Hawai’i and other tropical areas of the world have one of the world’s most versatile plants at their disposal: Bamboo. Much is misunderstood about the plant and how it can be applied for use as a building material in Western Countries, but in spots such as Southeast Asia and Latin America, Bamboo gets the recognition it most deserves.
Much of the confusion centers around how to properly treat bamboo. Once harvested, bamboo must be treated by either Salt Water bath, injecting the stalks with borax/boric acid solution, or heat treating. Once treated, the bamboo must be left to properly dry and cure. If these steps are taken, bamboo can last just as long as any conventional stick frame home.
I have come across too many people in Hawai’i who just pass off bamboo as a hard to work with material that doesn’t last very long. Milled lumber doesn’t last long either if it’s left untreated. Bamboo is no different.
Related: When working with bamboo, no matter whether you are building a house or making an instrument, a good machete is a necessary tool. I like the shape of a Billhook Sickle Machete because it can chop and carve holes in the bamboo. A must have tool.
Brief Description of Bamboo
Bamboo is an important plant in many cultures. In Japan, bamboo is not just a plant but an unspoken symbol of a nation.
While we tend to use bamboo for building projects, it is quite different from wood. Bamboo belongs to the family of grasses. There are over 1500 species of bamboo worldwide. Bamboo is hollow, has no growth rings, and does not increase in diameter as the plant gets older.
There are two main types of bamboo, running bamboo and clumping bamboo. Running bamboo is the type of bamboo that most people complain about. It can get pretty invasive. Running bamboo works well for furniture, decorative work, or as non load bearing lumber in construction.
Clumping bamboo tends to form tight clumps. It does not spread and become a nuisance like running bamboo. There are many types of clumping bamboo. Depending on the type it can be used for High Grade construction lumber, for furniture and so much more.
Bamboo is also known to be a very fast growing plant. It can grow as much as 10” in a single day. However, it takes up to 3-5 years for stems to be ready to harvest.
Because of its quick rate of growth, bamboo is a superior alternative to wood products. It can stabilize water ways, builds soil very quickly and can heal neglected soils. It has the ability to be regenerative to the ecosystem, as opposed to degenerative as are trees grown for lumber.
How Long Does Bamboo Last
This is where there can be a lot of misinformation. Most people I come across in Hawai’i believe bamboo is a crap material that doesn’t last long. And that’s true. If bamboo is used without curing or preserving, pests flock to it.
Bamboo is high in sugars that insects love to eat up and left without proper preservation it will last only a few years.
However, a properly harvested and cured stem of bamboo, left out of the sun and rain, can last upwards of 50 years, with some bamboo buildings lasting over 100 years!! There is a bamboo house in Vietnam that has lasted as long.
Nobody ever believes me when I tell them that.
Why Does Bamboo Weather
Like any natural material, bamboo is prone to weathering. The sun can cause a breakdown in the cellulose layer. The constant humidifying then drying of bamboo can cause cracking. Wind and dust will cause a sandblasting effect on the bamboo.
Weathering can be minimized if bamboo is allowed to stay out of direct sun, by utilizing good roof overhangs. It also helps to keep bamboo out of contact with the soil, so having it raised up on concrete blocks would be best practice.
Another way to minimize the effects of weathering on bamboo would be through the application of a sealer. Bamboo Imports sells a specialized sealer for bamboo, but a bottle of Thompson’s Water Seal can work just as well. If you are applying sealer to your bamboo, make sure to apply it AFTER the bamboo has been treated and cured.
When To Harvest Bamboo
It is very important to harvest bamboo at the right time to ensure longevity. Without proper harvesting practices, any future treating or drying of bamboo will not be as effective.
Bamboo is best harvested in the fall or winter in Hawai’i. This is a time when the sap is not moving within the stem. Cutting bamboo at this time will minimize any chance of splitting or cracking.
In addition, you want to be sure to harvest bamboo poles that are between 3-5 years of age. This is when the bamboo has fully hardened. A fully hardened bamboo pole is less prone to splitting, shrinkage and is harder for insects to bore into.
We covered how to gauge the age of .bamboo in an earlier article here.
Before cutting down a pole, inspect it for insect damage and any possible signs of disease. You will want to discard those.
When harvesting bamboo, any cutting tool will work. I like to use a chainsaw or a sawzall with a fine tooth blade. If you are into getting yourself a specialized tool, then try this bamboo saw, it’s one of my favorites.
Be sure that when you do cut down a pole that you cut just above a node as close as you can. This will minimize any chance of crushing the pole while cutting, which would cause splits in the pole.
5 ways to treat Bamboo in Hawai’i
Bamboo has to be treated in order for it to have longevity as a building material. This is to ensure the poles are not susceptible to damage by insects or fungus. Lucky for us, there are a few ways to do it.
This is a simple method of curing bamboo if you have access to water large enough to hold a full length bamboo pole. Either freshwater or salt water can work.
Soon after harvest, you’ll want to totally immerse your harvested poles in the water for 30-60 days. This will help leach out the starches and make the poles inedible to insects. The water also saturates the plant, allowing it to dry more evenly and slowly, which will decrease cracking.
Once done soaking, the bamboo poles only need 2 weeks to dry out if placed in a well ventilated area with sun exposure, but protection from the rain.
This is one of the simplest method for preserving bamboo. All you need is a 5 gallon bucket and a Borax based product called Solubor. Solubor is a super dissolvable borax that we mix 10% Solubor to water to create our treatment solution.
Cut bamboo and within 2-4 hours place it in the 5 gallon bucket with Solubor solution, base ends down. Make sure that you top off the solution every now and then as it gets soaked up by the bamboo.
This soaking action is enhanced by leaving the leaves on the bamboo and only removing the poles from the bucket after all of the leaves have died. About 1 week for smaller poles, 2 weeks for large ones.
