The plans in this post were created by the Canadian Ministry of Agriculture in the 1940s. The original text accompanying the plans has been summarized.
These plans are for historical interest only and are not consistent
with modern building practices, but it’s still interesting as a starting point
for anyone looking for a low-tech, simple solution for winter produce storage.
At the very least, should you decide to adapt this plan for
your own use, consult a building professional and use modern, pressure-treated lumber
and/or reinforced concrete in place of the regular wood members that are suggested
in the following summary.
How to Build Your Own Root Cellar
(Circa 1941)
There are different ways to store vegetables, but the root
cellar has proved to be one of the most practical in locations where low winter
temperatures are common. Recycled materials in good condition can be used to
construct the root cellar to keep costs low.
There are several vital factors to keep in mind when
planning and constructing your root cellar:
Location
The ideal location for a root cellar is on the side of a
hill so that rainfall will drain away from the cellar during periods of heavy
rain. If possible, orient the door of your cellar to the south to allow
sunlight and air circulation to keep the interior of the cellar dry, although
many root vegetables (potatoes in particular) should not be shielded from the
light.
Temperature
The optimal temperature for storing most vegetables is
between 35° and 40° F. There are exceptions: Potatoes like to be kept around
60° F for the first two weeks after harvesting. This higher temperature allows
injuries to the potatoes to scab over. No vegetables should be allowed to
freeze. The freezing point of potatoes is about 28° F.
Humidity
Too much moisture will cause vegetables to spoil. Condensation
on the walls and ceiling indicates the humidity is too high in the cellar. Too
dry an atmosphere can also be harmful. The best condition is to keep the cellar
fairly humid but not sufficiently high to cause condensation.
Ventilation
Cellars should be vented. Lack of air circulating in the cellar will result in spoiled vegetables. Circulation of air in the root cellar prevents condensation of moisture on the walls and the ceiling, resulting in firmer vegetables, provided the temperature is maintained within a proper range. Ventilation is especially important during the cold weather when the doors must be tightly closed to prevent freezing. A common practice is to draw air in at one end and out the other by intake and outlet ventilator stacks. Design air intakes and outlets with the means to partially close off the ventilators during extremely cold weather.
Plan of Farm Root Cellar
An overcrowded root collar is not efficient in keeping the
vegetables in a firm and fresh condition. For the average farm where vegetables
are stored principally for family table use, a root cellar of 10 x 14 feet,
inside measurement, is usually large enough.
To guard against the temperature in the root cellar becoming
too low during the winter and too high during the summer, excavate to at least
six feet below ground level, and allow for a thick and well-insulated roof.
The upright wall posts, plate, and ridge poles can be made
from six- or eight-inch poles or can be made from 8 x 8-inch stock lumber. The
illustrations show a root cellar 10 x 14 feet, using two 18-foot ridge poles,
two 14-foot poles for the plate, ten 7-foot posts, and eight-foot posts.
The upright posts should be set on planks or flat stones to
prevent them from sinking into the ground and should be suitably braced. The
ridge poles and the poles for the plate are set along the top of the upright
posts, which are recessed on top to receive the poles. The floor plan of the
cellar, as shown in figure I, indicates the arrangement of the upright posts.
It is important that the walls be well insulated in order to
prevent the vegetables at or near the walls from becoming frosted. A cheap
method of providing insulation is to use a tight packing of chaffy straw held
in place by chicken wire netting or page wire fencing. The wire is stapled to
the inside of the wall upright posts, and the straw is packed in tightly
between the wire and the wall of the excavation.
Allow for an adequate alleyway running through the center of
the cellar between the bins. When building the walls of the bins, a space
should be left between the boards to allow air to pass through the bins. This
is illustrated in figures 2 and 3. Slatted floors in the bins will also help
the air circulate around the stored vegetables, and if these can be installed
without too much additional expense, it is wise to put them in as they will add
to the efficiency of the root cellar.
The roof can be boarded in with lumber of fairly heavy stock
to support the weight of the heavy roof insulation. Another method of closing
in the roof, which has the advantage of being very inexpensive, is to use small
poles laid tightly together across the width of the roof with a matting of
willows or brush placed immediately over the poles.
To provide for ventilation, an air intake and air outlet,
about 12 inches square for the size of the cellar as illustrated, should be
installed. These ventilators should be placed at opposite ends of the cellar,
with the air intake at the front, and should rise about five and one-half feet
above the roof boards so as to extend well above the roof insulation. T
The air outlet begins at the ceiling. The air intake
branches just below the ceiling, one branch on each side of the alleyway and
extending to about one and one-half one on each side of the cellar at the
opposite end to the outlet extending from above the surface down along the wall
and coming out through the floor. The air intake and outlet, in any case,
should be built so that they may be regulated, as it may be found necessary to
partially shut off the ventilators in cold weather.
The root cellar entrance should have double doors at least
four feet apart. The vestibule between the doors acts as an insulating space.
The doors should be well built and large enough to allow easy passage in and
out of the cellar with vegetables.
When insulating the roof, it is a good practice to place one
or two layers of heavy tar paper over the roof boards before any further
insulation is put on. Besides affording some insulation against frost, the tar paper
will prevent any moisture from seeping through and falling onto the vegetables.
Alternate layers of straw and soil should then be put on; the straw in layers
about six inches thick when compressed and the soil in layers from eight to
twelve inches thick, until at least three and one-half feet of good insulation
is secured. Where each straw layer meets the ground level, a small trough
should be dug in the soil and packed tightly with straw.
Root Cellar Management
Inspect the root cellar frequently to make certain the
ventilators are allowing good circulation of air and preventing condensation of
moisture on the walls and ceiling. During the winter, there are times when it
may become so cold that there is a danger of freezing. At such times it is wise
to shut off the ventilation for a while. The use of lanterns or a small coal
oil stove in the cellar may furnish enough heat to protect the vegetables from
frost when the weather becomes excessively cold.
After early spring, when the air becomes warmer, the doors
and ventilators may be opened at night and closed during the daytime to keep
vegetables dormant for a longer period of time. The potatoes in the cellar
should be picked over several times before spring, and any sprouts that have
formed should be removed. This practice will keep the potatoes firm and
minimizes the danger of spoiling.
The root cellar is not a costly structure to build. The
important points of construction should be carefully followed to ensure good
vegetable storage. A good root cellar will quickly repay for the expense and
time involved in construction.
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