How To Build A Root Cellar

Build the Ultimate Root Cellar | 9 Steps to Self-Sufficient Food Storage

October 05, 2020

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Root cellars are cool old tech that keeps food — primarily fruit and vegetables — fresh for up to a year, without any electricity. Building a root cellar is great way to store harvests from large gardens, and as a backup in case of emergency. So here is my simple guide on how to build root cellar, with bonus tips at the end —

Choose the Correct Site

The first and most important step when building a root cellar is choosing the right place to put it. The best spot for a root cellar is on a north facing hillside with good drainage.

Not ever site has access to such a hillside, or that location may be too far from the home to make it practical. Here are the factors you want to consider, most important first

  1. Has good drainage (ei isn’t a pool of water when you dig)
  2. Is near the home or place of use
  3. On a hillside
  4. On a north facing or shady slope

Drainage

Drainage is by far the most important, because a root cellar built in a location that naturally pools water will become a disaster very quickly.

One way to test drainage in a site is to dig a hole about as deep as the root cellar will be. If it immediately fills with water, find a new site. Also, check the hole after a rainstorm, and see if the water was able to drain off, or if it stayed in the hole.

Locations with small amount of water in the bottom may be able to be salvaged by using a sump pump to remove small amounts of water.

Location

Root cellars should be relatively close to the home, and preferably the garden. However, they do not need to be under or right next to the home unless that’s your best option.

Ideally, root cellars should only be accessed occasionally, maybe a few times a week. Opening the door too much will affect the climate, and may make your food storage go bad early.

So, moving a root cellar far enough from the house to discourage recessive visitation might be a good system design. In permaculture, root cellars would probably be best placed in zones 0 or 1.

Hillsides

In general hillsides are good, locations for root cellars because the reduce the amount of digging you need to do, make getting in and of the root cellar more convent, since you won’t need stairs or a ladder.

North facing slopes (or south facing for those in the Southern Hemisphere) are naturally cooler, with less potential for sun to shine in the cellar door, potentially causing root vegetables to start growing. North facing slopes were preferred historically, when most people had a root cellar.

Plan How Much Space You Need

Choosing the right size for a root cellar is important to making it a success. Too small and you will have difficulty getting to what you need. But too large and you significantly overspend on time and materials. And, potentially reduce it’s temperature stability. The biggest mistake people make when building a root cellar, is that they make it too big.

Even a 5’ by 8’ root cellar is enough to hold up to 30 bushels of produce. Plenty of room for most families.

Overall, the size of the cellar you need depends on how much you plan to harvest from your garden.

For more information on building a root cellar and storing food, check out the Root Cellaring book, which is the best reference on the topic.

Dig Out The Rough Hole

With the planning done, it’s time to begin construction. Begin by digging out a hole 1’ – 2’ larger than the outer dimensions of you walls in both dimensions, and open to the sky. You will need the ceiling portion clear to build the roof.

The depth of the whole depends on how cold your winters are. The bottom of the root cellar must at least be below the frost line in your climate.

National Weather Service Frost Depth Map

Beyond that, you have the option of digging down further, or not. Digging a shallower holes means that you can will have part of the cellar above ground, creating an earth berm root cellar. You can also go all the way down to where the top of the ceiling is at least the frost depth below ground produces traditional root cellar.

Keep some of the dirt near by to fill back in around the walls and cover the roof. With earth berm style cellars, you will probably need all of the dirt, or even more to cover up the cellar again. Traditional cellars probably will have extra dirt.

Build Up the Walls

Next, you will be building the walls. There are a huge number of ways to do this. Mother Earth News recommends buying a concrete septic tank and just dropping it in the hole.

Other options for building a root cellar include —

  • Cinder block walls
  • Earth bag
  • Log cabin style
  • Poured concrete
  • Septic tank

There are surely many more methods possible. And, you should choose one that suits your own skill set the best. However, it is important that the walls you build be able to pass moisture, and survive direct ground contact.

If you don’t have building skills already, then one of the easiest and almost certainly the cheapest methods is the earth bag building style.

Earth bag building requires sand bags, barbed wire, and dirt.

  1. Fill each bag as full as possible with dirt, and tie off
  2. As you fill them lay them down one row at a time like bricks
  3. Tamp each row down hard with a hand tamper
  4. Say two strings of barbed wire along the wall between each layer to prevent the bags sliding
  5. Continue up using a level to make sure the wall is perfectly plump (straight up and down)

Back Fill and Mound Up

With the walls in place, back fill the dirt around the outside of the walls and then pile up the dirt against above ground wall segments up to the roof line, as necessary.

