A Partial Underground Structure
If your location is not ideal for excavating a root cellar, you can build a partial underground structure by digging just four feet or so into the ground. This type of structure is common in colder parts of the country, in areas where the ground is flat and rocky, or where the water table is high and there is very poor drainage. The walls of a partial underground root cellar are usually made of masonry blocks and banked with soil on three sides.
First you will need to decide on the size of your root cellar. For example, if you want a structure twelve feet by eight feet that will stay solid for years, you will need to dig an area sixteen feet by twelve feet that sits four feet deep with an entrance ramp that is four feet wide and slopes six feet. You want the area to be larger than your structure so you have access to build your walls from all sides. You can fill in the extra space on the outside of the wall once it is built with the dirt from the excavation; this will provide even more insulation for your root cellar. The entrance ramp is six feet long and angled giving you an area to make steps leading down to the main door of your cellar. Make sure you have the space to accommodate the size structure you want to build before you start digging.
If you do not want to spend money on concrete blocks, you can try to find used ones from building teardowns, use cedar logs stacked on end, or install large stones mortared together. The most important thing to remember is you want your root cellar walls to be strong.
This type of structure traditionally has a hatchway door with a stairway leading down to a second doorway. The “double entrance” offers great insulation from the outside temperatures because of the air space between the two doors. The roof is typically made of two by fours, and then protected with roof sheathing and plastic film with dirt piled on top of everything. Vents are installed for good air circulation, and a drainage system is used to protect veggies and fruits.
Two big advantages to the partial underground structure are that it is affordable and easy to build. If you utilize common materials from your own property or a local building supply store, you can build this structure in your spare time.
Completely underground root cellars usually stay at the ideal temperature for storing fruits and veggies due to the earth's natural insulation. However, you can still preserve successfully in an above ground storage building as long as you build in the right location and provide insulation and proper drainage. Constructing a solid above ground structure begins with choosing the right materials for its walls.