The easiest, strongest, cheapest, and most durable material for building structures may now come from your garden. A new book describes best practices, and a workshop is coming up shortly in Australia.
When architect Darrel DeBoer first encountered bamboo as a building material, he knew it was going to be revolutionary. He had a long history of researching and teaching about building with non-toxic materials, using renewable materials such as straw-bale for building, and creating innovative designs; and bamboo is proving to be a new tool to extend these areas into new, very exciting areas. Now he’s written a book packed with photographs of beautiful design ideas, and hints for working with bamboo that he’s learned from numerous projects around the globe.
A Great New (Old) Building Material
You may have already heard bamboo extolled as a wonderful building material. It’s strong as steel in tension, and stronger than concrete in compression. It’s cheap. It’s easy to work with because it’s so much more lightweight than wood, concrete, or steel; it has a huge strength to weight ratio advantage, mainly because of the hollowness of its cylinder shape.
It’s easily available, as a never-ending source — with one quarter of the grove harvestable each year. Unlike hardwood, you don’t need to wait for 75 years to get a crop. Using bamboo gives you control over your own source of building materials. Its availability is not subject to market prices, nor need it be produced far away from the building site, by people you don’t know. You can get it growing in the area of the house you want to build, and harvest just the amount you need, as you need it. Needless to say, there are projects considering the use of bamboo for building in many "third-world" countries.
And finally, it’s far less dangerous while building, plus it is far less dangerous in the case of a storm or earthquake destroying a building so badly that its building materials wind up falling on its inhabitants. But that is a rare situation with bamboo. Excitement about building with bamboo amplified when a 6.2 earthquake hit central Colombia in January 1999, and 70% of the recently-built concrete and brick buildings failed, while virtually all of the older village buildings, of bamboo, stood strong and un-damaged.
Problems Recently Solved
In the last 20 years two basic problems, of joinery, and of preservation, have been solved, allowing much more innovative building and moving bamboo forward as a "modern" building material.
The joints in earlier, non-engineered, bamboo buildings used to be lashed or pinned, and they would eventually come loose, as the seasons changed from wet to dry to wet again — the expansion and contraction loosened the joints.
New techniques now use bolts at the joints, followed by filling the area around the joints with the injection of a substance that becomes solid. The best material tested for this so far is mortar (made of 4 parts sand, 1 part each cement and lime). This keeps the bamboo from crushing when you put a load on it. So, if the building is properly designed, with lots of triangles, loads run along the axis of the bamboo.
As we know from the design of geodesic domes, in any building material, if the design uses a lot of triangles, when corners are fixed the structure can’t move (unlike squares which, like dominoes, can slide over and collapse). All pieces are in tension or compression, making a very strong structure. The result is no physical loss of strength at the joints, so the buildings are even stronger when facing hurricanes or earthquakes.
Applying the mortar is very simple. Drill a hole, put in the bolt; drill another hole, put fill in there.
The preservation problem has also recently been solved. The main problems are with fungus, and with powderpost beetles. It has been found that since the digestion process in beetles involves bacteria they can be affected by various salts. Especially effective is borax, which is harmless to humans; it is even used in, for example, Visine eye solution. So it is not dangerous for builders to work with.
Borax is also used as a fertilizer, as well as in mouse poisons, where it behaves similarly, infecting the bacteria in the mouse’s stomach. So it’s easy to buy in either of those preparations. To use in preserving bamboo, one only needs to combine the boric acid from either of those preparations in a 50/50 ratio with borax (from eg. Twenty Mule Team Laundry Detergent). Add water until the dry materials stop dissolving. (Another way to describe this is that you are creating a 5% solution.)
This preservative is then put into the interior of the bamboo, by drilling holes into every internode, then putting the drilled bamboos into a large bath of the solution. Or you can drill holes down the length of pole, then stand them up vertically and fill with solution. This should sit for a week, so that the solution diffuses through the pithier interior walls. Drain out the excess, and your bamboo is ready for use.
Another way to apply the preservative, especially good for shorter poles, is to stick them into, for example, a garbage can full of solution just after the bamboo has been harvested (and so still alive); the live cane will absorb the solution very thoroughly, because its processes are still sending liquid up through the capillaries. Using this technique, one can get the solution to rise up to 8-10 feet.
DeBoer, who is based in the San Francisco Bay area, has visited building projects in a dozen countries to learn more about the material and gather great examples for his recently-published book. Extraordinary bamboo structures by architects and designers such as Colombians Simz and Marcelo Villegas, German Joerg Stamm, Celina Llerena of Brazil, Bobby Manosa from the Phillipines and Jorge Moran in Ecuador, and others, are demonstrating to the local communities and world that bamboo is a beautiful material that even the wealthy are choosing for their houses and buildings.
Following the initial innovations of the first generation of engineered bamboo buildings, the second generation is just getting started. The really thoughtful work has just begun. It’s a very exciting time in the history of building. You can be part of this innovative experiment in several ways:
DeBoer will be teaching Bamboo Design and Construction Workshops, this coming April 2011, across four Australian states (NSW – QLD – WA – VIC). Sign up here.
Examples of DeBoer’s architectural and furniture design can be seen at: deboerarchitects.com
More on building with bamboo is online at: BambooBuildingEssentials.com
The new book, "Bamboo Building Essentials: The Eleven Basic Principles" by Darrel DeBoer and Megan Groth, is available through DeBoer’s website (also, he’ll have some available for workshop participants). Topics covered: Ways to Use Bamboo, Choosing Species, Growing, How to Harvest, Treatment and Curing, Splitting, Good Hat/Boots, Shear and Triangles, Joinery, and Bamboo and Building Codes, plus hundreds of photos.