If you are on a slope, you may want to use a more modern method to prevent water egress from the walls. Instead of dirt, place a plastic drain pipe around the base of the walls, sloped down with the outlet on the downhill side. Fill the area between the walls and undug earth with gravel until about 1’ from the surface or top of the wall, whichever comes first. Then fill and mound with dirt as before.

Ready the Floor

Traditional root cellars are earth, with no covering. In order to be ready for shelving, use a shovel to level out the floor. Walk over the floor and tamp it with a hand or gas powered tamper / jumping jack. If you have heavy machinery or a tractor that can access the cellar floor, you might drive it over as well.

As the cellar is used and compacted by foot traffic, the floor will harden. Eventually, it will get so hard that you will even be to sweep the floor clean.

There are also other options including building raised flooring out of wood or store. And, natural builders also have invented more complex methods of earth floors building that produces a nicer looking end product by building up the floor with multiple layers and sealing with linseed oil. However, these methods are not necessary to produce a functioning root cellar.

Install the Ceiling

The ceiling will be supporting a thick layer of dirt, and needs to be very strong. Again, the method you use depends on your skills, and will probably be similar to how you made the walls.

Traditional builders often layer out multiple logs across the walls, covering the entire space, and used that is a roof.

More modern possibilities include timber framed ceiling with pressure treated wood and a layer of plastic on top; or the ubiquitous poured concrete (a project best left up to skilled individuals or professionals).

If you went for the septic tank idea, then you already have a roof.

Earth bag builders can use a framed wood roof, or go with the slightly more ambitious domed earth bag ceiling.

Building a domed earth bag ceiling requires that you first build a domed wooden support of the same shape, and then build up the courses one by one toward the center. Once the final “key stone” earth bag tamped an in place, the structure will be self supporting, and the wood supports can be removed.

Provide a Door and Ventilation

If your root cellar is built in to the side of a hill, then your door can be a typical house door. While wooden doors might work, metal or vinyl doors will generally last longer and seal better in the damp conditions.

Root cellars build on flat land will need a hatch and stairs or a ladder. The hatch will probably need to be custom made, and can be wood or plastic on top with a good layer of insulation. Hatches need to seal well to prevent surface water from flowing in to the cellar below.

Root Cellar Ventilation

Cellars need adequate ventilation to prevent build up of gasses produced by decomposition. When these gasses build up, they speed up the rate at which food spoils, hence the old adage, “one bad apple spoils the bunch.”

Typically this is accomplished by two 4" pipes run through the ceiling and out to the air at opposite ends of the cellar. One of the pipes should extend to near the floor, while the other will end near the ceiling. This height difference will encourage natural convective air flow.

The outside ends of the pipe need to be protected from the rain using a vent covers, or by putting a ‘L’ shaped segment on the ends. You will also want a fine wire mesh or window screen well attached to the outer end of the pipes, to prevent small animals and insects from entering and plundering your stores.

Build Shelving and Storage Containers

Lastly, you will want to build or install shelving, and bring in proper storage containers.

Root Cellar Shelving

Strong shelves can built using construction lumber and plywood. Although, discounted metal shelving at home improvement stores and places like Costco can be even cheaper than building them yourselves with wood.

Narrow metal feet on earth floors should be supported with small flat stones or tiles underneath, to spread out the lead and prevent the leg from digging in. This also prevents direct earth contact, which will increase the life of your shelving.

Take care that shelves are installed perfectly level on solid ground, to prevent accidental tipping. In earth quake zones, you may want to attach the top of shelving to the wall. Check with local authorities to see what they recommend.

Bungees rope across the exposed edges of the shelf also help prevent items from accidentally slipping off

Root Cellar Storage

Fruits and vegetables in root cellar storage need to be place in proper containers in order to prevent early rotting. What type of storage depends on what type of vegetables.

Larger pumpkins and gourds can usually just be placed directly on the shelves.

Apples are traditionally stored in wooden boxes with loosely slatted sides, to allow airflow. Although, cardboard boxes with air holes also probably work as well.

Plastic totes may work alright with some modifications. And, are probably best used for storing potatoes in dirt.

For more information on building a root cellar and storing food, check out the Root Cellaring book, which is the best reference on the topic.


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