Bamboo: A remarkable building material

Bamboo is as tough as steel, sturdier than concrete and can be harvested after only a year of growth. It is an ideal building material and now after much research, innovative new uses are being found to incorporate bamboo into North American housing.

What gives bamboo its super-strength? Looking at a cross section of the culm (the hollow stem) reveals countless tiny black spots. These are the cellulose fibres which run the length of the culm carrying nutrients between the leaves and roots. The rest of the stem is the lighter-coloured lignin. Individually, the cellulose is the stronger of the two components. Bamboo has been compared to reinforced concrete: the lignin would be concrete and the cellulose fibres the steel bars. Separately, the concrete may crumble or the bars may buckle but together they create a synergism, or combined strength greater than the sum of the parts.

Researches have discovered that ounce for ounce bamboo is stronger than wood, brick, and concrete by doing compression and tensile strength tests. They found that a short straight column of bamboo with a top surface area of 10 square centimetres could support an 11,000-pound elephant! (Hypothetically of course!)

This graceful plant with a lustrous yellow stalk and swaying foliage is typically associated more with Chinese paintings or peaceful garden pathways than a construction site. However, bamboo has been used for centuries to build affordable housing in New Guinea, Thailand, Columbia, and Bangladesh where it is an indigenous plant. Recent studies have revealed just how strong this plant fibre is and how useful it can be in creating safe, inexpensive building materials. The fact that it is also a quickly renewable resource makes it particularly attractive for resource-poor countries.

The National Bamboo Project in Costa Rica in 1987 was the largest and most successful government directed bamboo housing project to date. Seven hundred hectares of bamboo plantations were planted. Local builders were trained and helped construct 700 low cost homes at a mere $4,500 apiece. That project was so successful that by 1994 it was estimated 1,000 new bamboo homes would be built annually.

Those homes also underwent an unplanned stress test. In April 1991 an earthquake with a magnitude of 7.5 struck Costa Rica. Twenty bamboo houses stood at the quake's epicentre. Many of the concrete homes and hotels around them had collapsed but all 20 houses remained intact. One reason may be the light weight of bamboo. If you remember your physics from high school, force equals mass times acceleration so it is easy to see that a larger mass magnifies the force, which in this case, was an earthquake.

The low cost of this housing stems from bamboo's extremely low cost of production. Bamboo grows amazingly quickly-up to three feet (one metre) per year. While a pine tree needs at least 20 years to reach a marketable size, bamboo can be harvested after one year. The harvesting process is also much simpler-a machete or hacksaw is all that's required-and sawmills are unnecessary.

Building entire homes from bamboo is impractical in the North American climate however, great new products are available for specific applications. Bamboo flooring is one of the best innovations and it's becoming more widely available for homebuilders. The striking straw hues with specks of black are an attractive alternative to hardwood flooring. It's less expensive than hardwood and of course very durable. The strong fibres are also made into plywood and fencing. That old standby-bamboo furniture, remains a tasteful tropical choice for patio furniture or sunrooms.

There are a few drawbacks to bamboo however: it is not fireproof and it must be treated with preservative to deter termites. If the walls remain wet without air circulation to dry them they will rot fairly quickly. A large roof overhang is essential to protect walls.

This strong, inexpensive plant may help augment diminishing natural resources or timber. It can also provide emergency shelter in the wake of disasters. Bamboo may never replace concrete or wood entirely, but chances are it will become a standard part of housing in the future.

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