Basic Principles and Techniques
How to join bamboo, or what are the best bamboo joints? Well first of, it is important to know a few basics principles about joining bamboo before discussing the different techniques. So here goes...
- Do not use green, fresh cut bamboo. Bamboo has to be completely dry before using it in construction (preferable air dried). During the drying process the bamboo diameter shrinks, so when bamboo is used in joinery this will result in lose and weak joints after a few weeks.
- Do not use bamboo when it is less then 3 years of age. Only use mature bamboo of 4-6 years.
- Do not use bamboo infected by insects (powder beetle for example). Bamboo has to be properly cured with a boron mix immediately after harvesting.
- Do not use bamboo that has flourished. Rest assured bamboo only flourishes once in a lifetime (60-120 years).
- Do not use bamboo poles with profound vertical cracks.
- Use appropriate cuts and joints when building with bamboo.
- Use bamboo with the right diameter and wall thickness for your project.
- Do not use conventional wood nails in bamboo joinery, they will cause the bamboo to split. Instead use nylon, steel or vegetal cord of the appropriate diameter.
- When using bamboo as a column make sure that the lower part connecting with the surface ends with a node. If not the bamboo will splinter when struck (for example to position the column).
- When connecting bamboo poles with bolts, make sure to bolt them together in between 2 nodes, otherwise the bamboo may crush. More about utilizing the nodes below...
Bamboo Has Nodes, Use Them!
In construction, using bamboo nodes is very important. Bamboo columns or beams need to have a node at both ends (or as close as possible towards the ends), if not the pressure of a structure on the joint may crush the bamboo.
Often it isn't possible to find bamboo of the required length with both end nodes in place. When this occurs you should insert a wooden cylinder of the appropriate diameter or a fitting piece of bamboo with a node.
These are the most common cuts to use when making bamboo joints:
one ear / two ear / beveled / flute mouth / fish mouth
As you can see in the illustration below, making basic cuts in bamboo doesn't require expensive or heavy power tools, just a few traditional hand tools will work fine.
Bamboo Joinery Techniques
Making good and aesthetically pleasing bamboo joints is rather complicated because bamboo is hollow, tapered, has nodes at varying distances, and it is not perfectly circular. It is important to keep all these constraints in mind when designing a bamboo joint.
Although traditions, local practices and publications give some information on bamboo joinery, this information is far from complete as essential data is missing in most cases. Many traditional joinery techniques suffer from weakness or deformation, where the strength of the bamboo culm itself is lost.
Before bamboo gets widely adopted in modern architecture (and becomes affordable for all to use), the problem with bamboo joints and universal joining systems has to be solved. After all, timber, steel, and more recently prefabricated concrete, only became proper building materials for the same reasons. How many cumbersome solutions for joints have one seen, before these materials became a standard in construction?
Only if the problem with bamboo joinery can be satisfactorily addressed, and simplified, we can expect to see much more bamboo in Western buildings, bridges and furniture.
Below you'll find some examples and illustrations of traditional bamboo joinery techniques.
Joining horizontal with vertical elements
1. Joint with one or two ears. Is used to join bamboo rafters, logs or lumber.
4. Flap joint. Is used when there is no lashing wire available. The flap can be secured with bamboo strips.
5. Fish mouth joint.
Use of dowels and anchors in bamboo joinery
1. Joining bamboo with dowels and lashing. The peg should be placed in the column parallel to the rafter.
2. Fish mouth joint with pegs.
3. Bamboo joint with wooden anchor. Is also used inverted.
4. Bamboo joint with metal anchor. This technique Is used in various positions.
Double and quadruple bamboo rafter support
1. Beams formed by 4 or 6 members. The top row is separated from the bottom with bamboo or wood slats so that the upper bamboos do not slide over the lower.
2. Central double rafter. It has a wide range of applications in the construction of bridges and structures for rural facilities.
3. Lateral double rafter. Each of the rafters is secured independently at the side support and each other. It is often used in the construction of bridges and structures for rural facilities.
4. Lateral double rafters. Is often used as a central support for bridge structures or sheds.
Joining and fixation of bamboo poles
1. Joint with double wooden wedge.
2. Joint with dowels and clamping fitters.
3. Cross joint with dowel.
4. Lateral joint with dowel.
5. Corner joint.
Splicing bamboo poles
1. Top splicing.
2. Bevel splicing.
3. Ray splicing
4. Half bamboo splicing.
5. Splicing with internal union.
6. Splicing with external union.
7. Telescope splicing.
Source: Oscar Hidalgo Lopez, Manual de construcción con bambu.
Ask a Question or Share Your Comments:
Stephane from Guadua Bamboo wrote:
Making a Bamboo Fish Mouth Joint
This video from the Technology Institute in Costa Rica shows a basic technique in bamboo construction: the bamboo fish mouth joint. Notice the backslash of the drill in the beginning of the video. Guadua bamboo is a thick walled timber specie, so be careful when you try this at home!
Typical reliance on the modern speed tools rather than traditional tools, techniques and skills. This work requires a coping saw and appropriate rasps, not a bunch of hodge-podge reaming with hole saws on electric drills.
