Paper Houses

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FOUNDATIONS

Although some papercrete houses have been built directly on rubble trench foundations, most recent builders, including Virginia and Andy, are using modest concrete foundations or stem walls. The weight of the heaviest papercrete building, even with a hefty snow load on the roof, is on the order of 5 psi. Since papercrete has a compressive strength in the 300 psi range, and concrete has a compressive strength of 3,000 psi, neither walls nor foundation are likely to come close to having their limits tested.

Andy's foundation is 12" wide, 8" high, and sits about 4" above grade. Virginia has a 12" wide by 10" high concrete stem wall resting on a rubble-filled trench. Both used horizontal rebar laid lengthwise to eliminate any possibility of the concrete cracking.

As with straw bale, papercrete builders have also started inserting into the foundation short pieces of vertical rebar on which to impale the first course of blocks. Again, it's important to use a stem wall or to build a foundation that peaks a few inches above ground level. It's also a good idea to paint the top of the foundation with concrete sealant to prevent wicking of moisture into the wall.

FLOORS

Since papercrete is a good insulator with high compressive strength, it is commonly used as a subfloor. First you lay down a sheet of plastic and make one-foot slits every few feet so that the excess slurry water can drain out. (Since the slits are so small, wicking of soil moisture back into the floor will be minimal.) Next, you pour a 6" layer of papercrete onto the plastic and allow it to dry. Finally, you cover this with a 2" layer of concrete or adobe. Since the papercrete has a certain amount of give to it, the resulting floor is slightly springy, like a wooden floor, and isn't as hard on the feet as solid concrete.

Another strategy is to make the floor totally out of papercrete. Using two bags of cement per batch will create a hard floor, which, when stained an attractive color and sealed, should stand up to considerably hard use.

WALLS

If building with blocks, you'll need to drill holes through the first course so they will slip over the vertical foundation rebar. Put down a 1" bed of papercrete or fidobe mortar onto the already sealed foundation, then slip the dried blocks into place. Subsequent courses are laid just like regular adobe, using papercrete or fidobe slurry as mortar. It's always a good idea to use string and a level, like adobe builders use, to keep your walls plumb.

Papercrete and fidobe can also be formed into "logs" measuring anywhere from 4' to 8' long. (It will take two people to move an 8' log, but the wall will go up very quickly.) The logs should be reinforced with cane, bamboo or small saplings, since the longest logs tend to break unless they're completely dry. Logs will give you a stronger wall than will blocks, as fewer mortar joints are required. Plus, a set of long logs extending out in each direction makes for a very strong corner. Logs can be easily cut with a chain saw to fit precisely between window frames. (Be sure the logs are totally dry before you cut, or you'll have to contend with shrinkage.)

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