Papercrete: The Starting Point for Very Low Cost Construction
What is Papercrete? It’s simply shredded newspaper, Portland cement and sand in somewhat variable proportions of 60/20/20. Papercrete is blended in a homemade drum mixer into a wet slurry, and poured into brick forms, or pumped into formworks to make walls. This building material has great potential because it is cheap, utilizing unwanted newspapers, magazines, cardboard and junk mail, plus local sand and dirt. Papercrete can be produced onsite, using few tools, and is easily handled by women, older folks, nonprofessional builders and anyone who wants to experiment freely.
The mix of recycled paper and cement isn’t entirely new. There have been test structures built in the past; one by a builder in Tucson, AZ, in 1983 who constructed a 12 foot diameter dome. His papercrete structure was an experimental dome covered with wire mesh, and 1î of papercrete slurry applied. That papercrete recipe was 50/50 cement and newspaper, by weight, with no sand. The dome, which weighs only 300 pounds, was coated inside and out with an elastomeric paint, and is still standing well after 15 years.
Papercrete is really an industrial form of paper mache. In construction use papercrete performs like adobe because it can be made into large or small bricks, or blocks. It can also be poured like cement, made into a monolithic wall, infilled between poles or studs like light-straw clay, shaped into large, reinforced panels; mortared, drilled, hammered, nailed, used as plaster, and more.
It is easy to use as cheap insulation in either pre-made blocks, or as wet infill between studs. It soaks up water like a sponge, but dries out again, so it must be protected from the elements like any natural wall material such as adobe, cob or straw bale. In a wet environment like the Pacific Northwest it is best to work in summer, or make pre-cast blocks so drying time is kept short.
Over the last twelve years, Mike McCain, an inventor/ builder located in Colorado experimented with shredded recycled paper, sandy dirt and cement to produce an amazing product he calls fibrous cement. Eric Patterson, a printer by trade in New Mexico, developed and patented Padobe over six years ago, from just newspaper and cement A third force in papercrete advancement is Sean Sands, a retired physician who is experimenting with earth sheltered papercrete structures. Sean and Mike constructed experimental domes at a community in New Mexico in 1998, and both are continuing to build. Mike now lives in northern Mexico and is actively teaching, experimenting, and building ultra low cost housing to help the poverty stricken people there.
Eric started out by looking for a way to recycle all the waste paper from his print shop business. He has experimented with various amounts of cement and paper, and now uses a 2 pound coffee can full of cement per 55 gallon drum of paper and water. His initial results were so good he built a privacy wall, added a room onto his house, and constructed a dome shaped guest house in the backyard. Eric says that Padobe walls won’t crack, can be pounded with a hammer and only leave a small dent, and won’t leach heat out of the house. Also this material will hold a screw or nail well. Eric compares the insulation performance of his material to Fiberglas, explaining that a 12î thick Padobe wall should offer close to R36 (this has not be officially verified). A view of his walls, painted white with regular latex paint, look no different than any other standard wallboard.
Mike McCain is a true inventor, he’s built domes with blocks, and used a slipform to pump slurry to create a monolithic wall. He’s invented dragforms to make many blocks at once; designed efficient mixers, easy to use adobetype block makers, and many other aids to small scale production. Mike says the material can be made as soupy as you want, and that excess water will drain out easily, and that the mix can’t be over saturated. Mike will add one or two 94 pound sacks of Portland cement to his stock tank mixer (4’wide x 3’ tall), plus sandy dirt, newspapers, pizza boxes, old phone books, magazines, and junk mail. Mike loves papercrete because there is no one ‘right way’ to make it, and it is a very forgiving material to produce.
How Papercrete is Made
It’s easier to experiment with papercrete if you can make test batches with simple kitchen equipment, before moving on to build a mixer for larger scale production. I call this Kitchencrete, and the whole family can join in. If you have a blender or a food processor (or buy a used one at a thrift shop) you can shred newspaper and make slurry. A hand mixer won’t work, so use a blender. First soak several sheets of newspaper (don’t use office or magazine paper yet, it won’t pulp well), use disposable plastic tubs or bowls and pre-measure, by weight, the wet paper, sand and cement. You can eliminate the sand/dirt if you want. Then place a cup of water into the mixer, add several wads of newspaper and grind. After you have a pulped all the paper into a gray mass, add the cement and grind for a few minutes, adding water as needed. If you don’t want to put cement in your blender then hand mix it with the pulp in a separate bowl. Turn the mass onto an old window screen and let drain for 30 minutes. While wearing vinyl gloves scoop up the papercrete and place it into a small cardboard box to dry, or shape into squares, or patties and let dry on the screen overnight. Any excess water will evaporate, and in a few days, depending on sunlight and air circulation the bricks will dry hard and very lightweight. While you can’t make too much papercrete in a day with the blender before it will overheat, you will make enough to shape bricks, or hand sculpt a small model. Play with the material a lot, go find different sands, and very clayey dirt ( no topsoil) and experiment. Using small cardboard boxes lets you experiment inexpensively; peel off the cardboard after a few days and let the brick keep drying. Cracking can be eliminated with more sand, but shrinkage will occur. You can also use a recycled newspaper insulation material called cellulose. The finely ground newspaper is like cotton candy, and sucks up water like crazy, but it will drain out while drying. A bale of locally made cellulose costs about $12. and provides a way to experiment with no blender, just hand mix the cement and sand in. [If you want to make insulation just use the celluse as is, but it needs to be ‘blown in’ to wall cavities, with a commercial machine.] The tensile strength with just cellulose will be poor, so add dry grass clippings, or chopped straw to add fiber.
