How to Build a Root Cellar

Although we may can or freeze many items, a root cellar provides a place for long-term storage of bulky produce such as apples, onions, potatoes, carrots and squash. If you need a squash, apples, carrots or potatoes, just open the cellar door and help yourself. Building a root cellar is a satisfying project for the do-it-yourself homeowner, as the cost of materials is low and the cellar will last for decades. A root cellar will save money for many years to come, yet if you construct the cellar yourself, the cost of building materials is less than a family would spend in one winter buying produce at supermarket prices.

Planning & Preparation

1. Determine the amount of produce and product you are likely to store. An 8-by-12 foot cellar is adequate for most families. In addition to being a storage space for produce, a root cellar also provides security and shelter in the face of a storm or disaster. When determining the size, consider the amount of safe space your family may require. A well-constructed root cellar will provide above-freezing temperatures of moderately humid circulating air.

2. Sketch out a plan for your root cellar. A root cellar with a dirt floor takes advantage of the natural cool humidity of the earth, and a floor frame is not required.

3. Choose the right location. The ideal site for a root cellar is on a slope or hillside away from the prevailing winds. If a hill or slope is not available, choose the highest ground available to provide adequate drainage. Pick a convenient spot. Remember that during the summer harvest and all through the worst of winter weather, you will visit the cellar frequently.

Basic Root Cellar Construction

1. Excavate a hole 16 feet long by 12 feet wide by 4 feet deep if you are building an 8-by-12 foot cellar. Use a No. 10 shovel, a pick and wheelbarrow or hire the services of a excavation contractor to dig the cellar space. Dig the entrance ramp 4 feet wide and sloping downward for 6 feet, 2 inches to the bottom. Make the floor as level as possible. (Note: A portion of the cellar will be below the frost line in the ground; the side walls and roof will also be covered with an insulating layer of soil. The height you build the walls will determine the height of the cellar. Most cellars are constructed 11 concrete blocks high to provide an 8-foot ceiling.)

2. Stake out and measure within the bottom of the hole. Begin 32 inches from the entrance. Pound stakes in the ground to designate an area 6 feet, 8 inches wide by 10 feet long. Place the stakes an equal distance from the sidewalls. Make sure the area is square. To mark the footing trench, pound four more stakes 18 inches outside the marked area. (The footing trench or cellar foundation supports the concrete blocks which, when mortared into place, will form the 8-by-12 foot cellar.)

3. Dig a trench all the way around the bottom of the hole between the marked lines. Excavate 16 inches wide and 9 inches deep. To create a level footing for the block walls, tamp down the bottom of the trench until it is level. Build a footing form from 2-by-4 inch lumber. Make sure that the form is level. Dampen the soil with a garden hose or buckets of water, then fill the trench with ready-mix concrete. Level the wet concrete with a trowel and allow to dry.

4. Ensure that the concrete blocks fit the footing. Lay them in place without mortar. Locate the blocks 4 inches from the inside edge of the footing. Slip a strip of plywood between each block to allow for the mortar. Lay nine blocks on each side lengthwise. Lay five blocks between them on each end of the footing. Place blocks with the large core side down. If required, adjust the blocks as needed to fit the footing. Mark the placement of each block with chalk. Remove the blocks.

5. Spread a layer of mortar (1 by 8 inches by the length of two blocks) along the chalk line, down both sides. Start at a corner. Set the corner block in place and align plumb and level. Remove any excess mortar. Continue to lay the blocks around the footing. Lay blocks in layers, continuing until the walls are 11 blocks high all the way around.

6. Pour 2 inches of coarse gravel around the outside perimeter of the base of the concrete blocks. Lay a 4-inch perforated drain tile or pipe on top of the gravel with the holes pointed downward. Create a 2-inch slope to the pipe from back to front. Use 90-degree joints at the corners to connect the pipe sections. At each end of the "U," dig a 3-by-3 foot hole and fill with gravel. Install another joint of pipe to extend the drainage tile pile into the center of the hole.

7. Mark off a 32-inch-wide opening for the cellar doorway. Position the door opposite the entrance ramp. Construct a door frame from pressure-treated 2-by-6 inch lumber. Position the door frame on the first layer of blocks and support temporarily with scrap lumber or concrete blocks. Nail the framework to the concrete with 2-inch concrete nails. Install a standard, solid wood door for the interior door into the cellar. Attach the interior door to the door frame with three 6-inch T-hinges using wood screws. Install a hook and eye on the outside of the door to hold the door closed. Attach a door handle at a convenient height using wood screws.