I had a Japanese scoutmaster in the boyscouts. Making bamboo joints goes notably faster with hand tools.
A man who knows how to really use a machete can do far better, faster, simpler and certainly safer.
Notch the bamboo when green. There is very little waste and the kickback danger shown using power tools is avoided. There is nothing green about the use of power tools.
Hardwood round T's inserted into the dried and treated bamboo allows for expansion from dry to wet season.
As a designer architect I visualize in my work with bamboo it is essentially a post and beam construction.
Bamboo posts in wet locations are treated as if they were hardwood. Pilings are formula cement pours with welded (not wire tied) rebar cages with the bamboo column set into using rebar up through the column and also shooting a slurry of cement (different formula) into the base. This the same concept done to stabilize columns in earthquake/hurricane/tsunami construction. The piling with its rebar armature must be at least one meter into the ground/base with at least five inches of packed small gravel at the bottom of each piling. The ground/foundation area must be packed and left to settle at least one rainy season. The better the pilings the stronger for settling and earthquakes. A distance on center of pilings is = no more than 2.5 meters. Three smaller diameter (3-inch) bamboo columns together equal are the equivalent of 10-inch column if set correctly.
I like the idea of using a wine bottle and will experiment with same.
The Japanese perfected the used of bamboo in small footprint structures, fencing and wall/floor matting. Yet, I would not suggest using these tie and bind methods in a two story shelter in Latin America.
I also would never use a bamboo exterior roofing system in Latin America. The lifespan of a bamboo roof (covering) compared to a double coated metal roof one is about maintenance and safety.
I work in the Pacific southern zone of Costa Rica. Besides the intensity of the rainy season the sea air is a serious factor.
I have found that forming a fish-mouth in three steps is fast and accurate. First I cut a 'V' shape to the correct width and depth with a handsaw. Then I use a curved chisel to remove the remaining bits and complete the shape. I check the fit and if there are some high spots I use a round rasp to remove them. This is fast, accurate and requires no electricity - something we rarely have here in Nepal.
"Improving" on traditional techniques is what brought us to high embodied-energy construction. It appears to be human behavior to constantly modify/improve without consideration of consequences or necessity.
I think that building with round bamboo is only suitable for the very poor, or the very rich... It takes too long to do it right, not to mention the waste from constantly trying to make the bamboo joints acceptable to 'high-end aesthetics', or it looks like crap... I use a stationary motor with a tapered grinding stone, when I have to do it, but the dust is noxious, and it still takes too long...
My solution has been to make the rough joint bearing points as close as possible, and to use wood plugs as you do, but to make the bamboo joint pleasing to the eye, I just use spray foam (I know, that's not too eco appropriate) which stabilizes and fills the gaps, then trim it with a sharp razor, and paint it to match. It comes out looking like your pictures, and stops bugs from attacking the end cuts, and takes a fraction of the time to do...
I also use wine bottles foamed into the ends of bamboo poles for bearing on the ground, or connecting two bamboo poles into one longer one. Sometimes I put a few LEDs in the ends on the ground to make a cool way to keep from stubbing your toes in the dark...
Stephane from Guadua Bamboo replied:
You hit the nail on the head. Much has to be done to improve the way round bamboo poles are joint together.
Filling Bamboo Joints with Cement
I saw some info about creating strong bamboo joints when using Guadua in building construction, especially adding cement to the joints. I recall threaded rod and hardware being used, and possibly rebar as well. I would love to see more detailed info and/or videos about that. Perhaps there are some good videos on the site already that I have missed.
Carl Tuck wrote:
Joining Bamboo for a Stair Railing
I am using 2" bamboo poles for a railing for a stair and i want the pieces to be continuous. I have 8 ft lengths but want the railing to be about 20 ft long with rail brackets every 3 to 4 ft.
I was thinking of putting either wooden dowels bridged across, and inside the connecting poles glued with loctite premium adhesive or maybe a pvc pipe of the appropriate inside diameter might serve to bridge the gap, glued with the same adhesive.
Do you think one of these ideas would work or do you have a better idea?
How to Join Split Bamboo?
Hello Guadua Bamboo team, I will be building a low cost pig farm in a nearby village with the help of unskilled villagers to avoid high construction cost. I will be using bamboos for the roof, vertical support pillars and horizontal support beams. My idea is to split bamboo and use half bamboo for the roof to create a broad skeleton and then put tarpaulin on top of it.
My question is...
How to join half split bamboo to other half split bamboo horizontally for a roof?
How to join half split bamboos to full round bamboo (round bamboo can be horizontal support beam or vertical support beam)?
Proyecto pyramide wrote:
How to Join a Bamboo Pyramid?
I am using guadua as the corner posts for a pyramid. Any suggestions as to how to join these at the top would be greatly appreciated. The lengths of the posts will be 8.5m, the pyramid base 9m x 9m. The height at the apex 6.5m. We need to get the joint exactly right to ensure the energetics of the structure are correct. Suggestions as to how to raise the posts are also appreciated.