Off-the-grid families, homesteading  Americans, and the prepper community have many things in common, one of which is the desire to live a self-reliance existence on a shoestring budget.
It is entirely possible to build a cheap, sturdy and earth-friendly cellar  that doubles as a storm shelter – without any extensive construction knowledge.
When building an earthen root cellar or storm shelter near your home, four important aspects must remain a top priority throughout the process.
First, the entryway must boast a door which seals completely to prevent as many spiders, snakes, squirrels and mice from taking up residence inside.
Second, the shelter must be designed large enough to accommodate not only significant stores of canned items, but must also possess enough open space that the family and any regular visitors can still fit inside when used as an emergency shelter.
Third, the interior temperature must remain at a constant 32 to 40 degrees and possess a humidity level of 85 to 95 percent. A dual gauge, made of plastic and available for a few books at most pet stores, can be affixed to a storage shelf to help monitor the environment inside of the root cellar. The cool temperature decreases the release of ethylene gas and thwarts the growth of microorganisms that cause decomposition. The humidity percentage will help prevent the loss of moisture through evaporation. A drainage pipe needs to be properly positioned and angled so that excess water drains away from the cellar, should any get inside.
Fourth, the structure should also be placed in a location that will remain out of direct sunlight so carrots, onions, apples and other produce don’t go bad. Some of the best spots for root cellars and storm shelters are along a soil bank about 10 to 20 yards from the home. If the family must run to the shelter during an emergency , it needs to be as close to the house as possible to enter and secure the door quickly. If a lot of time is spent inside a barn or workshop away from the house, consider building a secondary (or even third) shelter when it is economically feasible. Getting caught out in the field working the land or livestock could turn deadly very quick if the individual is forced to run multiple acres to reach a shelter.
The thickness of the walls will both help keep the interior of the structure cool and enhance the strength of the earthen building. If possible, take advantage of geothermal offerings and build at least the back, and if feasible, one side, of the shelter into a hillside. Stay away from areas near large trees, as the roots grow and the cellar walls could become cracked.
One of the most popular, sturdy, and low-cost ways to make a storm shelter and root cellar combo structure is to use a 1,500-gallon plastic stock tank or an unused septic tank. Such tanks are routinely stocked at agriculture retailers, and their stated use is for liquid holding, but they will work well for this type of project as well.
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Mother Earth News offered these tips about utilizing clean septic tanks in root cellars:
Most septic tanks have an internal partition that must be opened or removed to build from these root cellar plans. Try to find a tank without a partition, or ask your supplier to remove it before delivery. You can also punch through the partition yourself as part of the doorway-cutting process. Prices for new, undamaged 1,500-gallon tanks start at about $1,100, and 2,500-gallon models can be found for as low as $1,600. Discounts for damaged tanks may be as much as 50 percent.
Reinforce the area around the tank with wood 2X4 support posts and plywood to build a frame around the tank before covering the shelter with approximately 20 inches of soil on all but the door opening.
The root cellar  Mike Toppen built and was the focus of an article in Grit also included a pair of 2-inch diameter PVC vent tubes. The tubes helped to reduce the chances of mold growth while keeping the flow of fresh air into the root cellar. To increase the amount of air circulation inside the root cellar storm shelter combo structure, place food storage shelves about three inches away from the walls.
A perfect “hole-in-the-ground” root cellar is built in a good drainage area with sandy soil. Utilizing an elevated slope will move away any water that does accumulate inside the cellar. Be careful when digging the pit area in the middle of the cellar. Flare the sides so that the hole and ultimately the structure do not cave in.
Line the hole with straw or even dried leaves before putting the tank in so any excess moisture is absorbed and added humidity to reach the proper percentage can be reached. Wood chips are also often scattered about on the floor to increase humidity. If using the plastic tank and not just a wood or metal frame inside the earthen structure, the humidity ratio will likely be reached far more easily.
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As previously reported by Off The Grid News, papercrete  is sturdy, has many uses, and can be poured like traditional concrete. The Portland cement, water and paper products mixture is not load-bearing enough to support the layers of dirt without a post and beam frame. As long as a sturdy frame is constructed, papercrete blocks or poured walls covered by sod are also a reliable and inexpensive cellar option.
The door to the storm shelter  and root cellar structure needs to be comprised of extremely durable material and bolted to the stock tank frame. Iron and steel plates, even dinged ones you might happen across at a junkyard, would work well. Toppen had a rather ingenious idea when building his shelter; he bolted tires to the doorway. The stacks of tires on either side of the door added to the sturdiness of the root cellar and would help deflect debris during a storm.
Once the door is in place, firmly packing another layer of dirt around the structure will increase the geothermal attributes of the earthen building and once again, help protect it from flying objects during a tornado or hurricane.