As you can see papercrete can evolve into other mixtures. Personally I am now mixing everything but paper and cement in my experiments. I use harvested clay, bagged hydrated lime, Redwood sawdust and other local materials to make what I call Cobwood. Papercrete was developed in a desert area without trees using waste paper, so you can experiment with indigenous or recycled materials where you are. The advantage of redwood sawdust it is it pre-chopped, won’t mold or rot, is available locally in Humboldt county.
The primary block for most people is building a mixer to grind the recycled waste paper into slurry. A homemade barrel mixer with sharp lawnmower blades or S shaped blades as developed by Mike and Eric are difficult to construct, cost about $300, and don’t always work. Cement and mortar mixers also can work to mix, but not chop because they can’t pulverize the paper well enough. The easiest method is to obtain shredded or cross shredded paper, then a cement mixer can be used for a ‘rougher’ type of papercrete. Functional use can be made of a household garbage disposal but they overheat quickly. Wood chipper/shredders seem to work but sometimes don’t shred paper well enough. The best invention to date is Mike’s ìThird World Mixerî a towable stock tank mounted on a welded framework, with car tires. This mixer uses an axel and auto differential to turn the attached 18î lawnmower blade and chop the paper. When towed by a slow moving car (5 mph) or even an animal, the tires turn the blade which chops the paper into a slurry. No electricity is needed, or gasoline for the mixer itself. Towing the water and paper filled tank a few blocks makes perfect papercrete slurry says author Gordon Solberg, who watched Mike’s mixer in action.
Mixes of 50/50 newspaper and cement make a strong exterior stucco layer to cover papercrete bricks and other wall materials such earth bags or adobe bricks. On interior walls papercrete plaster can be left highly textured, or trowelled into a pattern, then painted. Papercrete dries to a pale gray color, and clay coated papers from magazines and glossy flyers aid in binding everything together. The advantage of making a plaster is you can cver any type of wall surface: plywood, OSB, old dry wall, Roughing up the surface is necessary, or adding fiber mesh tape to the wall first will help adhere the plaster. Adding more lime to the mix will also make it stickier.
Papercrete does have drawbacks, and since it is still experimental with only a few dozen private homes built. But there is a commercial effort by some to produce blocks in quantity for resale ( mostly in the south west) and some are testing and codifying the mixtures and use of this material. Look at the website www.livinginpaper.com for a good deal of recent information. There are reports you can purchase there too. The long term (20 year) performance results aren’t known. Now in 2012 papercrete building have been around for more than 14 years, and are doing well if protected from the elements.
There are concerns about its ability to withstand fire (due to accidental application of hot metal slag which slow burned and reduced a test brick to ash overnight), although direct flame contact produced only charring and no burn. And, no extensive insulation tests have been performed; plus papercrete blocks soak up water like a sponge (but releases it again) so they must be protected from moisture and weather. All that being said, it still has enormous potential as an ultra low cost building material.
What papercrete offers is freedom and personal empowerment. Because of cheapness, and ease of testing, from the kitchen blender level up to a full tank mixer, the average person is able to attempt very low cost designs. There is also the freedom to create economic shelters as alternative, acceptable housing. Many people may willingly choose to live in a papercrete structure while building a ‘real’ house, or to save income on shelter in general. Minimalists, environmentalists, and survivalists may prefer this type of building. Beyond that, creating low cost sheds, barns, animal shelters and storage structures is possible too.
There is social and community benefit. Using papercrete to build mother-in-law cottages, guest or teen quarters, allows everyone to have affordable housing. Every community needs housing for all its citizens, and this building material may prove a viable alternative. There is a great deal of potential to use recycled, free materials to make a variety of papercrete mixes, each having potential strengths and weaknesses. I encourage you to experiment and test small batches to discover what works. The emphasis is to build with non-toxic ingredients (no used motor oil for instance) with the goal of creating a strong, load-bearing, fire resistant, wet/rot resistant, insulative material.
The web offers many free resources. Do a search for papercrete, and look at www.youtube.com for dozens of video clips on the making and use of papercrete. A similar mix called Paracrete, utilizes waste polystyrene particles (Styrofoam), cement and sand, but no paper. The possibilities are unlimited. Since most people are inventing, and building independently there is no central information source. The best sites for information are www.papercrete,com and www.livinginpaper.com , along with books and DVDs for sale online. However you can experiment on your own first with all the free resources the internet provides.
Note: I wrote this original article in 1999, and have updated this version.
© 2012 C.R. Visnesky lives in a little green cottage in
Humboldt County, CA where she writes, and experiments with alternative
building materials such earth, lime, papercrete and more.