Root Cellar - DIY

Root Cellar - DIY

Food storage is an essential component of rural survival. Enough food for one winter per person is a good start and work up to storing one years worth. Ideally we want to grow as much food as possible and buy or trade in bulk for the rest. However all that food will become spoiled and useless in a short time if not stored properly. The main concern is temperature, the food cannot be allowed to freeze or reach room temperature.

Most food out of a garden will not keep unless canned, dried or frozen. The natural keepers like potatoes, onion, garlic and winter squash will last through most of the winter if kept in a consistently cool, dark and dry environment. Dried food like sacks of grain, nuts or dried fruit are more forgiving but they too will last longer under those conditions. What we need is a root cellar.

Root cellars are the traditional food storage structures, called as such because they were dug into the ground or bermed up with earth to approximate a cave for temperature control. Deep caves have a steady temperature year around, independent of the air temperature outside whether a deep freeze or a withering heat wave.

Root cellars can be built below the house, in the basement, outside as a stand alone structure or even as just a closed off area of the house itself. The main concern being insulation from the surrounding air temperature. Food is best kept in a dark, dry and consistently cool area.

The pictures shown are of a modest root cellar built into the north side of a house. It's a step down room about four feet below floor level with a cement floor and knee wall bermed up with earth on the outside. Above the knee wall and interior walls are about a foot thick and insulated. It has two small windows for light and venting. It works well as food and homemade wine storage for two people. Note the thermometer on the wall for temperature monitoring.

Cement floor root cellar on the north side of the house with earth berm insulation. / About 100 sq.' in size. /
Small window for light and vent.

An interesting fact is that a root cellar with an insulated floor is more apt to freeze in extreme low temperatures than an uninsulated floor such as plain dirt or cement. The reason being the earth itself gives off constant heat which may not seem like much but when the air temperature is zero, constant 40 F degrees is warm by comparison. When insulation cuts off that warmth freezing can occur.

If you have a un-seaworthy fiberglass boat that you can't get rid of you can convert it into a root cellar as here.

Burying an ocean going container maybe the fastest way of having a root cellar that is secure and bug proof. Even a partial burial with enough earth berm thickness on the sides and a mound on top would work. Another alternative which maybe more cost effective is to enclose the container with a straw bale shell, similar to building a straw bale house except with the container serving as the frame. Cost effective in the fact that the bales of straw would be cheaper to buy and have delivered than hiring a backhoe or an excavating machine to dig a big hole, devise a drainage system and placing the container in it. However a free standing, above ground straw bale root cellar is the way to go as the least expensive choice. If I did not have a container, that would be my choice.

20' container planned for a root cellar.

Bales of straw are stacked like interlocking bricks against exterior surfaces with steel rebars rammed through the bales to add stability. The bottom row would be off the ground and the outer surfaces sprayed with plaster or stucco for weather and bug proofing. A roof, even a flat one, can be laid right on top without snow load worries. Ideally the doors would face north with some sort of an airlock or a thresh hold entrance so hot outside air during summer will not rush in when opened.

Big straw bale in field. /
Straw close up. /
Straw should not have leaf or seeds.

Average straw bales in our region measure 18"Wx14"Hx36"L and weigh about 35lbs. and cost $1.50 to $4 a bale at a feed store, the price fluctuating on the growing and harvesting weather. Approximately 200 bales are needed to cover a 20' ocean container. Buying in quantity from a farmer directly should lower the price.

The big disadvantage of fiberglass insulation is that it requires a frame to hang it in. Any thickness beyond 6" and the lumber required becomes cost prohibitive and any sort of double wall construction would be tricky and time consuming. Foam is the most expensive of insulating materials and also require some sort of frame to set it in.

If I were to build a house, I would choose the straw bale construction. I plan on using straw bales to convert my container to an above ground root cellar and also to insulate a large above ground water storage tank.