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Curing bamboo for building in tropics  RSS feed

 
Posts: 1
Location: Hilo, United States
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Aloha all!

I want to build with this amazing three mature patches of bamboo that we have growing in the back of the homestead. Not sure the specific species but grows 40 feet easily and the inside is between 3/4 - 1 1/2 " thick. We want to use the thickest ones to build a very simple structure. In the past, not curing the boo, they last only 18 months. Which is not bad for free material. Does anyone have knowledge on how to cure bamboo in the wet tropics to resist termites for a longer life?

Thanks in advance!
 
pollinator
Posts: 1736
Location: Toronto, Ontario
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I wonder how a Shou Sugi Ban method would work. Or something like kiln-drying cut lengths of bamboo.

If you got yourself a length of black PVC piping, the larger the gauge the better, you could cap it on one end with a one-way valve for release of expanding gases and moisture, fill it full of lengths of bamboo, cap the other end, and sit it out in the sun. I don't know how many hot days it would take, but I am pretty sure this would cook a lot of the volatile organic compounds and dessicate it, leaving no nourishment or moisture for bacteria or anything else.

You could build a similar retort out of a material that would work in a fire, and heat it that way. You would have to experiment at low temperatures, finding out exactly how hot you could get it before you damaged the structure of the bamboo, but you could easily use a biochar-style production method with split sections of bamboo to produce an exterior cladding that wouldn't rot at all, and that could also be used in the same manner as those half-cylinder clay roofing tiles, to produce a water-tight roof that would also clean the rainwater as it ran off.

Fascinating topic. Thanks for posting. Let us know how it goes, and good luck!

-CK
 
pollinator
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I have read similar ideas as presented by the previous post, except involving several metal barrels welded together end to end with the ends removed, so as to make a long metal tube, into which whole bamboos are placed, and the whole thing sealed up, and stood on end in a slow fire, which simmers the bamboo in its own juices, so to speak, driving these up through the vascular channels, and then it condenses at the cooler top end and runs back down into the boiling liquid at the bottom. 
     Lacking this, the curing protocol I was taught years ago at a workshop involved several steps. 1. choosing 3 year old and older canes to cut.  With some species this can be determined at a glance as the waxy deposit just beneath each joint turns from white to dark as the cane ages past two years.  2. cut them and leave them stand held up by the surrounding bamboo till the leaves dry out, removing excess moisture.  3. pull down, trim branches and cut to desired length.  If the bamboo is to be split, it is easier to do now.  4.  Bundle and submerge the bundles in water for a month.  This leaches sugars and starches out of the canes, making them less susceptible to insect damage.  5. Pull them out and leave to dry slowly in the shade, especially with whole canes, and either flat or supported in a vertical position so they dry straight. Something like 75% should thus dry down without excessive cracking.
      Building with bamboo is an art in itself, and numerous resources exist.  One of the basic principles, and a big challenge to those of us used to working with wood, is to try not to use any penetrating fasteners (nails, bolts, screws, pins, etc.) which will inevitably split the bamboo, later as it cures and flexes if not immediately.  Use fasteners that wrap around the canes, like wire or twine, whenever possible.  With whole canes a compromise can sometimes be reached by putting a solid wooden plug into the open end of a cane and fastening through this, or even filling an end joint with concrete, with fastener in place....
 
Posts: 40
Location: Costa Rica 100 meters above sea level, Tropical dry forest
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Punch out all divisions except the bottom 2. Stand on end in a barrel.
Make a solution of boric acid and boiling water. Pour this into top end of bamboos. Let soak and refill for a couple days. This will help.
Can find more info on amount acid per gallon online.
 
Posts: 6
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I've treated thousands of bamboo culms, in most cases I use borax. The basics are similar to what has already been mentioned. One thing I suggest is to do more research from lots of different sources, rather than to start building with an unknown species. Here's some pointers:
- Identify the species, make sure it's suitable for building
- Cut mature culms (3+ years)
- Clean with scourers and detergents
- Drill through the whole length, to allow the borax to enter, so it can be absorbed
- Immerse in a 10% borax solution.

For building:
- Design in planes
- For joints, lash or drill holes and use dowels or threaded rod

I could add more info, but it's better you spend a couple of days reading, there's a lot of info on the net.
 
Posts: 25
Location: Limpopo, South Africa. Sub-tropical, summer rainfall, 1200m.
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Steve Marr wrote:I've treated thousands of bamboo culms, in most cases I use borax. The basics are similar to what has already been mentioned. One thing I suggest is to do more research from lots of different sources, rather than to start building with an unknown species. Here's some pointers:
- Identify the species, make sure it's suitable for building
- Cut mature culms (3+ years)
- Clean with scourers and detergents
- Drill through the whole length, to allow the borax to enter, so it can be absorbed
- Immerse in a 10% borax solution.

For building:
- Design in planes
- For joints, lash or drill holes and use dowels or threaded rod

I could add more info, but it's better you spend a couple of days reading, there's a lot of info on the net.



This is very interesting. I have just planted 20 young Bambusa balcooa out and hope to start harvesting in about 3 years. They are a clumping, non-invasive species which grows well here. I have noticed a few feral bamboo groves nearby - most likely Dendrocalamus asper - which no-one seems interested in so I may go and harvest to build a shadehouse.

When you say you immerse the cut bamboo in the borax solution, how do you practically do this with 10 metre + culms? Also how do you drill through such a long length? I assume once you manage to drill through then you could fill the cavity with the borax solution and stand it upright for a few days?
 
Posts: 61
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I’ve been researching bamboo construction and uses and will offer this entry I found on Wikipedia on leaching bamboo for construction (originally from here.

Leaching is the removal of sap after harvest. In many areas of the world, the sap levels in harvested bamboo are reduced either through leaching or postharvest photosynthesis. Examples of this practice include:

Cut bamboo is raised clear of the ground and leaned against the rest of the clump for one to two weeks until leaves turn yellow to allow full consumption of sugars by the plant.

A similar method is undertaken, but with the base of the culm standing in fresh water, either in a large drum or stream to leach out sap.

Cut culms are immersed in a running stream and weighted down for three to four weeks.

Water is pumped through the freshly cut culms, forcing out the sap (this method is often used in conjunction with the injection of some form of treatment).
In the process of water leaching, the bamboo is dried slowly and evenly in the shade to avoid cracking in the outer skin of the bamboo, thereby reducing opportunities for pest infestation.

Durability of bamboo in construction is directly related to how well it is handled from the moment of planting through harvesting, transportation, storage, design, construction, and maintenance. Bamboo harvested at the correct time of year and then exposed to ground contact or rain will break down just as quickly as incorrectly harvested material.

 
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