well for other situations like hurricanes or windstorms. 

Typically, storm shelters are not too big because they’re designed for temporary use. Once the storm passes, you can exit the shelter and survey the damage. That said, the interior can be spacious enough for multiple people and come equipped with supplies for a few days, just in case. For example, if a tornado destroys all or part of your home, you may need to sit tight in the shelter until you can find more long-term lodging until your house gets repaired. 

The Federal Emergency Management Agency (FEMA), FEMA 320 guide offers guidelines for a storm shelter company or manufacturer on specifications for each model type’s size, shape, and installation requirements. New construction shelters can exceed FEMA guidelines.

Underground vs. Above-Ground Storm Shelters

When picking a storm shelter for you and your family, you need to decide between an above-ground tornado shelter or an under-ground unit. Let’s break down the advantages and disadvantages of each option. 

Pros and Cons of an Underground Storm Shelter

  • Pro: Less Prone to Wind-Driven Debris Damage – The biggest threat during a tornado or hurricane is not the wind itself. Instead, it’s when the wind picks up and throws heavy or dangerous objects at high speeds. Something as small as a stick or a rock can become lethal during a storm. Underground storm shelters can avoid most debris because they’re not exposed.
  • Con: Flooding – Underground storm cellars require ventilation to ensure that you don’t suffocate. Unfortunately, these shelters are not usually waterproof, so water can seep in. Sometimes, the water can come from heavy rains caused by the storm, or a nearby pipe could burst and send water into the shelter. Some people have died from drowning this way. 
  • Pro: Easier Access in Some Situations – Most people get injured when trying to find safety, such as getting into a storm shelter. However, you can avoid this issue if your shelter door is attached to the home (i.e., through a basement or garage). This advantage doesn’t work if the storm cellar is outside and away from the building. 
  • Con: Harder Access for Those With Mobility Issues – Since the storm shelter is underground, there have to be stairs. So, getting in and out of a shelter can be challenging for those with wheelchairs, walkers, or other mobility issues. 

Pros and Cons of an Above-Ground Storm Shelter

  • Pro: Easier to Install – If you don’t currently have a storm shelter, it’s much easier to put an above-ground model on your lawn since you don’t have to dig underground. 
  • Con: Shelter is Away From the House – As we mentioned, most people get hurt when trying to get into a shelter. Since these units can’t connect to the house, you’ll have to expose yourself and your family to potentially dangerous situations when heading to the shelter. 
  • Pro: No Blockage or Flooding Issues – With an underground shelter, you may have to worry about debris blocking the entrance (i.e., a fallen tree). This problem is much less common with an above-ground model. Also, these shelters are harder to flood, particularly from rain and runoff. 
  • Con: Exposure to High Winds and Debris – Currently, there’s no evidence to suggest that FEMA-rated above-ground shelters are less secure than underground models. However, if debris damages the shelter during a storm, you’ll have to repair it before the next tornado. Otherwise, you could put yourself and your family at risk. 

How to Build an Underground Storm Shelter

First of all, if your house has a basement, it’s much easier to convert your basement into an underground storm shelter. Since the infrastructure is already there, you don’t have to spend as much time or money installing a new shelter. 

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That said, if you don’t have a basement (or you can’t convert it), here are the steps to build an underground storm shelter. 

Step One: Hire a Ground Engineer

Before digging anywhere on your property, you need to consult a ground engineer. There could be cables, wiring, or sewage lines running underground, so you need to avoid any potential messes and repair bills. Also, a ground engineer can look at the type of soil you have on your property to determine the best spot for digging. For example, you may have soil that gets flooded easily, meaning water can seep into your storm shelter after it rains. 

Step Two: Choose Your Size

According to FEMA, storm shelters should have at least six square feet of space per person for a tornado shelter and 10 square feet for a hurricane shelter. So, if you have a family of four, you’ll need a unit that’s at least 24 by 24 feet and ideally six feet high. If you’re building in a hurricane-prone area, you’ll need a 40 x 40-foot shelter. 

Step Three: Choose Materials

When building an underground storm shelter, you can choose between four primary material types: 

  • Poured Reinforced Concrete – In this case, you’ll need to create a wooden frame to encase the concrete and place steel rebar pipes inside to reinforce it. Without the rebar, the concrete can crumble and collapse more easily. 
  • Reinforced Concrete Blocks – This option is much more efficient because you can buy the blocks pre-made. Also, it’s easy to do the math since you just have to calculate the number of blocks to buy. Then, you’ll use mortar to seal the blocks while you build. 
  • Welded Steel With a Fiberglass Coating – Concrete is porous, so water can seep in pretty easily. Welded steel doesn’t have that problem, but it’s much more expensive. You’ll also need to cover the interior with a fiberglass shield so that the inside of your shelter is more accommodating. 
  • Wood and Steel – If you’re building an underground storm shelter yourself, the easiest option is wood and steel. In this case, you create a steel frame and use wood to build the walls, floor, and ceiling. 

Step Four: Choose a Door

Realistically, you should have a solid steel door in front of your shelter. Since steel is so durable and resilient, you don’t have to worry about debris or other materials getting in during a storm. 

That said, the door will cost almost as much as the bunker itself, so you have to plan accordingly. Also, when installing the door, be sure to have it open inside so that you can’t get trapped if something falls in front of it.  

Step Five: Download a Building Guide From FEMA

If you’re going to build your own underground shelter, you need to ensure that it’s FEMA compliant. Otherwise, you won’t be able to claim any federal subsidies or grants. The building guide will have a layout and instructions on how to build with different materials. You can find the guide here

Bottom Line: Underground Storm Shelters are Ideal

Overall, underground storm shelters offer better protection, and if you’re starting from scratch, you can make the interior as accommodating as you like. However, you have to make the best choice considering your budget, location, and means. You might have to install an above-ground shelter in some cases because it’s not feasible to build one underground. 

FAQs About Underground Storm Shelters

How Much Does an Underground Storm Cellar Cost? 

On the low end, you can expect to pay around $2,500 for a prefabricated shelter. However, once you factor in the costs of digging and engineering, you can wind up spending over $30,000 in total

What is an Underground Tornado Shelter Called? 

There is no official name for an underground tornado shelter, but other common terms include a storm cellar or fallout shelter. 

Can You Survive a Tornado Underground? 

Yes, it’s very easy to survive a tornado underground. However, you may have to worry about flooding from rainwater or debris blocking your ventilation shaft. 

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1 thought on “Considerations for an Underground Storm Shelter”

  1. I have a tornado shelter already but I know the door is not the correct door that it has and I even believe that it’s done too straight and not very big at all that a tornado may even such us out of it. I was wanting to reconstruct if it will be cheaper for me. Do you have any recommendations for me?

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