How to Build an Earthbag Bunker

Every single day we are bombarded by seemingly countless threats to our well-being by media and self-proclaimed experts.

a pile of earthbags

From catastrophic weather to increasing war and even the risk of nuclear war among major powers. There’s no doubt that the threat of catastrophe, be it natural or man-made, is very real and present in our lives.

One popular way to mitigate the risk of such disasters is to build a private bunker on your land. A bunker can be your safe place where you can weather the storm, literal or figurative.

There are many different ways to build a bunker, but most of them are highly involved in time, effort, and resources.

Face it; there is nothing about a bunker that is cheap, and for most of us the financials simply do not make sense. Furthermore, getting one installed in a truly discreet manner is a challenge unto itself.

However, there is a solution for at least two of these obstacles. Earthbag bunkers are one building solution that can provide you with some peace of mind in these uncertain times.

They’re relatively easy to build, far more affordable than other materials, and can provide you with a safe place to hunker down in case of an emergency. They are even a solution you can build yourself or with some help from family and friends.

In this article, I’ll tell you everything you need to know about earthbag construction and using it to build your own sturdy bunker. Grab your shovel and let’s get to it.

Our Earthbag House - How to buid a fortress on the cheap

What is Earthbag Construction?

Earthbag construction is a type of building that uses fabric bags filled with soil to create walls. The bags are then stacked on top of each other and held in place with barbed wire or another type of fencing material to prevent slippage.

The bags can be made from a variety of materials, but the most common are polypropylene and burlap.

To provide added support and stability, long or tall earthbag walls are usually reinforced with some type of metal, wood, or bamboo framing. Once the wall is completed, it is then usually plastered over with a mixture of cement, clay, and water.

This process creates a very strong and durable wall that is highly insulative and tough, while also resistant to fire, weathering, and pests.

Long used to provide strong and reliable structures quickly where other resources are unavailable, expensive, or not practical, the basic portability and flexibility of earthbag construction techniques have lent themselves to use in a variety of settings.

It has been used to build homes, schools, offices, storm shelters and of course, bunkers.

Completing the Stairs | Underground Earthbag Building | Weekly Peek Ep49

What is an Earthbag Bunker?

An earthbag bunker is exactly what it sounds like: a bunker built using earthbags.

Bunkers are typically underground structures, either partially or fully, that are designed to provide protection for occupants in the event of a disaster or other threats.

Properly designed, sited, and built they can be used to protect against weather events, such as hurricanes, tornadoes, and floods.

They can also provide safety from man-made disasters, gunfire, and even chemical or nuclear threats if specially equipped.

While bunkers have been used for military purposes for centuries, the modern-day bunker has evolved to be more of a private safe room or panic room designed to provide safety for families and individuals in case of emergency.

This type of bunker is typically built into a home near it and can be used as a dependable shelter in the event of any of the aforementioned disasters.

For preppers, having a personal bunker for any occasion is seen as something of a “bucket list” prep owing to their cost and complexity.

Advantages of Earthbag Bunkers Over Other Types

Compared to traditional construction methods, and particularly for bunker building, earthbag construction has many advantages.

The most obvious advantage is the cost. When you factor in the price of land, permits, frameworks, and other necessary materials, building a traditional bunker can cost upwards of $30,000.

An earthbag bunker can be built for a tiny fraction of that price since dirt and the bags to hold it are quite cheap or even free.

Wood for framing and barbed wire are also inexpensive, considering the limited quantities required for a typical bunker.

Another big advantage is its portability. Unlike concrete or steel bunkers which require heavy, expensive materials to be transported to the site, earthbag bunkers can be built almost anywhere using only a few simple tools and soil taken from the site itself, or obtained nearby.

This is perfect for those who want to build a bunker on their land but do not have transport or money available for the materials required for other types of construction.

The flexibility and portability of earthbag construction also make it ideal for building in difficult or remote locations.

If you own land in a rural area or somewhere with difficult terrain, earthbag construction may be the only practical way to build a bunker there.

It might be slow going, but if you can get men, basic tools, and some light, easily transported materials to the location you can get your bunker installed.

