| Building Green on Your Own, Part 4 |
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Papercrete This is a mixture of newspaper, sand, cement, and water. Paper is cut into small pieces and soaked for 24 to 48 hours, and then sand, cement, and water are added. Stir to a thick gray slurry that can be poured into block forms (like adobe forms) or directly into wall forms. It slowly dries and sets up into solid blocks with good thermal mass and good insulation. Set the blocks on the foundation in a running band pattern, mortared into place with wet papercrete slurry, and then plaster the exterior and interior surfaces. Fiber adobe is a variation that uses clay instead of cement as the binder. It dries slower, but is cheaper. Stone Stone must be laid on very sturdy foundations of stone or concrete, in a running bond pattern with cement mortar. The mortar holds the stacked stones in place and decreases air infiltration. Thick, uninsulated exterior stone walls work best in hot, arid climates. In cold climates, walls must be insulated. Disadvantages of working with stone include its weight, and the fact that the work is slow and boring. In seismic areas, steel reinforcement is required due to stone's low tensile strength. Also, stone is cold, and moisture often condenses on interior walls. Eliminating the problem requires double-wall construction or interior wall insulation. Slip-form stone buildings are built using slip forms-wooden forms placed squared and plumbed on a foundation. Selected stones are placed on the outer face of the form, one course at a time. Concrete is then poured into the form after each course to fill remaining space. Insulated Concrete Forms (ICFs) ICFs are hollow blocks of varying length made of rigid foam insulation (beadboardaka, expanded polystyrene). Used to build foundations and interior walls, they snap into place. When concrete is poured into them, manufacturers install plastic or steel cross-bridges that attach one side of the form to the other. The ICFs are left in place, and the foam sandwich produces a foundation or external wall with an R-35 insulation rating. See the glossary for an explanation of R-ratings. The advantages of ICFs are their light weight, ease of handling and cutting, good seismic performance, and insect and fire resistance. Hybrid Dwellings Most natural-material builders use more than one type of building material. Many times unusual materials are used to build unusual spaces, to fill nooks and crannies, or to make fireplaces, bookcases, or other specialty components. |
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