Laying a Rubble Trench Foundation While working out the design plans for the communal kitchen and adjacent space, I was able to contribute a few key concepts in sustainable design: a rain-water catchment system incorporating the existing aqua-duct, grey-water drainage leading from the kitchen sink to storage for the many gardens Karin has created, and natural light and heating by way of clerestory windows in the south-facing wall. Another thing I theorized was building the fire stove out of cob, continuing the sides into cob benches with a space left in the center of each, vented to the outside of the wall. It was my hope that the heat would pass through warming the benches. Cob is an excellent material for thermal mass, a characteristic which allows a space to maintain a more comfortable average in temperature fluctuations. Ultimately, we couldn’t confirm whether the movement of convection heat would work in the proposed system, or what shape would. I’d appreciate any feedback someone might have on this. Instead, they plan incorporate the cob benches separate from a regular fire stove. The structure will follow a 7 meter length along the (very wide) agua-duct wall, coming out to a 3 meter width. The aguaduct-side wall will be 30 cm shorter than the north-side wall, to allow both for rain water to run into the aqua-duct, and for water tubes on the roof to be heated by the direct sun of the south-facing-slope. The clerestory windows, which might make up for the loss of south-facing heat and light, will be set between the top of the agua-duct wall and the ceiling. The agua-duct wall will serve as the south wall. Once cleared of its brambles and loose soil, though, it was discovered that it is not the stone-built wall it appeared to be. In order to paint the existing wall with waterproof “Goucho,” we first needed to apply a layer of concrete to the loose soil: Using a concrete-mixer, we mixed 6 parts sand to 1 part concrete, then added enough water to make the consistency of thick dough. After measuring and tying string to mark the layout, the trench was dug 60 cm wide and at a 40 cm depth to reach below the frost line. Th line of rocks denote the inside wall which, in this case, will sit flush with the inside edge of the trench. Academically speaking, the wall sits on the approximate center of the trench; I’m not sure what difference this will make. Leah (left) is painting the aqua-duct wall with waterproofing Goucho, Karin (right) is digging out the last of the trench, and Linda (center), after tamping down the bottom of the trench, is breaking apart old bricks and tiles to fill the trench with rubble –in place of large gravel - also tamped down then roughly leveled. In this case, there’s been no drainage-pipe built into the trench to carry the house drippings away. It was said that this is not needed. A waterproofing plastic layer was laid on top of the rubble, and a concrete slab on top on that – again roughly leveled. Where the sink will go: Karin left a space in the rubble then set in a square of concrete block. An L-shaped length of PVC, joined by a PVC elbow joint adhered with a special, quick setting PVC glue, was set in the concrete block and packed with sand. The outgoing opening, currently capped with a sock, will eventually lead out through its own trench, at a 1 cm decline for every 1 meter run. Using biologically healthy soap, this will be grey water that can be stored and re-used in the gardens. While the concrete slab is still drying, the first concrete blocks were laid out according to exacting measurements – located at each north-side corner, and on either side of where the doors and their frames will go, with one extra placed beneath a point where the roof beam is jointed. Each first block was leveled on all sides to themselves and to each other. With this, the foundation is complete. Natural Building: Abroad Saturday, April 19, 2008 “Feierabend-bier” (“End-of-work-day-beer” with Linda, Karin, Carola, Sonja (all from Germany), and Leah (from England/Ireland).