Another big advantage of earthbag construction is its durability. Earthbag walls are incredibly strong and can resist high winds, heavy rains, fire, and potentially even earthquakes better than many types of traditional construction.

The bags themselves are usually made from a very tough fabric that can withstand a lot of wear and tear, and the wall as a whole is very stable since it is essentially one big mass of soil.

Once framed and finished, they are comfortable and weatherproof inside, meaning that your bunker can be used for long-term habitation if necessary.

Building Your Earthbag Bunker Step by Step

The following section will give you a step-by-step guide for building an earthbag bunker. Keep in mind, that your precise process may well change depending exactly on the design and layout.

But not to worry, these steps have been refined by experts in the field and you can depend on them, just make sure to do your own diligence when it comes to planning and execution!

Determine Purpose

The first thing you’ll need to do is determine the purpose of your bunker. Are you building it to protect against nuclear fallout?

Then you’ll need a very different design than if you’re just looking for a storm shelter or “bolt hole” in the woods.

Some folks just want a super strong and weatherproof root cellar or store room. That’s okay too.

Decide on the size, shape, and layout of your bunker based on its intended purpose.

  • How many people are going to be with you?
  • How much gear do you have to store?
  • How long do you plan on being there?

All of these factors will play into the final design.

A thorough discussion of all of these factors in context is a bit beyond what this article intends to do, but you can find lots of plans and other resources with a search on the web, and be sure to check out the resources section below for more.

Siting

Siting is choosing the location and actual orientation of your bunker. You want to make sure you have a few things squared away before you start digging.

First, make sure the location is actually on your land. This seems like common sense, but you’d be surprised how many people build structures on or encroach upon their neighbor’s property without realizing it.

In some cases, the neighbor might not care, but in others, they could take legal action to have the structure removed. Ouch!

To avoid any potential problems it’s always best to err on the side of caution and have a survey done if you have any doubt whatsoever.

Next, consider the terrain’s effects on the bunker itself. Can you take advantage of a hillside or other existing feature to aid in construction or camouflage the bunker?

Conversely, is the land too steep or rocky to make excavation feasible without expensive equipment or a lot of extra work?

You’ll also want to make sure that the site chosen is not in an area prone to flooding. Depressions, dips, and valleys are notoriously bad for this.

This can be difficult to determine if you’re not familiar with the area, but again, a surveyor can help. If you’re really unsure, it’s best to build on higher, well-drained ground just to be safe.

Once you’ve decided on the perfect location and orientation, double-check your plan against the site for space and accessibility, and then it’s time to start excavating!

Excavation

The first step in any construction project is excavation, and building an earthbag bunker is no different. The only real difference is what you do with all that dirt once you’ve dug it up!

Assuming you’ve chosen a site that is large enough and not too steep, the excavation process is actually quite simple.

All you need, at the bare minimum, is a shovel and some elbow grease. A lot of elbow grease, actually!

This is a phase where you’ll want to bring in as much manpower as you can or some earthmoving equipment if you can afford it.

Start by clearing away any vegetation from the building site. This will not only give you a clean canvas to work with, but will also help to prevent unwanted plants and roots from damaging your structure later on. Once the area is cleared, start digging!

How deep you need to dig depends on the height of your bunker walls and the soil conditions in your area, but as a general rule you’ll want to excavate to a depth of at least one-half the height of your finished walls (for a semi-subterranean bunker).

So, if you’re planning on building walls that are 7 feet high on a partially below-ground bunker, you’ll want to excavate down 3 to 4 feet, allowing a bit extra for foundation and flooring.

This may seem like a lot, but there any worthwhile earthbag bunker is going to be at least partially underground for strength.

The density of the soil walls (in the bags) backed up by the surrounding soil of the earth will be proof against nearly any disaster save a direct bomb blast or earthquake.

How to keep moisture or water away from your earthbag foundation and walls

Foundation and Drainage

This is a critical component of an earthbag bunker that most first-time builders omit or mess up.

A foundation is necessary to evenly distribute the weight of your walls and roof, as well as provide a solid base to build upon.

Without a proper foundation, your bunker is likely to collapse or settle unevenly, especially if you live in an area with high clay content soils that expand and contract with changes in moisture.

