The paper to be used can come from a variety of sources. Newspaper, junk mail, magazines, books, etc. obtained from the local dump or from waste bins are all useful. Depending on the type of mixer used to pulp the mix, the paper may be soaked in water beforehand.
A typical homemade mixer uses a small electric motor mounted directly on a shaft with two four-inch square blades attached, resembling milk shake maker. This shaft is suspended in a plastic 55 gallon drum to mix the material.
Another homemade mixer is made from a trailer built from the rear end of a car, with the differential input pointed upward and a lawn mower blade attached. When the trailer's wheels turn, the differential gears spin and power the blades. The blade is placed in a large stock watering tank to mix the material. A baffle on the side of the tank forces the slurry back into the blade as it circulates. With this mixer it has been possible to make three or four wheelbarrows full of thick papercrete in about twenty minutes.
Paperpulp may be added to clay soils where sand is not available. The added paperpulp helps to minimize cracking when the material dries.
As of 2007, papercrete lacks approval from the International Code Council. This limits its range of use within the city limits of most incorporated United States cities where building codes apply. It is not used as a load-bearing wall where building codes apply. However, its strength in model structures has been proven, and homes and small commercial buildings are being constructed. There is little or no evidence of its long-term durability at present.
Papercrete gets its name from the fact that most formulas use a mixture of water and cement with cellulose fiber. The fiber is usually acquired from recycled newspaper, lottery tickets and phone books. The mixture has the appearance and texture of oatmeal and is poured into forms and dried in the sun, much like the process for making adobe.
Dried papercrete has very low strength, but fails by slow compression (due to the large air content and hence compressability) rather than in a brittle manner. Concrete and wood are not known for their insulating qualities, however, papercrete also provides good insulation.
Its R-value is reported to be within 2.0 and 3.0 per inch; papercrete walls are typically 10 to 12 inches thick. Unlike concrete or adobe, papercrete blocks are lightweight, less than a third of the weight of a comparably-sized adobe brick. Papercrete is mold resistant and has utility as a sound-proofing material.
Research tests into papercrete have been carried out by Barry Fuller in Arizona and Zach Rabon in Texas. Fuller directs government-funded research on papercrete through the Arizona State University Ira A. Fulton School of Engineering. He is also head of a subcommittee for the American Society for Testing and Materials, and it is his goal to set standards that will lead to acceptance of the product within the architectural community and commercialization of the product, especially for affordable housing.
Structural tests have been completed on several papercrete formulas and Fuller claims the compressive strength of papercrete to be in the 140-160 lb./sq. inch range. A more useful measure of papercrete's properties is its stiffness - i.e. the extent to which it compresses under load. Its stiffness is many times less than that of concrete, but sufficient for the support of roof loads in some low-height buildings.
Dried, ready-to-use papercrete has a rough surface. This increases its surface area and provides a very strong bond from one block to the next.
Papercrete has also been tested for its tensile strength. Fuller notes that a papercrete block is the equivalent of hundred of pages of paper - almost like a catalog. Papercrete has very good shear strength as a block. Lateral load involves sideways force - the wind load on the entire area of an outside wall for example. Because papercrete walls are usually a minimum of twelve inches thick, and usually pinned with rebar, they may be strong laterally.
Zach Rabon founded Mason Greenstar in Mason, Texas for the purpose of producing and selling a commercially viable papercrete block. His product, Blox Building System, is at present the only mass-produced commercial papercrete block in the market. He has built several residential structures with it.
The Mason Greenstar block had its genesis in a journey Rabon's father, Kent Rabon, made to Marathon, Texas. The elder Rabon made the acquaintance of Clyde T. Curry, the proprietor of Eve's Garden Organic Bed & Breakfast and Ecology Resource Center.
Mr. Curry was an early proponent of papercrete and benefited from the lack of building regulations in the small mountain community of Marathon. Curry built four of the rooms at the bed and breakfast either partially or entirely out of papercrete and is in the process of building two more, in addition to a library and reception area, entirely out of papercrete.
Papercrete's ready moldability provides considerable flexibility in the designed shape of structures. Domed ceilings/roofs may be commonly constructed with this material.
Along with Fuller's work at Arizona State University, Curry's establishment has become a resource center for people interested in papercrete, and workshops are intermittently held there.
The Rabons had prior experience as homebuilders and are owners of a ready-mix cement plant in Mason. They have invested in research and testing on their product for several years. However, they consider their product a proprietary formula. They have filed for a separate patent even though a patent for papercrete had already been filed in 1928. The block developed by Mason Greenstar is known for its uniform shrinkage (all papercrete blocks go through a lengthy dry-time that involves some shrinkage), giving it a sharper edge.
Fuller has remarked that in tests he has performed on the Rabon block, it has outperformed other formulas.
Papercrete is claimed to have benefit of being a project that involves little cost to start. The materials are claimed to be cheap and widely available. Machinery suitable for small-scale construction is simple to design and construct.
When properly mixed and dried, the papercrete wall can be left exposed to the elements. In its natural state, it is a grey, fibrous-looking wall. For a more conventional look, stucco can be applied directly to it.
A study model home made of papercrete has been built at the Lyle Center for Regenerative Studies. This study model is a sample of homes to be built for a sustainable community in Tijuana by students of California State Polytechnic University, Pomona