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How Deep Should An Underground Bunker Be?

Photo collage of different Underground Bunker.

Picture the scene, you wake up from a loud thud and know something is wrong. You wake up the whole house and try to make sense of it, and that is when you see it: Aunt Gertrude is a zombie, she’s trying to get in and you know you have to run! But run where?

Time is ticking and then you hear the tornado siren. It’s chaos; now have Aunt Gertrude who is already wondering if prune juice will go good with brains and a tornado that’s tearing its way through the town and on its way to your house. That was when I woke up and I knew it was time to invest in an underground bunker.

There is a lot of debate around this topic. Most experts say to withstand nuclear blasts, bombs, natural disasters, and radiation; you need to build a bunker at least 10 ft deep. This is not the only factor that will determine the depth. Factors like material and state regulations do play a role.

After a slightly awkward call to Aunt Gertrude, I have confirmed that she is not a zombie and does not intend to become one in the near future. What a relief, but that still made me wonder about things like bombs, nuclear blasts, not to mention wars and natural disasters. I was curious and decided to learn more and answer the question; how deep should an underground bunker be? 

What is an Underground Bunker?

This is the entrance to an underground cellar with wooden doors.

An underground bunker sometimes called a bomb shelter or fallout shelter is a structure that is built underground for emergency situations. These bunkers are found all over the world and can be a literal lifesaver in times of emergency. It is like a panic room but bigger and underground.

These bunkers can come in all varieties, shapes, and sizes. Some are made from concrete, some are old shipping containers and some people have converted their basements into underground bunkers. Some are found in former military areas, leftover from the cold war.

An underground bunker might sound like an underground tree fort but some of these bunkers can be rather elaborate and house a lot of people. Now the ones you build for yourself and your family might not house a town but as long as it has the essentials, you will have a safe place to go to when an emergency situation hits.

How Deep Should an Underground Bunker Be?

A close look at an underground bunker spiral staircase.

Now that we have established what an underground bunker is, we can go into more detail on how deep they should be what material they can and should be built out of, and the regulations that are in place that can interfere with your plans to build a bunker.

Designing and Constructing the Bunker

There are some considerations to take into account when you have decided to build an underground bunker. You have a few options to choose from:

  • Build it yourself
  • Buy a container and renovate it as an underground bunker
  • Hire a company that specializes in building underground bunkers

DIY Underground Bunker

This is an underground storm cellar with wide open doors.

Now when building the bunker yourself, you will have to do a lot of research, and though you might be able to do it cheaper, this might end up being a money pit if not done correctly. This is also a big factor in the depth of your bunker. Some of the factors to keep in mind with a DIY underground bunker are:

  • Digging Equipment, can be costly
  • The type of material you want to use to build your bunker
  • The regulations of the state you’re in, you might need a permit or building plans
  • The size of your property, if you have big land it will be easier to build under open land than under a yard in the city

Buy a Container and Renovate It as an Underground Bunker

Buying a container and renovating it to use as an underground bunker is a very budget-friendly option but there are drawbacks. The first one is that they are made of steel and will only last about 15 years underground without maintenance due to the moisture and acidity in the earth. The second one is that they can’t be buried too deep underground as the weight of the soil on top will buckle the roof.

It is especially true as time goes on and it starts to erode. You can coat the structure in various sealants but this is only a temporary solution. Covering the sides with gravel and concrete will be a better option but not on top.

You would also need to put extra braces in to strengthen the inside and reduce the chances of the roof caving in. Lastly, they need to be maintained properly. This can get costly.

A container also needs to be thoroughly cleaned and have the paint removed on the inside as it is toxic, especially underground.

Hire a Company That Specializes in Underground Bunkers

This is a partisan underground bunker with mosaic stone walls and wooden support.

This would be a better if more expensive option. Contractors that specialize in underground shelters have all the equipment needed to construct and install the bunker. They will also be able to place the bunker deeper for added protection.

They use the best materials for underground use which means the bunker will last for a very long time. They also install all the needed extras such as:

  • An air ventilation system, you need this in order to breathe underground and filter out any toxins such as radiation or biological material
  • Sanitation and waste disposal system that needs minimal maintenance as you might be stuck underground for days or weeks in an emergency situation
  • They can install generators and solar panels to provide power and heat

Regulations and Laws

This is the old underground fort of Grodzisko under a hill.

So do you need a permit to build an underground bunker? The short answer is yes you do. It might sound silly because it is under your own yard or land but the reason for this is that there might be water pipes, underground gas pockets, electric pipes, or old buried things like a mine that might cave in.

These regulations are there for protection. It might also interfere with how deep you can put your bunker. This might be a bigger problem if you are in the city.

Tips To Help Choose the Depth of Your Bunker

This is an underground bunker entrance with stairs and concrete blocks at a wooded area.

If you are really up to building a bunker here are some tips that might help you:

  • Try to build out of town, there will be less to worry about when it comes to regulations and you might be able to situate the bunker deeper.
  • The deeper the bunker is, the safer you are, especially from nuclear blasts. Some blasts can penetrate as deep as 1000ft.
  • Use concrete if you are building your own bunker, this is by far the strongest and sturdiest material to build with and with proper support it can take the added weight of the soil if you build deeper. It is also maintenance free and does not corrode.
  • Build in a honeycomb design, the hexagon shapes helps with load bearing and uses all available spaces but less material to build. It also makes for a sturdier structure.


It is a great idea to be prepared for the future because, in the current state of the world, we might have needed an underground bunker sooner than we think. In the past, a lot of people thought it was downright hilarious and paranoid to want an underground bunker or shelter but I think in the last year they have come to realize, anything might happen. It is a daunting but exciting project to take on and might be expensive, but when your life and that of your family are in danger, you will be happy you made the choice.

As for me, I’ll be keeping a very close eye on Auntie Gertrude from now on.