Natural building is more than a set of techniques, it is a way of being and thinking. How do we build with materials that come from the landscape around us and can return to the soil when they are no longer needed? How do we make places to live and work that feel as if they belong where they stand? How do we shape our lives and our homes to fit more gracefully into the flow of give and take that is nature? These questions are at the root of the movement that has come to be known as Natural Building.
What is Cob?
Cob building uses hands and feet to form lumps of earth mixed with sand and straw, a sensory and aesthetic experience similar to sculpting with clay. Cob is easy to learn and inexpensive to build. Because there are no forms, ramming, cement or rectilinear bricks, cob lends itself to organic shapes: curved walls, arches and niches. Earth homes are cool in summer, warm in winter.
Cob has been used for millennia even in the harsh climates of coastal Britain. Thousands of comfortable and picturesque cob homes in England have been continuously occupied for many centuries and now command very high market values.
This ancient technology doesn’t contribute to deforestation, pollution or mining nor depend on manufactured materials or power tools. Earth is non-toxic and completely recyclable.
Read more about cob here: http://www.barefootbuilder.com/faq.html
What is Timber Framing?
Wooden posts (vertical members) and beams (horizontal carrying members) are connected together with pegged wooden joinery rather than bolts or other metal fasteners. This wooden joinery distinguishes the timber frame from other kinds of post-and-beam construction.
A timber frame can be cut entirely with hand tools and entirely of wood, making for a most natural process and product.
At Natural Cottage Project workshops, we may also teach Round Pole Framing. This kind of post and beam construction may use chalkline-leveled layouts and chiseled housings combined with modern screw fasteners, or it may use rope and twine lashings to fasten small logs and saplings together. Lashed pole and bamboo framing is traditional in both Scotland and China, and many other parts of the world besides.
What is Straw Bale Construction?
Straw bale walls are most often made by stacking bales like giant bricks, then coating the inside and outside surfaces with plaster made from clay, lime, or lime-cement. The bales and plaster together give the wall structural integrity, a high insulating value, excellent fire resistance, and protection from weather and critters.
Unlike hay, straw is not food: straws are the dried stems of cereal grains like wheat, rye, and oats after the grain has been removed, and are used on the farm for animal bedding or mulch. Plastered bale walls have passed the same fire safety tests as stud-and-drywall conventional walls. These walls are considered super-insulating, with insulation values of around R-30.
Properly designed and built, straw bale homes are well suited to cold, damp climates as well as hot dry ones. There are 20-year-old straw bale houses functioning well in Nova Scotia, Arizona, New England, and New York. The oldest straw bale houses – and a church – are in Nebraska, and were built over a century ago. There is even an early-twentieath-century straw bale home in hot and humid Alabama!
What is Straw-Clay?
Straw-clay, or “light clay-straw”, was developed in Germany during the nineteen thirties and forties. The German government supported research to create a building material that was cheap, easy to make, durable, and insulating. Starting with the centuries-old tradition of wattle-and-daub, experimenters increased the proportion of insulating straw while reducing the proportion of earth to a minimum and refining it to include only sticky clay. The result has worked well for over fifty years in the cool and damp climate of northern Europe. The clay acts as a drier, drawing any moisture out of the wall and protecting it from rot. Thus, while it is best to keep a straw-clay wall dry, it can be very resilient to wetting and humidity.
To make it, clay slip (a creamy mixture of clay and water) is poured over loose straw and stirred until each straw is lightly coated with the clay. The mixture is then packed into formwork to create a wall. Leap-frogging forms known as slip forms work well with straw-clay because the forms can be removed as soon as the mix is placed, moved up the wall, and filled again, over and over, allowing the builder to use very little wood for the forms.
Wet straw-clay needs plenty of air-flow on both sides of the wall to allow it to dry properly. Drying takes about a week per inch of wall thickness in moderate climates. The maximum recommended thickness for walls is twelve inches. Straw-clay can also be pre-dried and used to fill enclosed stud or joist cavities, as well as attic spaces, though using it in this way is very dusty work which requires a respirator.
Walls made of straw-clay are not as insulating as straw bale walls, but they can be made much thinner and easily formed into shapes that would be difficult to create with bales. For moderate climates, and for uses where there may be periods of high humidity, such as in a sauna or greenhouse, straw-clay walls can be an excellent choice.
What is Thatching?
Thatching is the process of creating a roof surface using plant material. Phragmites reed grass, a traditional thatching plant originally from Europe, is the material that we are using at Natural Cottage Project workshops and at the Strawbale Studio. Roofs made with reed thatch are long-lasting, insulative and very beautiful. Reed harvested in local fields and marshes are applied in layers, and held in place with sways (long wooden sticks harvested from the woods) which are literally sewn to the roof structure to secure the reed to the roof. The layers are applied in an overlapping fashion and tamped up to create a finely shingled effect. Rain transfers from reed to reed on the outer layer, and does not penetrate down into the roof. A ridge application, of reed or other natural materials, protects the top of the roof.
In the design of the roof it is important to have at least a 45 degree angle (12/12 pitch) so that the water flows quickly down the surface and off the roof. It is a slowly biodegrading roof expected to last 25 or more years, and re-thatching on top of the existing layer can continue to extend the life of the roof. Ridge applications need to be redone, or over-coated more frequently from 5 – 15 years depending on the plant material used, or a more enduring copper cap can be constructed. Thatched roofs are traditionally put on hip roofs and gable roofs.
Although this is an artful craft and a skill that can take many years to master, the basics can be understood and learned by beginners, and a successful and beautiful roof created. After learning the basics in a course, it would be recommended to start on a small structure to practice the process of harvesting, storing and application.