Root Cellar Plans

These unique root cellar plans show you how to build a root cellar for food storage by adapting a new concrete septic tank.

| April/May 2014

The cool, moist and dark conditions of a root cellar make it the perfect place to keep many fruits and vegetables crisp and delicious for weeks — even months — of storage. And while there are myriad ways to store vegetables, our innovative root cellar plans show you how to build a root cellar by modifying a new, precast concrete septic tank. By following the plans, you'll cut an entrance, install a door, add a pair of vent pipes and cover the tank with soil to bring an old-fashioned, walk-in cellar into your modern life.

Choose a Concrete Septic Tank

You'll want to buy an unused septic tank for this root cellar design, but look for a deal to avoid paying full price. A percentage of all precast concrete septic tanks end up with small manufacturing defects that prohibit them from being used for sewage treatment. Suppliers sometimes offer discounts on these flawed tanks. As long as the tank is solid and sound, a chipped edge or a patchable hole won't prevent it from being a root cellar. You won’t need the plastic fittings or effluent filter found inside most septic tanks, so ask the supplier to remove these before delivery.

Tank size is another detail you'll need to consider when planning how to build a root cellar from a septic tank. The capacity of septic tanks is measured in gallons, with different models being taller or shorter. While you might be tempted to buy a 1,000- or 1,200-gallon tank because they’re common, you’ll get more food storage space and headroom with a tank that's 1,500 gallons or larger. Standard 1,500-gallon tanks typically measure about 5 1/2 feet wide by 5 1/2 feet tall by 10 feet long, while a 2,500-gallon tank provides more than 6 feet of interior headroom. Don’t choose a low-profile tank because it will be much too short to work in. 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.

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.

Best Sites for Root Cellars

The perfect location for a root cellar is nestled into an existing soil bank in a well-drained location 10 to 20 yards from your house. Ideally, the door should face north to keep out the sun’s heat. You’d be fortunate indeed to have all of these conditions, and most people have to modify their sites. Expect to pay from $50 to $100 per hour for a backhoe and operator to excavate your site for three or four hours.

Spread a 1-foot-deep bed of three-quarter-inch-diameter crushed stone beneath the excavated tank site and the planned entryway to support foot and wheelbarrow traffic. Crushed stone is easy to move around to make a level surface for your tank. Suppliers usually offer a delivery service using a boom truck to set down the tank wherever you want. Check the tank with a 48-inch level after the boom-truck driver has set it into place. If the tank isn't level, have the driver lift the tank so you can get a rake underneath to move the crushed stone. Keep setting, checking, adjusting and replacing the tank until it sits flat and level.

9/30/2017 9:22:31 PM

Is there any logic to placing tank 'upside down' so hatches could be used as drainage and ceiling would be much more sealed? Are tanks designed for structural integrity based on the 'right' side up? Just wondering.

9/30/2017 9:22:28 PM

Is there any logic to placing tank 'upside down' so hatches could be used as drainage and ceiling would be much more sealed? Are tanks designed for structural integrity based on the 'right' side up? Just wondering.

4/8/2016 10:16:18 AM

Hi, I have had a cellar for ten years. I live in Colorado as well as one of the others commenting. It did cost about 5,000.00 for concrete mine is 10x10x10. My father was a welder so once the floor, walls and stairwell was poured and set. He welded I,beam trusses. You can park a tank on top of it. LOL. The initial cost was great but having the upper door at ground level and the cellar door entrance at the cellar floor aided in keeping the cellar regulated. It did take two years for the concrete to adjust and stay constant in temperature.I can everything we eat probably 2500 jars a year, and store root veggies too. We did most of the work ourselves. It was well worth the effort. The entrance at ground level is facing west so I have a piece of board indulation mounted on in it. The walls inside have been insulated and I store canning pots and the large tamale steamer on a shelf above the cellar entrance. Hang chilies to dry, herbs too. It has payed for itself over and over. Never gets below 45 degrees in winter and never hotter than 57 degree in summer. I love it!

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