$300 Papercrete Pad
This concept for a $300 home is a simple shed roof style box home. I chose this because it does not take an engineering degree to construct it. The major material is papercrete, which can be used as blocks or slip form poured. Most of the materials can be found in most local areas and very inexpensively if not free: recycled paper, sand, concrete. Other materials can be used in the formula as well that may be strictly local � pumice, fly ash (that byproduct from coal plants), rice hull ash, clay, etc. This material is long lasting if used properly and is very energy efficient with a very high R-value. Now that I have your attention, let�s get into some details.
Papercrete (PC) is not paper mache. Think cob or adobe. These have been used in house construction for 100�s if not 1000�s of years. Papercrete is just the new kid on the block. (or should I say �in the block�) And with any material, one must consider where it is being used environment-wise, dry, wet, hot or cold and handled appropriately. In general, the paper makes the material light weight, and is what makes it a better insulator than just concrete blocks. 12� thick block with ½� stucco has about an R-value of 30. And the concrete makes it sturdy and stable and long lasting. In areas of high moisture, the PC can be coated with ½� of stucco on the outside and if desired or needed on the inside as well. This material is light weight enough to be used for the ceiling/roofing material as well. No sense in all that R-value in the walls, just to have everything go out a substandard roof.
My house design is an external 10� x 10� with 1� walls, leaving an 8� x 8� living area. The load bearing properties of PC is not exactly known, so I am supporting the roof using a post and beam construction and using the PC walls as in-fill. The post can be wood or recycled pvc or metal channels, posts, anything sturdy and long lasting. (a variation would be either putting the post into the wall or external as a porch post. And beams can be 2x6, 4x4, small diameter logs, bamboo, etc.
The foundation footing is critical especially in a wet area. The footing must be dug down to the frost line in cold areas. For the footing, you can use tires packed with dirt and offset like bricks. Or you can use rubble and gravel, using the larger material in the bottom and going to smaller gravel as you move up the footing, tamping as you go. Above that will be the stem wall made of sand bags filled with an equal amount of sand or gravel per bag. This is critical in that any dirt or most any other material will allow moisture to wick up from the ground to the PC. The moisture can cause mold to form. Sand does not wick moisture. Don�t forget the rebar. I would think it easier to stand the rebar first (pounding it into the ground some) and put the footing and stem material around it (tamping as you go). The rebar will protrude from the top of the stem wall for the PC to attach to. Now this home isn�t going anywhere easily.
The walls can be made from blocks or a slip form can be used to pour the walls in layers. It was recommended to do slip walls and not to pour an entire wall as that causes folding, uneven drying and some other things. If using blocks, use the PC for joining them together. It is best to frame out doors and windows as the walls are going up. But they can be cut out with a chainsaw later. (hell on a blade though)
To build the PC roof, I used a slight pitch 1:12, but you can increase it to 4:12. Have the beams about 24� apart. Stretch chicken wire across the roof. Stretch a second piece of chicken wire across the roof, but ½� off from the first piece. Spread a thin layer of PC on the chicken wire and allow to dry. Make the panels on the ground 2� x 4�. Fill the mold up to ½� from the top, put chicken wire on top then add remaining ½� PC and smooth out and set to dry. Add another thin layer of PC to the roof when you are ready to put the panels on the roof. This will mortar the panels to the roof. Counter sink screws into the panels into the beams. The second layer can now be poured on (if not too steep).
A stucco can be used to waterproof the roof, walls and what the heck, sandbags too. Or if you live in a very wet area, you may want to stucco the walls but put a metal roof over the PC roof. But allow the PC to breath to allow any possible leaks to air out.
The stucco can be made of Portland cement, slick lime, masonry sand and water
Now let�s transition inside the space.
Any window or door frames, shelves or cabinets should be screwed into the PC. Do not use nails as they will not stay in.
I have added some features that I feel are important for a healthy life. I feel that having some access to water for washing food and hands when preparing food is important for good health. So I included a water container to catch the water off the roof and when that container gets to full, it will flow off to the shared cistern or well. There is a simple hose that goes into the home and to a dry sink. A bucket is below the sink to catch the water.
The other problem in most poor housing is that the wood cook stove produces so much smoke in the house to cause a health problem to those in the house. It also is a great waster of the wood resources in the area. I have included a simple stove that can be made locally and inexpensively (under $10). It is called a rocket stove and uses a small amount of wood to cook with and emits very little smoke. I feel with as insulated as this space is, this cook stove can also be used to add heat into the space. I have also added a chimney and a stone hearth for the stove to set on. Here are the instructions on how to build the stove.
The bed is actually 3 cubes that can be tied or clipped together. During the day the bedding can be stored in the cubes and the individual cubes used for seating or tables, or stacked to be more out of the way.
A second bed can be attached with stout lines or chains to the ceiling beams, above the cube bed. During the day, disconnect two supports and allow the bed frame to fold down against the wall and be out of the way. Again, the bedding goes in the cubes of the bottom bed.
Stuff you will need to build this home
A typical starting formula for a 200-gallon batch is 160 gallons (727 liters) of water, 60 pounds (27 kilograms) of paper, 1 bag or 94 pounds (43 kilograms) of Portland cement and 15 shovelfuls or 65 pounds (29 kilograms) of sand. The sand adds thermal mass, reduces flammability and shrinkage, and packs down the slurry for a denser, stronger block. I have mentioned above some of the other things you can add besides sand. You will need about 30 batches to build this home.
Chicken wire for the ceiling � 200 square feet
Rebar qty 12 � 5-6 feet length
6 beams for roof 14-16 feet long
4 post for corners 2- 10 feet, 2- 8 feet
2 beams across front and back for other beam supports 10 feet long
Metal roofing � 100 sq. ft. (if required)
I don�t know much about the characteristics of bamboo, but if that is used in the ceiling, I could see it being used to replace the 6 16� lengths, but using more, perhaps only 1 foot spacing between them and perhaps one or two additional supports of bamboo beneath them midway from front to back and tied to each other to keep the swag out of the material and the roof.
For tropical or very wet areas, air flow needs to be increased. The structure should be raised up . The roof would be made of palm, grass or the other typical tropical plant type roofs instead of papercrete, with an increased pitch (hip roof) and increase eaves on all sides to keep rain off the walls. Also, since the structure is post and beam and the walls are not load bearing, the walls would stop about 6 inches from the roof line and screen material would bridge that gap, allowing air to flow across the top. The walls would be stucco'd inside and out to keep moisture out of the walls. The increased airflow would help discourage mold growth.
Roofing modification for Snow: If the home is in a snowy area, it will need to be sloped more or if increasing to over 4:12 then go to a gable roof. The insulation properties of the PC would be attached to the ceiling - flat, and metal roof would be gabled.