Bamboo Bridge

Our bamboo bridge overlooks an inlet to a spring fed pond . I wanted to use natural materials and we were developing a bamboo collection on the property. The clients had seen a bamboo bridge in a magazine article that caught their interest. So we set out to make one.

The bamboo bridge spans 17 feet. The timber bamboo I found varies from 3" down to 1.5" in thickness. I cut 3 year old canes and seasoned them in a shady garage for 3 months. The younger bamboo canes I cut were much weaker and seemed to have a lot less actual "wood". So I had to throw the younger material away. I took bundles of 3 bamboo sticks and lashed them together. There are three of these bundles that run the length of the bamboo bridge. Then I laid 3-4 foot lengths of bamboo as planking. I left a little bit of bamboo wood beyond each joint where I made a cut, as that material beyond the joints tends to split readily. I made a footing for either end of the bridge out of treated landscape timbers. This has stabilized the ends of the bridge. And it allows the bridge to slide a bit when people walk on it. When I first set the bridge in place and tested it I realized the bamboo bridge was still a little too bouncy. I lashed additional runners onto the top. This stiffened the bridge enough that it holds a couple of hefty guys quite nicely. I eventually put a handrail up for safety. I have repeatedly painted the upper deck with linseed oil. As it aged the linseed oil blackened the bamboo and the string. For the string I used nylon string that is usually used for string-lines on construction sites. The string tended to fray which made the knotting a little difficult but with the linseed oil the string has stiffened and none of the knots have loosened. It has now been 6 years since the bridge was constructed. All of the pieces are still intact and looking strong.

The bamboo bridge has required some regular maintenance but this has not been excessively time consuming. The cord has darkened considerably with each successive oiling of the bridge. I have been coating the bamboo bridge with linseed oil about every 3 months to keep the bamboo from splitting. Cracks open up with the summer heat but quickly close again as it rains, or as the oil soaks into the bamboo. My respect for bamboo as a building material continues to grow as this bridge keeps being servicable.