I like to cut the bamboo and leave it standing in the clump, then just bring my 5 gallon bucket with the borax solution to the clump. That way the bamboo has the support it needs to stand vertically while it undergoes treatment in the bucket.
The boucherie method is a technique used for perserving bamboo that utilizes pressure to “inject” a 10% borax solution such as Timbor into the capillaries of the bamboo pole. Essentially what you are doing is replacing the sweet sap naturally occurring in the bamboo with a chemical that kills insects.
Care should be taken to inspect the pole for damage as this may inhibit the flow of the solution through the pole.
It takes anywhere from one hour to 24 hrs, depending on age of culm, to fully treat. You know when to stop once you notice solution coming out the other end of the stalk. Once you see this, wait one hour to ensure full absorption and then it is finished.
This system is great for treating multiple poles in a shorter amount of time. It can be made at home with the combination of PVC pipe, some rubber couplings and a small air compressor. It can also be done utilizing gravity as in this example from BONZA BAMBOO.
Related: Creating a Boucherie Pressure Treating system requires a small air compressor. Check out this one we recommend from Amazon. Low power for those off grid, but enough compression to get the job done.
VERTICAL SOAK DIFFUSER
This is not a method many of us would use. It requires a tall tower in which bamboo is placed vertically, base end up, in the tower. All the nodes are ruptured by rebar except for the bottom 2 and then a solution with 10% Timbor to water is poured into the bamboo from the top.
The solution is allowed to absorb for 14 days, after which the bamboo should be fully treated. This method has shown excellent absorption rates.
This method is easy for anyone to utilize. Simply make an outdoor fire or by using a barbeque, get the fire hot enough to the point that it creates a bed of red hot coals. Once hot enough, just run the bamboo pole over the fire, drawing out the resin and wiping it off as it surfaces.
The bamboo will begin to change color to a lighter green or yellow. The bamboo is then set aside to dry for 2 more weeks. I have had great success with this method. I have not yet experienced much bug damage utilizing this method but you do have to take care that you do not leave the stalk in the fire too long.
Drying Bamboo After Treatment
Once treated, it is important for the bamboo to undergo a drying process. Allowing bamboo to dry will keep it from cracking and will eliminate any shrinkage that naturally occurs in greener wood.
The most popular way to dry bamboo for commercial purposes. Once cut and treated, bamboo can be stored horizontally or vertically under cover and allowed to air dry.
Storing bamboo vertically allows for faster drying times and less prone to fungal attack. However it requires strong supports to keep the poles upright and free from warping.
For large amounts of bamboo, storing horizontally is the best method. Bamboo is laid on racks under cover from the sun. Ensure it is not stacked to high as the bamboo on the bottom tends to crack from the weight of the bamboo on the top. You can also lay the bamboo on a sheet of plastic if you can’t store them on racks.
Be sure to rotate everything every 2 weeks. It’ll take about 6-12 weeks to fully dry, depending on local weather conditions.
OTHER METHODS FOR DRYING AND STORING
Post Harvesting Transpiration
This method is utilized by peasant farmers across the world and is a great way to not only dry, but naturally treat bamboo. Simply cut a bamboo pole and prop it up on a rock so it doesn’t rest on the ground, leaving it standing upright resting on the other bamboo poles in the clump.
Leave the branches and stems on the pole and after 3-4 weeks through natural transpiration, the stem loses its humidity and naturally dries and preserves itself.
Best Practices For Long Lasting Bamboo Lumber
The above methods will help ensure that bamboo lumber will last a long time, but unless best practices are used, all the work you did to preserve and dry your bamboo was for nothing. Follow these simple tips to ensure long lasting bamboo.
A GOOD HAT AND GOOD BOOTS
There is an old saying in the natural building world that every structure utilizing natural materials must have a good hat and good boots. That means the roof better provide ample coverage and the base must ensure zero contact with the earth.
Bamboo gets destroyed with prolonged contact with the soil and doesn’t last long in direct sunlight or rain. Sometimes all it takes is propping bamboo up on a rock to keep it away from the soil, other times a more solid foundation may be utilized.
If you always ensure that your bamboo is well protected, it will be sure to provide you with many years of life.
DO NOT USE NAILS
Because of the nature of bamboo, whose fibers all run in the same longitudinal direction, using nails will instantly crack bamboo.
Instead predrill holes and use screws, or better yet, bamboo pegs to secure bamboo poles to one another.
HANDLE WITH CARE
Dropping bamboo or hitting it with a hammer may cause splits. It is important to handle poles with care. No use spending months curing the lumber only to be negligent when it comes to handling the bamboo during construction.
USE WEATHER SEALER FOR LONGEVITY
To avoid weathering, which naturally occurs even when taking above precautions, it is best practice to apply 2 coats of a sealer to the surface of the poles.
A high quality sealer is resistant to water and the harmful rays of the sun. It must be applied to the wall of the bamboo as well as to the ends. This will help seal up any possible points of entry for water or fungal disease.
A great sealer to use for bamboo is Bamboo Protector. This may be hard to come by however so I most often end up using Thompson Water Seal. It’s better than nothing.
There is no reason bamboo should continue to carry the stigma that it is not a long lasting material suitable for building with. Bamboo is a quality source of lumber that should begin to compete with imported wood products.
By creating local knowledge on how to properly use bamboo, we can move the conversation in Hawai’i towards how we can begin to utilize this most precious resource.
Bamboo has the potential to become a huge driver in Hawai’i’s local economy. A new workforce can be created through bamboo plantations, bamboo lumber yards and bamboo craftsmen with the experience to build homes and furnishings.
Most other countries in the tropics utilize bamboo as a major source of lumber for their construction projects, it is time Hawai’i did the same.
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