Interactive lesson

Root cellar, step by step

Interactive lesson: choosing the type of cellar, the site, safe digging, walls and an earth roof, ventilation, a basement cold room and shelving.

Free sample Chapters 1 and 2 (8 steps) are free. The full lesson comes with the module “The root cellar: building and fitting out”. Already bought? Unlock

This lesson is general guidance, not professional training. Local regulations and expert advice always take precedence. Read our disclaimer.

The whole lesson as text

1. Which cellar you need

A good cellar is a cold, damp box that breathes.

Partitioned corner — The north corner of an existing basement, insulated from the house, with two air pipes. It is the cheapest option and needs no permission for a new building.
Cellar in a slope — Half-buried, with a side entrance at ground level. Water drains away and it is easy to ventilate, but it needs a slope and dry ground.
Buried, earth roof — A free-standing buried cellar has the most stable temperature. It is the most expensive: structure, permission and water.
Measure first — Before building a new cellar, spend the first winter measuring temperature and humidity in the spaces you already have. Often it is enough to partition and insulate what you have.

Why: A modern basement under the house often sits at 15 °C (59 °F) and is as dry as a loft: fine for jars, poor for potatoes and apples. The difference comes down to three things: how much earth surrounds the space, how much heat comes in from the house, and how the air gets in and out.

A family of four needs roughly 4–5 m² of floor (43–54 sq ft) and a height of 2–2.2 m (6 ft 6 in–7 ft 2 in).
Lower than 2 m and you work stooped; higher means more digging and warm air under the ceiling.

2. Site and soil

A cellar must be dry from groundwater, and kept cool, away from the house and the sun.

Test hole — Dig a 2.5 m deep test hole and look at it in March or April, when the water is highest. If water seeps in below 2 m, a buried cellar will not work: build it into a slope or half-buried.
North and slope — Entrance and the largest wall to the north or north-east. A gentle north-facing slope is ideal: level entrance, water drains away, less digging.
Away from trees and barns — Roots break through walls and draw water, so as a guide stay at least as far away as the crown of a mature tree. Keep away from the septic tank, muck heap and livestock buildings too.
Close to the kitchen — You go to the cellar every other day, in snow too. A firm path, no mud, with lighting.

Why: A south side warms up in summer and the cellar will not cool down until December. Clay soil holds water and swells, so it pushes on the walls. Sandy and gravelly soil is dry but collapses easily when dug.

Ask the neighbours how their well and cellar behave.
Before digging, find out where water pipes, power cables, gas and drains run: in the UK and Ireland ask the utility companies for their plans, in the US call 811 a few days before you dig.