Green Home Building: Bamboo House Construction

Q: I'm interested in finding an introductory book, or several books on the basics of building a simple wooden cabin/hut/house in the tropics. I am interested in Bamboo as there is a lot of bamboo here in Jamaica.

A: There should be a book on this subject--maybe I should write it. I do have a manual on building the hooch--a single point foundation treehouse that is appropriate for the tropics. I like the design, but there are certainly other designs out there--mostly more conventional. You can see various versions of the hooch on my website, www.tropical-treehouse.com

There are several overriding design principles of building with bamboo in the tropics. First, a large overhang keeps the structure dry and out of the direct sun--this protects the bamboo from rot, bleaching, and ultimately a shorter life. Keep the bamboo exposed to air, and easily accessible- this prevents the possibility of critters taking up residence, and easy replacement if needed. Besides, bamboo is nice to look at--structural beauty.

The structure should be raised off the ground, with no bamboo in actual contact with the earth. This, again, prevents critters access, including marauding termites (who need access to moisture, ie, earth). The bamboo stays dry if not in contact with the earth. The hooch has a single point foundation--only one place where bugs can enter--so it is easy to monitor.

Also, although some species of bamboo are naturally resistant to bugs and rot, the bamboo should be treated with an earth-friendly preservative. The best treatment is borax, but this is water soluble--another reason the bamboo should not be exposed to rain (large overhang).

The roof may need to be some other impermeable membrane, as it is a bit difficult to keep this dry. I use plywood coated with elastomeric roof coating- cheap, and simple. You could do a metal roof, just keep things light (another good general rule).

If I were to pick one book on bamboo, I would choose "Bamboo: The Gift of the Gods" by Oscar Hidalgo. I met the guy a couple years ago, as we were judging a bamboo dwelling contest. Quite the character. He covers the whole spectrum, including houses, traditional and proposed. Thick! Also, the results of the competition I alluded to was put into a book. Lots of ideas, though not all practical. There are the pre-fab dwellings that are produced by Bamboo Technologies, out of Hawaii, that are tried and true. www.bambootechnologies.com/ www.bamboocompetition.com

Q: Can bamboo be treated to stay in water as some types of wood are treated to stay in water?

A: I suppose bamboo will take up any treatment used for wood to withstand water--I can think of a couple epoxy types used for boats. The skin of bamboo is fairly impermeable, so a treatment should be able to access the meat of the bamboo from the inside (knock out the nodes).

Q: You do not mention lashing as a method for joining bamboo. Do you recommend against this for use in hooch construction?

A: Lashing is a traditional method of joining bamboo, and is still appropriate. I use galvanized wire as lashing--though not in any traditional way. Wire lashing is used on ends to prevent splits from developing, and maintain the structural integrity of the bamboo pole. I also have used a lashing technique for securing mortise and tenon joinery--with a wood block insert. The goal of good joinery is to prevent any relative movement of the joint, and design the joinery such that the structure is totally triangulated. The hooch does this nicely. Also, joining more than two pieces at a joint is somewhat problematic, and less strong. A staggered joinery is a good alternative. I have not used traditional bamboo lashing--even in furniture designs. The bamboo scaffolding in Asia uses black polypropylene rope.

Q: I have built an 11' x 14' sunroom addition, in a corner of my house here in RI. It is a 3 season place, lots of sun when the maples have lost their leaves. It has a cathedral hip roof, coming down onto very stiff beams at the top of the perimeter walls (part of which are tied to original house). Still, I feel the need for a tie rod across the width (11' span), across the middle. I had thought of a pipe, or rod, disguised inside an 1 1/2" culm of local yellow goove. Then I thought it would be cool to run a couple more 11' culms 24" from each end, then run 14' poles on top of these, also about 2' away from side walls. This is to provide a kind of lattice structure, for hanging planters. So now the original center pole is both a tie rod, and holding up stuff(besides itself). So it starts to look like some kind of truss, maybe an arched floor truss? And I wonder if the center culm could be somehow fastened to each side wall, in tension, without a threaded rod piercing thru all the nodes? I don't mind making the holes thru the nodes, but have heard that will weaken the structure, maybe making it unfit for it's other function (supporting some planter weight, away from the middle of the span. I also think I could use some of the natural crooks that aureosulcata forms, as struts between an upper bent arch & the lower main tie culm. The design & joining techniques are what I would appreciate advice about. I just want everything to look visually light, or I'd just run a big old oak beam across there!

