I’ve been asked a few times about building a safe storage room apart from a main house structure, such as root cellars and such. My recommendations have been to do it as the old timers used to do it, because time has proven their designs work with excellent results. With that in mind I came across this old article that gives step by step instructions on building your own concrete root cellar set into the side of a hill. If you have no hill you could even excavate a hole in the ground deep enough to build this into, and add a stairway down to the door of the structure. Just remember a couple of important points here; never build a root cellar with a floor lower than the applicable water table level for your placement of the structure, and always make sure the majority of the structure is under the level of the ground where you build it. Also make sure there is plenty of drainage around the structure to avoid water damage and leakage of the structure.



A Concrete Root Cellar of Practical and Inexpensive Construction and Attractive Design.


The outside cellar built into a bank or partly underground is only a development of the old system of burying potatoes, cabbages, and so forth, in a barrel or, as was sometimes done, in a mere hole in the ground for winter storage. The advantages of the new method are obvious, but unless the cellar can be kept dry and clean it is little more than useless. For this reason great care must be taken, first in selecting the site and second in the choice of materials with which to build. It is essential that the site should be well drained and dry under normal conditions, as continual dampness outside, no matter how carefully the building is constructed, will cause decay inside. The cellar may be built into a bank or may be partly underground. In the latter case a small cellarway with cement steps protected by a door should lead to the entrance.

Assuming that the site chosen is in a bank and that concrete is the material to be used, you will begin by digging a hole the size desired for the building, allowing six inches on all sides for the thickness of the walls. Arrange for your finished floor to be two or three inches above the natural grade at the front. Next dig trenches for the footings and foundations. The footings must always be below the frost-line, generally from three to four feet below the surface, and must be level. As the bank rises toward the back it will not be necessary to go down so deep for the footings in the rear as in the front, but the difference in level must be gained by a step and never by a slope. If the soil is firm and solid the “spread” of the footings may be omitted.

When the digging is completed mix the concrete for the footings. A mixture of one part Portland cement, two parts sand and four parts gravel will be required for the foundations, walls and roof, and a 1-2¼ -5 mixture for the floor. Mix the materials together on a tight board platform, using enough water to wet them thoroughly. Pour the concrete into the footing trenches and ram it clown. If the “spread” of the footing is omitted the entire foundation trench may be filled to the floor level, using the earth sides as forms, since the wall would be of the same thickness from top to bottom. Otherwise wooden forms will be required from the top of the footings up.

These forms are made of one-inch boards nailed horizontally to 2 x 4 uprights spaced two feet apart to form a box without top or bottom and with a space of six inches—or the thickness of the finished walls—between the sides. The uprights, of course, will be on the outside. It will be easier for a building of this size to build the forms on the ground and then raise them to position. Nail cross cleats to the tops of the uprights to keep them at the proper distance apart, and brace the forms in the center to prevent bulging. The forms should be held firmly while the concrete is being poured.

The simplest and surest way of forming the door opening is to set the door-frame in place when the forms are being built. Drive iron ties into the sides and top of the frame, two in each side and one in the top, so that they will extend into the concrete walls. If the ties generally used for this purpose are not available heavy nails driven into the frame will serve very well. When the wall forms are built and the door-frame is set in place pour the concrete in layers about six inches thick and tamp each layer lightly with a wooden or iron rammer until the water shows on top and no stones are left uncovered by mortar. If a spade is forced in between’ the concrete and the boards and worked up and down and sidewise it will force the stones back and bring a coating of mortar to the outside, thus giving a smooth surface to the face of the wall.

When the concrete is filled to a level of two inches above the top of the door-frame lay two half-inch iron bars or old wagon tires in the fresh concrete with the ends extending at least eight inches beyond the sides of the frame. This will form a re-enforced lintel over the doorway. The walls are then filled to the top, the end walls being carried to the peak of the roof. Before the concrete at the top of the end walls hardens ½ inch iron bars 18″ long must be driven into them to a depth of 9″. Place them 24″ apart. Next nail 2×4 rafters to the tops of the inside uprights of the side walls giving them the slope desired for the roof, ands spike them together securely where the meet at the peak or ridge of the roof.

Nail one-inch pieces horizontally across the building to the bottom of each pair of rafters. These pieces are called “collar beams” and are to prevent the rafters from spreading when the weight of the concrete is placed on them. Next nail one-inch boards on top of the rafters and nail a form for the cornice to the tops of the outside uprights. Bend the projecting ends of the half-inch bars down to within 1½ inches of the roof boards. Two one-inch iron rods should be laid on top of the wall outside of the upright bars and extend entirely round the building. Cover the entire roof with heavy woven wire fencing securely wired to the iron bars and extending to the edge of the cornice. Use pieces of drain tile to form ventilators.

Next spread 1½ inches of concrete over the entire roof, beginning at the cornice and working toward the ridge. The wire must be lifted as this concrete is placed, so that the wire will rest on top of it. On this lay 2½ inches more of concrete. Tamp it until the moisture comes to the top and give it a smooth surface with a trowel. The work of laying the concrete must not be interrupted, as a joint between the fresh concrete and that which has hardened would probably cause a leak. While it is drying the roof should be protected from the sun by canvas or boards placed a few inches above it, and should be wet morning and evening for a week to prevent cracking. Place galvanized iron hoods over the ventilators. The forms may be removed in a week or ten days and a four-inch concrete floor laid.

From Gardeners Chronicle of America May 1911


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