A root cellar gives you cool, dark, humid storage with no electricity bill. Because the earth around it stays at a stable temperature, a well-built cellar can keep vegetables, fruit and canned goods in good condition for months. It’s one of the more practical investments a gardener or homesteader can make.
It’s also a project you only want to do once. Getting the location, drainage and structure wrong is expensive to fix after the digging is done. This guide walks through the decisions in the order you’ll face them: where to put it, what type to build, what to build it from, how to construct it, and how to keep it working.
Choose the location #
Stay close to the house. A cellar near your home is easier to reach in bad weather, and it makes moving produce straight from the garden or kitchen to storage far simpler. Also look at proximity to your garden, and make sure nothing obstructs construction.
Check drainage first. This is the single most important siting decision. A cellar in a spot that collects water or floods will be damaged and its contents ruined. Pick ground that slopes away from the cellar. If the site is marginal, you’ll need to grade the area or install a drainage system, or choose another location altogether.
Look at climate and temperature. Root cellars work by using the natural insulation of the earth, so you want a site with relatively stable temperatures year-round and no extremes of heat or cold.
Plan access. You’ll be carrying heavy crates in and out. Make the entrance wide enough for comfortable passage and set it at a height that limits strain when loading and unloading.
Decide on size and type #
The right size depends on how much you’ll store: your family’s needs, the size of your garden, and how often you shop. Leave room for shelving and for walking and maneuvering. Err on the larger side, because your needs will probably grow. Make the ceiling tall enough for hanging baskets and tall shelves.
There are three common types. A traditional underground cellar is dug into the ground. An earth-sheltered cellar is built into a hillside or mounded over with soil. An above-ground cellar uses insulation instead of depth. Each has advantages and trade-offs, so research the one that suits your property and climate.
Plan the layout on paper first. Separate sections or compartments let you store different produce under different conditions, and shelves, racks and bins keep things organized and let air move around them.
Gather materials and tools #
Make a complete list before you break ground.
Materials. For structure, concrete, stone or brick resist moisture, rot and pests and give excellent insulation. You’ll also need roofing material, insulation, flooring, and parts for ventilation and lighting. Consider locally sourced materials, which have less environmental impact, and recycled or reclaimed components where they’re appropriate.
Tools. A shovel, pickaxe, level, measuring tape, hammer, nails, drill, saw and a wheelbarrow cover most of the work. Having everything on site beforehand saves time and frustration.
Prepare the site #
- Clear and level. Remove vegetation, rocks and debris, and level the ground so the cellar sits on a stable foundation.
- Excavate. Dig to the size and depth in your plans, by hand or with machinery, keeping the walls straight and even. Dispose of the excavated soil in line with local regulations.
- Handle moisture. Apply a waterproof sealant or membrane to the walls and floor, ensuring a tight seal. Because an underground cellar is exposed to ground moisture, use a moisture barrier or waterproof coating on walls and flooring for extra protection.
- Create the entrance and ventilation. The entrance can be a traditional door or a trapdoor with stairs. Install the ventilation system at this stage too.
Build the structure #
Walls. Use whichever material you chose, and make sure the walls are strong, level and well insulated. Follow proper construction techniques.
Support. Structural integrity matters for both longevity and safety. This is especially true in unstable soil or where the water table is high. Talk to a qualified contractor or structural engineer about beams or reinforced walls. A collapse inside an underground space is a serious danger.
Roof. The roof insulates the space and protects it from the elements. Use appropriate roofing such as metal or shingles, and install it so it doesn’t leak or transfer excess heat.
Insulation. Rigid foam board or fiberglass batts go between the walls and roof. Seal any gaps and air leaks, since insulation only works if it’s continuous. Insulation holds a steady temperature, protects food from swings, and prevents condensation.
Floor. Pick something moisture-resistant, sturdy and easy to clean: concrete, stone, tile or a durable epoxy coating. These resist rot, pests and moisture damage. A layer of insulation beneath the floor helps regulate temperature and stops moisture seeping up.
Door. The door should seal tightly to prevent heat loss and keep pests out. It should be wide enough for easy access and have a reliable lock. Steps or a ramp make entry safer.
Ventilation, temperature and humidity #
Proper airflow keeps excess moisture from building up and prevents mold and mildew. Choose a system that suits your design and location: passive air vents, powered fans, or in very hot regions, air conditioning for tighter control. Position passive vents to use natural air currents. If you use fans, consider noise, energy use and location. Adjustable vents give you control over both temperature and humidity.
Different produce wants different conditions, so learn the requirements for what you intend to store. Put a thermometer and a hygrometer in the cellar, in different spots to catch variation, and record readings regularly. Deviations are your early warning.
To control temperature naturally, locate the cellar in shade, channel cool air through underground ducts, or use evaporative cooling. If that isn’t enough, add cooling equipment, sized appropriately and with an eye on energy use. For humidity, dehumidifiers and sensors can prevent either dampness or drying out, which extends the shelf life of produce and keeps mold and bacterial decay at bay.
Adjust with the seasons. Outdoor temperature and humidity change, so ventilation settings or insulation may need tweaking through the year.
Lighting and security #
Cellars are meant to be dark, but you need to see. Low-energy LED lights give strong illumination while producing little heat, which protects temperature and humidity. Place them to cover the whole space. Small windows or light tubes can add natural light if sealed to prevent heat loss, though they’re optional.
For security, install a high-quality lock, such as a deadbolt or electronic lock, and inspect it periodically. A cellar full of stored food is worth protecting.
Shelving and organization #
Build shelves that suit what you’re storing, from moisture-resistant materials such as stainless steel or treated wood. Make them sturdy enough for heavy loads, and adjustable if possible, to take different sizes of produce. Leave room between shelves for access and maintenance.
Use bins, crates and racks for root vegetables and preserving jars that don’t suit shelves, and hang onions and garlic from baskets or racks to use vertical space. Group similar produce together and arrange it by shelf life. Humidity-controlled storage bags or containers help for items that need them.
Label everything with its name and storage date, using waterproof labels or markers that won’t smudge in condensation.
Keep it clean and pest-free #
Cleaning. Clean shelves, walls and floors regularly with mild, non-toxic cleaners and avoid harsh chemicals that could contaminate your food. Dry all surfaces before restocking. Remove spoiled or decaying items promptly to stop mold or pests spreading.
Mold and mildew. Prevent them with ventilation, good humidity control, and fast action on leaks or standing moisture.
Pests. Seal gaps and cracks, screen the vents, and set traps or baits where needed. If you prefer non-toxic deterrents, lavender, mint and bay leaves are options, as are non-chemical traps and barriers made for food storage areas.
Rotation. Inspect the stored food regularly, rotate stock so older produce is eaten first, and keep shelves organized so problems are easy to spot.
Maintenance and backup #
Inspect the cellar periodically for water seepage, cracks in walls or floor, and signs of pests. Check that ventilation and temperature equipment work properly. Repair or replace damaged parts, and confirm seals and insulation are intact.
If you rely on powered cooling or ventilation, plan for failure. Evaporative cooling or a supply of ice packs or blocks can hold the temperature until normal systems return. A generator or battery backup keeps fans, cooling and lights running through an outage.
The best root cellars do most of their work without power at all. Site it well, keep it dry, insulate it properly and keep it ventilated, and it will store your harvest through the winter and beyond.
Related reading: Food and water guide; best ways to preserve food naturally; preserving food without refrigeration; rotating your food supplies