A: Whoa, nice project. I too am in the final stages of a sunroom addition here in Ashland, Oregon. Mudding and taping the drywall on a 10 by 15 space, with a gable cathedral ceiling. The ridge is tied into the roof of the rest of the house, with a center support at the outside peak, and well tied in, so tension rods are not an issue with this project. But, a way cool idea--I might follow up on your idea--just to have the lattice structure for hanging plants.

So, thanks for the clear description of the project, and dilemma. Classic. I've had similar design problems. Probably the best example is the overhanging roof at the treehouse in Puerto Rico. I have a tall, large diameter bamboo that looks to support the corner. But, actually, the roof corner is cantilevered out--so little support is actually needed. But, inside the bamboo, I ran a 1/2" rebar, tied to a solid, underground foundation, and then tied into the roof. The object here is not to hold the roof up, but to hold the roof down from uplift during a hurricane.

But lets deal with your concept. Knocking out the nodes for the threaded rod does not diminish the strength of the bamboo in tension. It will, however, under extreme bending, buckle sooner, as the nodes prevent the walls from collapsing--like a bent pipe. I think that you will not experience that extreme of bending distortion.

However, with those spans, the lattice structure will sag with the weight of hanging plants. I would support the center bamboo with a tension bamboo to the center of your hip roof. This should be enough to prevent the sagging. Threaded rod inside bamboo would work great. I have also used galvanized wire--a loop from an eye hook in the ceiling to a wrap around the lower horizontal bamboo. With a nail through drill holes in the center of the vertical bamboo, and through the two wires inside the bamboo, the bamboo can be turned, causing the wire to twist, and tighten up the end joint snug. It works also.

As for using bamboo without the internal rod--yes, bamboo has a high tensile strength, but the difficulty is in the joinery--as you surmise. Unless you go through heroic measures with the joints (epoxy?), you cannot devise a joint that is stronger in tension than the actual bamboo--so the joint will fail first. Tension bamboo bridges interweave bamboo with long overlaps--that does works also.

Another issue. Using whole bamboo culms, even properly cured, may have some problems in cracking/splitting. When exposed to humidity fluctuations, and the heat of direct sun, bamboo shrinks and expands differently, inside and out, creating huge stress, causing splits. This not only does not look good, but, obviously, it blows the structural stiffness.

I do not know the diameter of your proposed bamboo, (1" - 2" ?). If the poles (11' span) do have an internal threaded rod or other tension reinforcement, and it is supported from the ceiling at the center, I think that you may get away with some loss of structural integrity of the bamboo. I say this in order to justify the pre-splitting of your bamboo--the splits on the upper side (so you cannot see them). This strategy is only for aesthetics. It will prevent further cracking--as the stress from humidity and temperature are relieved. The crack will be open, and further prevent a disparity in humidity and temperature between the inside of the bamboo, and the ambient conditions. This will weaken the bamboo. Whether it is too much, or whether you will need to increase the number of bamboo lattice pieces, depends on the strength and diameter of your bamboo.

Now. plant hangers: Check these out ( on Google 3D warehouse): http://sketchup.google.com/3dwarehouse/search?q=bamboo+plant+hangers&styp=m Just some designs for bamboo plant hangers. Some use split, large diameter bamboo, others use several small diameter bamboos. Simple to make, and I think they would fit your decor.

Just some thoughts. I always like to have multiple functions for a particular architectural element, but sometimes you may need to back it up. Department of Redundancy Department.

Q: I am about to build my dream home in Rodrigues Island (Mauritius). It's taken me 43 years to reach my goal and I want to do it right. Are there some golden rules and advice you could give me. Rodrigues is in a cyclonic region...and we have severe water shortage and building materials are very expensive. I can access a lot of bamboo on the Island. How could I use bamboo in my construction?

A: Do your research. There are lots of books out there on bamboo construction. Bamboo- the Gift of the Gods , by Oscar Hidalgo is one of the best. Otherwise, no big overhangs, build with open walls, windows, to reduce windage. Anchor bamboo with cement footers, but do not sink the bamboo into the cement- use rebar sticking up out of the footings, then attach the rebar to the bamboo (with cement/through bolts). Do not allow the bamboo to come into contact with the wet earth- it will rot. Protect the bamboo from exposure to direct sun/rain/prolonged moisture- it will deteriorate.

It is best to treat all bamboo components with Borax, infusing the culms with a pressure treatment, the Boucherie method, works best- but is a bit of an effort. Taking fresh cut bamboo and allow them to sit in a bucket of borax solution, still upright, works well (the natural uptake of water through capillary action with get the borax in the tissues.

Always triangulate structural components. The style is up to you. Check out traditional buildings in your area.

