Building with Bamboo

At one point we did have to get out the really
heavy duty machinery... 

            Before I came to Hawaii, the word bamboo made me think of East Asian ink paintings or high-end cutting boards. Through Bobby’s hobby/passion/trade, I have a whole new understanding of the versatile building material.

            Bamboo is the fastest growing plant in the world with record growth rates at 24 inches per day. A time-lapse camera would almost be overkill! The huge grass grows in two distinct ways. There's temperate running bamboo, that can quickly take over a yard if not managed properly, and clumping bamboo. An established plant – at least four years old – can send up 10-25 shoots per year. A healthy clump should have 20-40 poles, meaning that the clumps require constant thinning.

Unfortunately, thinning bamboo is no simple task. Heavy-duty tools and several hours of intense physical labor are required, plus the knowledge of the proper way to harvest the material.

Many islanders have overgrown clumps of bamboo in their yards left by the last home-owner – who may not have considered what 24 inches per day would add up to over the years - and need guidance in maintaining it. When it comes to finding someone to help maintain a bamboo clump, word of mouth on this small Big Island leads to Bobby.

Last week we drove down the coast to Ed and Edi’s beautiful home and small-scale fruit and coffee farm. The couple’s 10-acre property contains upwards of 50 bamboo clumps desperately needing attention. Edi met Bobby at a bamboo workshop last year and requested his advice and assistance in evaluating the giant grasses on their property. Bobby needs bamboo for a new project – building an outdoor bamboo classroom at a high school on the island – and Ed and Edi were willing to trade the service of evaluation and expertise for some of the poles for the project.

We started with a ‘latiflorus', or Taiwan Giant, clump. Very overgrown clumps require pulling the poles out rather than attempting to push them over (timber-style) because the cluster of branches at the top hold the poles in place even after they’re cut at the base. Bobby cut the poles at their base with an electric saw and then I grabbed the base and ran away from the clump, tugging hard to detangle the top from the rest of the branches. Once the pole came free I ran and let go just as the top of the pole was about to hit the ground. We went through this process over and over and over. And over.

The poles are roughly 40-60 feet long, depending on the age. We kept the thickest, straightest poles to be used for the classroom, and dragged the rest into a pile to be chipped. Ed and Edi plan to put in 750 pineapple plants in the next few weeks and will need all the mulch they can get.

We worked all morning (with a break for Edi’s freshly squeezed orange/tangerine juice) and pulled about 40 poles from the clump. We had 15 usable poles for the project and minor scrapes and cuts – some varieties of bamboo have wicked thorns.

Before the poles can be used for building, they are pressurized in a tank containing boric acid for three and a half hours at 130 psi. This process essentially sucks out the sap and replaces it with salts to ‘petrify’ the bamboo. The poles have to dry for three to four weeks in a preferably breezy location after they are removed from the tank.

Ed's method of drying coffee beans in his greenhouse

Bobby will be working with a class of 20 high-schoolers to construct the outdoor structure over the semester. The kids have made scale models and some have had the opportunity to help Bobby with the harvesting. It’s pretty amazing to be able to see the raw building material actually alive, in the ground, and then follow the process all the way through to the construction of your own classroom. Experiential learning – for me and the students!