A root cellar keeps food at 2-10 °C and 85-95% humidity, ideal for storing root vegetables, apples, cabbage and some preserved foods for months. It works by using the steady cool of the ground instead of fuel, and it needs ventilation so the air stays fresh and the temperature stays low.
A root cellar is an underground or earth-covered room that keeps vegetables and fruit cool and humid without refrigeration.
Cool And Humid Are Both Required, And The Ground Supplies Both
Root vegetables need cool and humid storage: a cellar as a whole holds 2-10 °C and 85-95% humidity. Most of the work is done by the earth around the room: it stays cool in summer and does not freeze solid in winter if the room is deep or covered enough. Humidity comes from damp soil and from the produce itself. The building’s job is to keep out frost, heat, light and rodents while letting stale air out and cool air in.
Three child pages cover the details: Excavation & Construction, Temperature & Humidity Zones and Shelving & Organization. For basic underground building methods, see Underground and Earth-Sheltered Building. Other pages on cellars: Root Cellar Build, Root Cellars and Cellar Construction.
What You Need
- A site that drains, ideally a cool north-facing slope close to the garden
- Digging tools and a way to support the walls and roof
- Ventilation pipes or openings, low for incoming cool air and high for outgoing air
- Shelves, crates and damp sand for the produce
Method: Plan A Cellar
Step 1: Choose the site. A north-facing slope close to the garden is ideal.
Step 2: Dig, line and roof it. See Excavation & Construction.
Step 3: Ventilate. Fit a low inlet and a high outlet. Open the door on cold, dry nights to cool and dry the room.
Step 4: Organise by zone. Cooler spots for roots and apples, warmer ones for onions and cured meats.
Step 5: Check the temperature and humidity. A thermometer on a cord and a feel for damp tell you more than any sum.
Common Mistakes
- No ventilation — stale air, rot and, in a sealed room, a gas hazard.
- Wet floor and walls — drainage first.
- One shelf for everything — different foods want different spots.
Safety
Collapse and bad air in cellars
A cellar dug into the ground can collapse while it is being excavated, and a roof of earth is very heavy. Stored produce respires and uses up oxygen; a poorly ventilated cellar may hold air short of oxygen or rich in carbon dioxide. Ventilate before entering, never enter alone, and do not test the air with a flame. See Cellar Construction, which treats the cellar as a confined space from the first day.
What’s Next
- Learn next: Excavation & Construction — building it
- Combine with: Temperature & Humidity Zones — arranging the contents