Drainage is also important to prevent water from pooling around or underneath your bunker and causing problems.

A small French drain (a ditch with gravel and perforated pipe) dug around the perimeter of your bunker and leading away from the structure can easily help to keep water at bay.

In most cases, a simple gravel or stone foundation set on well-tamped earth will suffice.

If you’re unsure about your soil conditions or want to ensure a reliable foundation, it’s not a bad idea to pour a concrete footing for extra strength assuming the footprint is small enough and you can afford it.

How we fill sandbags aka earthbags

Fill Bags

Time for the next “funniest” part of building the bunker: filling the bags with soil! This is another part you’ll definitely want help on, and preferably a 3-man team at the least, though you can do this yourself in a pinch.

The two most important parts of filling your bags with soil are the soil quality and the fill amount. This is a surprisingly precise operation on both counts.

The soil you use needs to ideally be moist subsoil that has some clay (so it will tamp solidly and reliably), and the bags should only be filled appx. 2/3 full so they can deform and fill gaps solidly in each course of the walls.

Consistency is a virtue here, so your filler team needs to use buckets, coffee cans, or other units for measuring out the fill load of each bag with reliability.

You want the same volume of dirt and the same quality of dirt in every bag. This will prevent problems down the road. Close the bags with clips, wire ties, or any other method.

You have a choice on how to proceed here: you can either have your layer man place the bags at the building site as they’re filled or you can batch the bags and then lay a course or section in one go. Do what works best for you and your team.

Lay Wall Course

Time to build the walls of the bunker, or rather the first row of the walls of your bunker. Lay the bags in place according to your plan, and pay attention to keeping them snugly and evenly touching each other. Gaps will cause problems.

Compact the Course

Once you have your course in place, it’s time to compact the bags. This is a vital step because even small air pockets in the walls will cause instability, making them weaker and more vulnerable to collapse.

The simplest way is by using a manual tamper bar, with heavier ones working better. Generally, you won’t need anything heavier than a 1-lb tamper bar and 1/2 or 1/4-lb versions can still work well enough.

Take care to tamp each bag thoroughly but even once the course is in place, be mindful to keep them level and even. Check for level before moving on.

Lay Wire on Courses

With your first course or courses in place, it is time to lay on barbed wire to prepare for the next course of bags. Don’t worry; this isn’t some crazy and overtly militaristic defensive measure.

The barbed wire serves to further strengthen the walls by helping the bags bond with each other and preventing slippage.

Ideally, you want to use 2 strands of 14-gauge barbed wire for this, though 12-gauge can work in a pinch if that’s all you have on hand. Simply unroll it on top of the course, being mindful to keep it straight and parallel as best you can.

In the end, it should look like a set of railroad tracks running down the center of the courses. Use wire stays, bricks or rocks to hold the wire in place until you are ready for laying the next course.

You can leave wire stays or staples in place if they are flush with the surface of the bags, but rocks and bricks should be removed as you lay the next course of bags on top.

Place Next Course

Now, repeat the previous steps as necessary according to your plan to complete the walls of the bunker. This is where offsetting the bags becomes necessary. This is much like the offset of bricks in conventional masonry.

Usually offsetting is done at intervals of half the length of a bag, but alternate offsets may be called for depending on your plan.

As you lay each course, check the level and plumb regularly to ensure that your walls are staying true. Failing to do this can prove disastrous, especially with curved or domed walls.

Once the walls are built up to the desired height, it’s time to install framing, if necessary, and then complete the roof.

Add Framing as Necessary

Walls that are longer than 8 feet will require some form of framing to provide reinforcement and support the weight of the roof.

This is generally done using 2x4s placed at intervals no greater than 4 feet on center across the uppermost course of bags, with longer spans requiring additional supports.

Internal reinforcement of placed walls can be done with driven rebar. You want to create a frame that is strong enough to support the weight of the roof while also being level and plumb.

Now is also the time to finish out the frame for the door or hatch of the bunker. This can be done using 2x4s or 2x6s placed around the perimeter of the opening, with the frame being flush with the surface of the bags.

Roundhouse Part 11, building a round wooden roof. Earthbag, man cave, tiny home

Complete the Roof

The roof of your bunker is essential not just for shelter and protection, but also for supporting the weight of the ground cover if you are using it.

