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Some Bamboo Do-It-Yourself Stuff
A word of caution: Please do not assume that all the bamboo you see growing will serve you well as construction material. Several details can make the difference between a completely successful bamboo construction and a very short lived disappointment. Five key elements to remember:
- The culm must be at least three years old
- The species should match the application
- The pole should be properly cured
- Design does make a difference
- Fasteners can make or break the product
Properly managed groves are marked the year they shoot and are not harvested until they are of age. Culms cut too soon are full of sugars, water, and quickly become soft and food for bugs.
Some bamboos are thick-walled and ideal for structures and posts, others are thin-walled and are outstanding for covering frames and pipes. Some bamboos have very hard wood and make excellent tools, others are tough and nailable with resistance to splitting, but will not take a finish. Some are waxy and some are nearly waxless. Check out species before you commit to the effort. A good reference book is The Book of Bamboo by David Farrelly. It is published by Sierra Club Books. Check out the American Bamboo Society source list for distributors of bamboo books.
There are several effective curing regimens for bamboo. The process sometimes includes soaking out the sugars and treatment with boron salts. The minimum treatment skips these steps and moves immediately to drying. Drying normally must be done in a controlled manner with lots of air circulation, a method to avoid having the culm take a curved set, and protection from cracking resulting from overexposure to direct sunlight on one side only.
Designs using bamboo can successfully work the material in compression on tension. Torsion is difficult. Successful applications usually treat the poles as if they were stiff members of a pinned structure. They are not like timbers capable of accepting a few nails to produce an acceptable cantilever.
Finally the fasteners are very important. Bamboo is round, usually hollow, slick-skinned, and splits longitudinally with ease. It is normally necessary to pre-drill all holes for screws. Nails will only work on a few species (though some green bamboo will take careful nailing). Bamboo will shrink as it dries. Take care that the drying does not produce a crack through the fastener or the joint will fail. I recommend that a relief cut be placed from end to end on each pole and the cut be oriented where it is not seen or where it becomes a part of the design. As the bamboo absorbs and rejects moisture, the relief split will open and close without cracking where you do not desire it to. There are several books on the subject of bamboo joining including The Book of Bamboo mentioned above.
Many of the books on Japanese gardening include drawings and photos of Japanese bamboo fences. If you are handy and pay attention to the caveats above you probably can put together the simpler attractive bamboo fences shown. One feature these fences usually have is a pattern of decorative knots. The material used is Coir line which is dyed black. A good long lasting substitute is black polypropylene line. However the latter line must be cut with a soldering gun or hot plastic line cutter and the knot must be fused with heat or it will spring apart.. I like to use a paint-stripping heat gun to fuse the knots. The knot itself has the bitter ends protruding in a close "V". A square knot looks quite bad in this application.
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