8. Finish constructing the concrete block walls of the cellar around the door frame. Build a lintel over the doorway using lintel blocks (especially shaped concrete blocks with a channel cut in the top to accommodate a length of rebar steel rod for reinforcement) end to end to form a channel. Place rebar in the channel and fill with mortar. Let dry, turn over and mortar into place.

Finishing the Cellar Project

1. Use pressure-treated 2-by-4 inch lumber to build the framework for the stairway wall and hatchway door. (The exterior doors lean inward to form the hatchway.) To build the hatchway door support and stairway walls, construct a frame of 2-by-4 inch lumber around the door opening. Attach the framework to the concrete with concrete nails. At right angles to the boards that frame the doorway, build a 2-by-4 inch framework, on 16-inch spacing, for the the stairway walls. The bottom board (2 by 4 by 70-1/2 inches) should match the ground slope. Nail firmly in place with 2-inch spiral shank nails. Repeat on the other side of the door frame.

2. Install insulation bats between the door frame and the concrete blocks. Stuff insulation into any gaps or use foam insulation to fill voids. Cover the exterior of the framework with pressure-treated 1-inch plywood. Attach the plywood to the door frame with 2-inch spiral shank nails, driven at a 30-degree angle for added strength. Paint the plywood with waterproof paint or sealer.

3. Build the hatchway doors from 1/2-inch plywood. Cut four pieces 21 1/2 by 96 inches. Frame two of the pieces with 2-by-4 inch boards. Nail in place. Fill the cores with insulation, cover with the other two pieces of plywood and nail in place. On the right-hand door, along the edge, attach a 1-by-6 inch board the length of the door. This board will overlap the opening and prevent drafts when the doors are closed.

4. Start to build the roof. Attach 2-by-8 inch pressure-treated boards to the top of the concrete block walls by drilling holes in the boards for the concrete anchor bolts you embedded into the concrete. Fasten the top plate firmly in place with nuts.

5. Cover the roof framework with 1-inch exterior-grade pressure-treated plywood and nail in place using 2-inch wood screws spaced no farther than 8 inches apart. Install a vent pipe by drilling a small hole between the second and third rafter from the rear wall. Use a keyhole or saber saw. Starting from this hole, cut a 6-inch-square hole, centered between the rafters. Cut an 8-inch section of window screen. Staple the screen to the underside of the hole to keep out insects and vermin. Cut two 7 1/2-inch pieces of 1-by-2 inch lumber. Cut a 7 1/2-inch square piece of 3/4-inch plywood. Attach the plywood to one of the 1-by-2 inches pieces using a 3/4-inch leaf hinge. Close one door against the other and secure with a hook and eye fastener. On the top of the cellar roof, screw the plastic flange into the plywood after centering it over the hole. Slip a 4-inch length of plastic pipe into the flange, tapping gently with a hammer. Caulk around the bottom of the vent. Install the galvanized hood on the top of the pipe.

6. Cover the roof with tar paper and secure with roofing nails.

7. Seal with caulking around the base of the vent pipe. Cover the roof with the soil you removed when the cellar was excavated.

Adapt the Cellar to Your Needs

1. Install electric service, if desired. Electrical power is not needed for the operation of the cellar--just use a lantern or flashlight. However, if you use the space as a shelter, electric power is an important consideration. To install electric power, bury a No. 14 underground cable from an outlet or box at your home or garage and enter the cellar at the roof line. Install a light fixture. The warmth from a light bulb or two can significantly raise the temperature in the cellar on the coldest of nights.

2. Consider pouring a concrete floor. A dirt floor is preferable for storing fruits and vegetables; however, a concrete floor is more comfortable for shelter use.

3. Build four bunk beds if shelter use is anticipated. Build from 2-by-6 inch by 8 foot spruce lumber and 1-inch plywood. The wooden bunks will provide deep shelving when not used as a sleeping platform. Add metal shelving or build shelves yourself from 2-by-8 inch lumber cut to the lengths desired. Mount with concrete anchor bolts and metal shelving brackets.

4. Stock the shelter with a first aid kit, sanitary supplies, bottled water and provisions for at least a week. Be sure to include a battery-powered radio, cell phone and flashlight.

Tip

If you do not have enough dirt to cover the roof with at least 2 feet of soil, bring more in to finish the job. Dirt is the cheapest insulating material available, so do not skimp on adding more dirt. When the cellar is completely covered, scatter grass or flower seeds. Mint makes an excellent groundcover. Growing vigorously, mint produce a thick and binding root system to hold the soil in place.

Warning

Follow safety guidelines when working with power tools. Always wear ear and eye protection.