Quickly into the research and design of the root cellar, it was obvious that a stick-framed cellar of ponderosa pine would only last about 4-5 years in the ground. Not gonna cut it.
After a bit of digging around and consulting with some experienced builders, a root cellar design emerged that uses locally abundant waste materials, the indigenous materials that lay within the Pine Ridge area.
Rammed Earth Reused Tires
Heaps of tires sit in dumps not only in Pine Ridge but across the United States and greater parts of the world. By using them to construct the walls and foundation of a structure, you are able to build an incredible building envelope that has thermal mass, fortified resistance to bending and compression– the tire walls can resist earth, snow and wind loads, and won’t rot in the presence of moisture.
The process of ramming the tires is tedious, but simple. It requires an dirt and a sledgehammer or tamping tool. Instructions to follow have been documented by many builders across the internet as well as in Michael Reynolds’ Earthship books. Visit the Earthship Biotecture website for more information: http://earthship.com/ .
A precedent that was offered from Mike of Touch the Earth Ranch has shown a modified method of ramming tires, with instructions and accompanying pictures that give clues to the connection between the tires, the top plate, the plastic membrane and the roof: http://touchtheearthranch.com/goatshed.htm
Parallel Chord Pallet Trusses
In searching for the right kind of hat (roof) for this root cellar, I stumbled upon low cost truss that was an adaptation from Alfred von Bachmayr’s pallet truss design. Ironically, it was adapted FOR the Pine Ridge Indian Reservation because of its abundance in tapered, small diameter pine poles. You can visit Dr. Own Geiger’s website for more information on the construction of the truss: http://www.grisb.org/publications/pub7.htm .
Small diameter poles can be used as structural members for the truss, serving as the top and bottom “chords” that are reinforced by pallet slats arranged at 90 degrees from one another, alternating sides.
Some key highlights of this truss design:
– Using poles eliminates the awkward and time consuming process of assembling pallet wood for the chords.
– Full-length poles are stronger than numerous short pieces of pallet wood assembled together. Any component is only as strong as its weakest link – one poor joint could cause a structural failure.
– This truss provides sufficient roof insulation where temperatures can range from minus 29 degrees to 120 degrees Fahrenheit. You can space the chords out anywhere from 16-24″. This leaves a lot of room for insulation. KEY in this climate, and especially for a root cellar roof.
– Very few tools are required. These trusses are virtually free.
By utilizing the building systems and taking the steps that others have made before us, a low-cost yet highly efficient root cellar has become possible.
Earth-filled tire walls can withstand the weight of the earth and other live loads– snow and wind (Strength and Durability, check.)
The trusses, above ground, will contain a large amount of space for insulation (Consistent Temperatures, check.)
The roof will be positioned down-slope of the site, so water runoff can continue its way down the watershed. The rubber tires act as a vapor barrier on the outer side of the cellar. French drains will be installed around the perimeter of the building. The gravel floor will have a slight grade to prevent puddles and flooding during exceedingly rainy days (Drainage and Water Control, check.)
Tires? Free. Pallets? Free. Pine Poles? Free.
This design uses a small amount of dimensional lumber for the top plates, door frames and sheathing. These can range from repurposed materials to rough cuts to store-bought, depending on the available resources and funds.
1-2 Plastic membranes to shield exposed wood from the elements.
Hurricane ties should be fixed to the trusses/top plates to ensure that high wind won’t kick up the roof.
A 6″ Diameter Vent Pipe is the standard size for this cellar footprint ( 6’2″ x 6’8″)
With just a little bit of variation, these building systems wield the potential to construct low-cost, energy efficient homes!