The roof can be made from plywood or other materials (and roof designs) if above ground, or the earthbags themselves if you are going for a dome or igloo-type bunker.

If using plywood, you will want to use at least 3/4-inch plywood, with 1-inch being even better.

Cut the pieces to fit snugly over the frame of the bunker, being mindful to allow for overhangs if desired in a partially-underground bunker. Secure the plywood to the framing members using screws or nails placed every 6 inches.

Cover and/or Backfill

Now, with the structure of your bunker complete all that is left to do is fill in the area around the walls with soil and cover the roof likewise, if going for the completely underground approach.

Start by shoveling in the soil around the base of the walls evenly around the perimeter until it is level with the bags. This will help to further support and strengthen the walls.

For a fully underground bunker, you can simply cover the roof with soil or place an additional course of bags over top for added overhead protection.

If going for a partially above-ground structure, you now need only add a roof of your choice. This can be anything from a wood trussed roof to metal or even shingled roof.

Finish and Equip

Your bunker is complete, but it needs finishing touches. Depending on your purposes and requirements you might need to install ventilation, lighting, and/or other amenities.

Now is the time to plaster the inside walls if you desire, though more spartan preppers leave them bare with no ill effects.

Remember to use lime or soil plaster to ensure adequate breathability; cement plaster is inadequate!

Shelving and bedding could be needed as a contingency shelter. Consider too the notion of camouflaging your bunker, especially if you are intending it to be a secret fallback point in case of war or massive civil unrest.

This can be done with live vegetation and other line-of-sight blocking obstacles, or accomplished through the use of camo netting and other techniques.

An underground bunker with a natural soil roof and carefully concealed entrance is virtually undetectable to the naked eye so long as evidence of human activity and passage is managed.

Here, the sky is the limit, and the final equipment of your bunker is limited only by your budget and effort.

Build a Sturdy Bunker Cheap with Earthbags

There are many ways to build a bunker, but earthbag construction is one of the most affordable and effective methods for everyday preppers.

With a little planning and effort, you can build a bunker that will serve your needs for years to come.

Whether you can build a small, simple tornado shelter or a more elaborate complex designed to withstand just about anything, an earthbag bunker can do the job.

Frequently Asked Questions

Below are some of the most commonly asked questions about earthbag bunker construction and bunker theory in general.

How long does it take to build an earthbag bunker?

The length of time it takes to build an earthbag bunker depends on the size and complexity of the design as well as the number of people working on the project.

A small, simple bunker can be built in a matter of days by a couple of people working diligently.

Larger, more complex bunkers will obviously take longer, with some projects taking weeks or even months to complete.

How much does it cost to build an earthbag bunker?

The cost of building an earthbag bunker likewise varies, but when considering the cost of raw materials like the bags, barbed wire, plaster, framing materials, fasteners, and the like (everything except the dirt, labor, and tools) you can easily build a bunker for under $350 depending on market rates.

Keep in mind, that the rental of heavy equipment or hiring of labor will greatly increase costs, though it could save you a ton of time, too.

How can I keep my bunker from flooding?

The best way to keep your earthbag bunker from flooding is to build it above the floodplain if at all possible.

If this is not an option, then you will need to take extra care to properly seal and waterproof the walls and roof. Expanding your French drains is a good idea as is using larger drain pipes.

Heavy, thick mylar sheeting can be used to encapsulate the exterior walls prior to backfilling, too.

Can I really build an earthbag bunker on my own?

You certainly can, but depending on the size and complexity of your design it might be one heck of a task, and not for the weak. Consider it wise to enlist the help of a few extra sets of hands, especially if you have no prior experience with earthbag construction.

Are there any other considerations I need to take into account?

When building your earthbag bunker, be sure to take into consideration the needs of those who will be using it. If you are bugging in with your family, then make sure the design is comfortable and reasonably livable.

If you are building a bunker to be used as a long-term survival shelter, then make sure the design includes room for all of the amenities you will need to survive for an extended period of time.

Additional Resources

Two excellent resources are here for any would-e bunker builders:

earthbag bunker pinterest

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