Natural Building
Natural Building is a term often used to describe a more resource efficient, ecologically sound form of construction. In the book Alternative Construction:Contemporary Natural Building Methods edited by Lynne Elizabeth and Casssandra Adams Natural Building is defined by not just the technique and materials used but by a set of ethics and a broader movement emphasizing a deeper connection to the earth as a living system into which we must integrate our built environment. Natural Building methods include the traditional and contemporary earth-based and straw-based techniques (e.g. adobe, cob,rammed earth, straw bale), timber framing, stone masonry and various other indigenous forms. Another important aspect of Natural Building is using locally sourced, reused and recycled, and less energy intensive materials whenever possible.
As an ecology center we feel strongly that promoting and facilitating Natural Building Projects furthers our mission to reconnect communities to their local ecosystems and land base. We are constantly on the lookout for usable, often discarded, resources to create Natural Building projects in schools, homes and community spaces. These projects can then serve as community workshops open to anyone who wants to learn more about natural building, share their knowledge with others or just participate in a natural community building project.
Below are some photos of recent and ongoing natural building workshops:
JEFFERSON ELEMENTARY SCHOOL - COB FISH (or WHALE depending on what you see) BENCH
(L) Cob, a mixture of clay, sand, and straw is best suited to a site that has plenty of sticky clay available. San Francisco, with it’s fabled beach sand is not always considered a great location for clay, but as you can see a building excavation site is a great place to get some clay and it’s free, all you have to do is ask. (R) A good cob mix is typically 15-25% clay to 75-85% sand/aggregate, although it can vary depending on the clay content of your subsoil. Here a mix is piled up to be stomped at a cob bench site at Jefferson Elementary School.
(L) 4th and 5th grade students at Jefferson Elementary school spend about an hour each week in a cob building workshop, leaving something behind for future students to admire and rest upon. (R) Tori teaches the students to press into the cob mix with their fingertips to get as much air out as possible while will strengthen the bench and prevent the clay from cracking.
(L) It is important when preparing for an earthen plaster to sift your clay and sand through a 1/4 inch or smaller mesh screen so only the fine particles remain. (R) Nico Morris, potter and natural builder, is showing us the finer aspects of earthen plasters with human hair as a reinforcement fiber, taking the place of finely chopped straw which is typically used in earthen plasters. Here we have to separate the hair (which was happily donated by some local high-brow saloons) as much as possible.
(L) Davin working with the students applying a second layer of earthen plaster, which is just very well sifted clay and sand and small fibers, in this case, human hair. (R) The finished product, if you look carefully, has little hairs coming out of it.
(L) The students placed tumbled pieces of recycled glass into the cob as a mosaic. (R) The artwork is finished, now it needs several coating layers of linseed oil.
WEST PORTAL ELEMENTARY SCHOOL - COB PANTHER BENCH
(L) This is how you make a quick cob bench on asphalt or concrete. First outline your design as Sharon does here with chalk. (R) Layout your urbanite base with more aesthetically pleasing stones on the outside edge.
(L) After a few well placed, dry stacked pieces of urbanite are in place you’re readying to add an initial layer of cob. (R) What you see in this photo was all done with less than a dozen helpers in less than 4 hours, from start to finish.
(L) The art of the cob stomp. Here, 4th and 5th grade students are taking turns busting moves on the tarp, making sure each strand of long fibered straw is covered in the clay-sand mix. (R) This finished cob layer is waiting for plaster and sculpting.
(L) Cob is easy to sculpt with. You can either build it up and out with embedded reinforcement like cob corbells or pieces of bamboo, or you can easily carve away from what you have already made. Here Tori is defining the face of a panther into the cob while Sam is building out some back legs. (R) Applying an earthen plaster of sifted sand, clay, and human hair is completely harmless and non-toxic, as opposed to working with lime and Portland cement mixes, typical of our modern building industry. The beauty is that people of all ages and abilities can work together on a cob job site; here you see 1st grader’s eagerly applying an initial plaster layer to the panther.
(L) You can easily add pigments into a finish plaster such as this iron oxide black that will give our panther a more natural color. (R) One the last plaster layer has dried and the surface is smoothed, shaped, and sanded to an ideal finish, you can apply Boiled Linseed Oil (BLO) as a weather resistant sealant. It’s best done in 4 thin but thorough applications starting with 100% BLO, than substituting 25% (then 50%, and finally 75%) of the BLO with terpentine or citrus solvent to help the BLO penetrate the surface which will be harder as each subsequent layer of BLO dries.
(L) The mosaic eyes and claws come shine once the plaster is rubbed off. (R) The BLO will dry to a matte finish. The more you add, the more it shines.
MONROE ELEMENTARY SCHOOL - COB CLASSROOM
(L) In preparation for building a larger circular bench situated at the end of the slope we have to first clear out the existing vegetation and all of the organic matter. (R) The subsoil at Monroe’s site is not ideal for making cob, but it is great for making earth bags - another form of natural building that incorporates the efficiency of on-site resources. Here you can see how family teamwork makes earth bag filling more fun!
(L) After the foundation trench is dug out, in this case about 30 inches wide (24 inches thick for the bench and 3 inches on either side for better drainage for the slope of the garden), and sloping from about 9 inches in the front to 15 inches in the back so the water runs towards another drain trench that is about 18 inches deep which we will fill with clumping bamboo to absorb any excess water that runs through the rubble trench foundation. (R) Once the rubble trench is filled in around the sleeved 4″ perforated drainage pipe, it should be tamped in place.
(L) Dozens (and dozens) of chunks of urbanite, the broken up pieces of city sidewalk and a great reusable building material, are used to lay the plinth (foundation or base course). A lot of hands in a line make quick work of moving it roughly into place. (R) Setting the foundation in with 3/8th inch roof gravel makes working with urbanite a lot easier and no need for mortar.
(L) Once our foundation was complete we were able to bring in our urbanite stack for the bulk of the bench, three chunks high. (R) The first official cob stomp to apply to the bench.
(L) Parents at Monroe applying the first layer of cob to the bench. (R) The cob drys best and leaves a key for the next layer to be applied by leaving a pock marked finish.
(L) A happy clay pulverizing crew. Once the dry, hard, clay chunks are busted in a bucket with a sledge hammer, they are poured through a 1/4″ metal screen to remove rocks and other unwanted debris. (R) The Urban Permaculture Guild’s PDC class came out to Monroe one day to help us out and learn about cob. We quickly put them to work helping move the last of our urbanite that was happily dropped off in front of the school by San Francisco’s Department of Public Works.
(L) The Urban Permies were hard at work with the help of PDC instructor Kat Steele and guest natural building professionals Marisha Harnsworth and Kevin Rowell of The Natural Builders. (R) After a hard (or easy depending on how you look at it) day’s work, our cob classroom has taken shape quite nicely. Halfway there, why don’t you help us finish it?
More photos to come as these projects and more continue!