How To Build An Underground Bunker (In Just 8 Steps)

If you've ever wondered how to build an underground bunker you're in the right place...

I probably don't need to tell you that a bunker is typically a defensive military fortification, usually built underground, to protect people and their valuables from falling bombs or other threats. 

Or that bunkers became popular during the Cold War, however, the current coronavirus pandemic has seen bunkers soar in popularity again. 

But you may be thinking you just can't afford to build an underground bunker or that it's not possible.

And sure; while you may not be able to afford to have a swanky luxury bunker installed with all the mod-cons, you can instead build your own basic bunker in preparation for whatever curveball comes next.  

Keep reading to find out how to build an underground bunker in just 8 steps

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How To Build An Underground Bunker

Step 1: Get your permits

Building an underground bunker isn’t as simple as just digging up a patch of land. 

Permits need to be obtained to ensure the safety of yourself and everyone else involved. 

Failure to comply with permits may cost you in the long run - both in terms of money, and safety. 

To obtain your permits, you should contact your local building department with a basic layout of what you hope to build. 

Regardless of your location, you must call 811 before you start digging to ensure you don’t accidentally hit an underground utility line. 

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Step 2: Choose a location 

Once you’ve acquired the necessary permits, you can start considering where your bunker will be located. 

Avoid areas close to large bodies of water as you run the risk of flooding, 

and you should avoid areas surrounded by trees and vegetation as you’ll have to cut through tree webs, which is both difficult and environmentally damaging. 

Like we mentioned above, you need to steer clear of utility lines.

You should avoid digging 18-24” on all sides of the line and if this isn’t possible, it’s an indication that you need to find a new location for your bunker. 

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Step 3: Develop a blueprint 

After you’ve chosen your location, you can measure the area so you know exactly what you have to work with. 

FEMA recommends allowing 5-10 feet per person to avoid claustrophobia, and you can also maximize the space by combining certain areas (kitchen and living space), building storage spaces vertically rather than horizontally, and installing wall-mounted furniture, for example, a folding table or desk. 

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Step 4: Choose and purchase your materials 

Your bunker should be made of strong, durable materials that can endure the elements.

Metal sheeting, bricks, and concrete are the most popular materials. These are all sturdy and weather-resistant, however, metal tends to be slightly more expensive

Reinforced concrete is best for strength and durability, while self-healing concrete reduces maintenance requirements and has a 200-year lifespan.

So, what materials shouldn’t you use?

Avoid wood, as it’s not weatherproof and is prone to rot and infestation. Wood is fine to use inside your bunker, as long as you maintain the upkeep.

Shipping container bunkers are a spacious and cost-effective option, but you’re more restricted when it comes to customizing your layout.   

If you use a shipping container you will also need to reinforce it, as shipping containers aren’t built to be buried.

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Step 5: Select your tools 

As you might have guessed, using a shovel alone to dig up the land is going to take a very long time - and a lot of effort.

You’ll start by marking out your perimeter, then using a trencher to mark the outline, and an excavator to dig up the earth.

A mini excavator is ideal for tight or awkward digs where there isn’t much space, such as a backyard.  

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Step 6: Purchase living essentials 

Your underground bunker is not going to be much use if you don’t have it kitted out with all the essential living materials (also consider where and how you build it as your bunker can flood if the entrance is not built  correctly)

There are five key materials you’re going to want to acquire at this point: 

  1. Ventilation and Air FiltersThese help keep your bunker ventilated. N.B.C. (Nuclear, Biological, Chemical) filters are the best types for protecting against air contaminants and promoting air circulation. 

  2. GeneratorThis will be your source of electricity. You can determine the size of the generator you’ll need by calculating the combined wattage of all the electrical items you intend to use in the bunker. 

  3. Water Filters: This will keep your water clean. For an underground bunker, a UV filter is ideal as these use UV light to rid the water of viruses and bacteria.

  4. Waste Removal System: You must have a well-managed waste system for your bunker. There are a few different options, including a simple room with a trench, PVC piping, a compost toilet, and a wastewater pump and lift system. 

Read more about these options and their benefits and drawbacks, here

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Step 7: Start digging!

Once you’ve got a clear plan of your bunker, the essential living materials you’ll be installing, and the materials you’ll be using to build the structure, you can finally start digging. 

However, to prevent cave-ins, there are a few protective systems you need to consider utilizing when you dig your trench: 

  1. Sloping involves cutting the trench wall at an angle to create a slope.
  2. Shoring requires building a support system to keep the dirt in place and prevent it from collapsing. 
  3. A trench shield, also known as a trench box, protects the person inside in the case of a cave-in. This should be used in conjunction with the other two systems, as it will not prevent a cave-in from happening. 
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Step 8: Build and reinforce your shelter

Reinforcing your shelter will ensure it can withstand the weight of the land above it.

A sturdy foundation is also essential and reinforced or self-healing concrete will be the most durable material for this.  

Metal beams across the trench can prevent collapse, while an extra layer of reinforced concrete on the outer walls of the bunker will provide added protection. 

The bunkers’ walls should be at least 1-3 feet thick, and if you’re using metal, strengthen this by adding a layer of brick or concrete inside.

If you’re using concrete alone, ensure it’s thick and reinforced.

It’s a good idea to reduce the risk of water damage and mold by coating your bunker and protective systems with waterproof materials such as rubberized asphalt or cementitious waterproof coating.

If you’re building your bunker in an area prone to earthquakes, you’ll need to pay even more attention to reinforcement methods.

And make use of earthquake-proof materials like shear walls, cross braces, and moment-resisting frames that can redistribute the seismic forces and protect the bunker from collapsing. 

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And That's How To Build An Underground Bunker In 8 Steps

We hope this article has been helpful and has informed you of everything you need to know about planning, and building, an underground bunker. 

Now, while you’re waiting for your permits to come through, why not start stocking up on canned goods and bottled water?!

Last update on 2023-09-28 / Affiliate links / Images from Amazon Product Advertising API