Q: Can you give me instuctions on how to make a bamboo hut?

A: Build it anyway you want, but use something else for the roof, and keep the bamboo away from rain, moisture, sun, and not touching the ground. Be creative-bamboo bends!

Q: I am a senior in college studying architecture. I am designing a bamboo home in one of my upper division classes and am wondering if there is any specific length/span used. What I am trying to get at is what size grid should I use when designing (ex. for wood you would use increments of 4' and for steel 10' to generalize it)?

A: The current ongoing effort to establish building standards, ie, strength, deflection, spans, etc., has a very difficult task before it. Though tests can be devised and some ballpark strengths can be elucidated, bamboo is not standard. Its strength varies with species, diameter, node spacing, wall thickness, which section of the culm the piece is from (upper culm vs lower culm), and age. The one place where bamboo has been approved for building, and standards have been established, is Hawaii- and that is only for one species of bamboo.

Also, the deflection standards for the building industry, is very strict. Bamboo, though very strong and resilient, even with large deflections, would have to be used way beyond what is necessary to keep deflections within limits (people do not want to feel movement in their dwellings, and the standards reflect that. If a dwelling were less than 120 square feet, you could build a bamboo structure more in line with the material- flexible, resilient, and strong.

When building an all bamboo hooch in Costa Rica last year, we tested the floor joist spacing (5-6" bamboo) with the flooring being bamboo "esterilla"- multiple split bamboo that is folded out as a board. Though thin, it was very strong- and flexible. I think our spacing ended up to be 16" o.c.- similar to normal wood flooring layout. So, a specific grid layout would be similar to wood. Always triangulate, keeping joinery components at two (trying to join three pieces of bamboo is difficult, weaker)

Long lengths of bamboo, with tapering diameter, can be incorporated as vertical members also, up to about 24'.

Q: I am a true novice to bamboo, but was hoping to use some in renovating the top of a barn for my living space. I found 70 pieces of fresh cut - 2"-3" diameter, 30 feet long. Can you explain to me, in the simplest methods possible, as to how I can get this ready to use the poles to cover a pitch ceiling (attic type) bedroom and if I can get the poles usable, how do I attach them? I also have other ideas in mind for their use - if I can just get them usable?! I think I my have gotten these and now won't be able to use them, which would make me very sad. I live on a small farm in the north Georgia mountains, little money, and building as green as possible, by myself mainly for me and my grandson. After all I have read, I'm starting to feel maybe I won't be able to do this. Can you help me in any way?

A: Quite the project. I am not really clear on the building situation, but I will attempt to offer one strategy. The barn roof is good at keeping the rain and snow out, and you just want to build an inner wall/ceiling to possibly insulate the space and/or otherwise make the space more livable. Yes?

And you do not have a lot of tools, or are adept at their use. Here is what you do: Take the best pole- thickest/strongest, and install it as the ridge pole- just under the ridge of the barn- say 1 foot down. Support it at both ends with wood supports or even bamboo that extends down to the floor. Also, depending on the length, support the ridge pole with galvanized wire wrapped around the bamboo pole and hung to the existing barn ridge. This piece is very important, as it will support all subsequent bamboo poles along the ceiling wall.

Cut poles to length, (just more than the length from floor to pole along the ceiling), lay poles, alternately, from floor to pole. Use all the poles, or as many as you can, in this arrangement. You can then lay a vapor barrier over the whole bamboo arrangement (6 mil polyethylene). Sealed at the base and ends, the barrier will reduce infiltration- at least from the ceiling. You can stuff insulation between the bamboo/vapor barrier and the barn roof as you install the vapor barrier- working your way across from one end to the other.

The bamboo remains exposed- which is nice. Basically, it is a tent within your space. Covering the poly with, well, anything, in a patchwork (depending on what you have, or can find) will make a very cool (make that warm) space. This is only an off-the-cuff suggestion, but something I would do under this situation.

Q: What do you think of using 2-3" diameter- (10" long) of properly harvested and treated (boric acid) bamboo as the rounds in a cordwood building? The site is in Hawaii, very wet at 1200' elevation, but of course bamboo cordwood wall is overhung from above. This bamboo is old, has filled in center hole, or almost has. The ones which haven't I'll either fill with our big batch of lime putty, or caulk. We are using a lime putty mix- no concrete. Wall is not load bearing, as it is part of post and beam building. Cordwood part sits on 30" lava rock foundation/wall.

A: I see no reason it will not work. The bamboo is thick walled, apparently, very strong. A large overhang is very important, as well as good ventilation and no contact with soil - which you addressed. Cool! Post some pics.

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