Low cost vault made with bamboo

Low cost vault made with bamboo


“The main advantages of using bamboo for roof constructions are:

• It is a traditional technology, which is well understood by local artisans. No special tools are required.

• The large-scale utilization of bamboo has no disastrous environmental consequences (as in the case of timber), on account of its quick replacement within 4 or 5 years.

• The physical properties of bamboo make it an ideal construction material for seismic areas.

• Compared with most other building materials, bamboo is cheap to buy, process and maintain.

• This construction system was developed at the Research Laboratory for Experimental Construction, Kassel College of Technology, Federal Republic of Germany, headed by Prof. Gernot Minke.

• It demonstrates an unusual use of bamboo, in which the construction obtains its stability by compressive forces, acting perpendicularly to the bamboo’s axis.

• On the principle of masonry barrel vaults, full-section bamboo culms are laid horizontally, one on top of the other following a curve, defined by an inverted catenary. (This is a curve formed by hanging a uniform chain freely between two points. The tensile forces induced by gravitation run along the line connecting the points of contact of each chain link. Since the curve remains stable when reversing the direction of forces, an inverted catenary is the ideal shape of a barrel vault.)

• Split bamboo strips of equal length are hung such that their ends are exactly the same distance apart as the ultimate roof span. The full-section bamboo culms are laid horizontally forming an inverted vault. Split bamboo strips are then laid on the inside, exactly opposite the outer ones. Holes are drilled through the split and whole bamboo and fixed by bolts or rivets.

• The whole structure is then turned over and fixed on the top of the walls, which preferably should have a timber or concrete ring beam, onto which the roof is connected.

• The roof should be covered with a waterproof membrane for rain protection. This can be covered by a suitable local thatching material, or more appropriately by a 10 cm layer of soil on which grass can grow. For initial reinforcement (to prevent slipping) the soil should be held down by a strong net (as used for fishing). The dense structure of the grass roofs will give the soil cover its ultimate stability.”

Source: Humanity Development Library 2.0 – Appropriate Building Materials


Comments

Bamboo Barrel Vault — 8 Comments

  1. Hey Owen, I recently bought a sizeable piece of land in Taiwan and I am going to build three small natural structures. The land is full of bamboo and clay. I’ve done loads of research and now I have a question about a hypothetical design. Do you think the dome could be reinforced with rammed earth? So, in-between each pole is lets say a two or there foot span. What if you rammed earth into this span while framing it with split bamboo pieces to hold the earth into place. Maybe ad lime and fiber (saw grass is at my site or bamboo shoots) to help solidify it. The final structure would then be covered in two layers of 6mm plastic sheeting and a grow bed of recycled fishing nets would span the top upon which grass could grow. I’m considering using water glass (potassium hydroxide) and lime water as the method of preserving the bamboo and ensuring it is dried two years before usage to avoid shrinkage. And of course, a stone footing and good rubble trench. What do you think? I can start building on my land in two years, so I want to work out several design by then for the three small structures and get all my materials ready. Thanks for your time!

    • You need to keep researching and experimenting to see what will work because what you describe has probably never been done before. Can bamboo be bent into the desired radius after you’ve treated it? Will it support a living roof? Living roofs are very heavy. Bamboo in contact with rammed earth could easily rot.

      In general bamboo is best used above ground with a lightweight thatch roof.

    • Thanks for the response! I was also thinking rammed earth might lead toward rot however I saw houses being built like this in India, so it got me to thinking. I thought maybe using something similar to a hemp-lime-san mixture that is lighter and highly breathable. The lime ought to help with rot problems as well if applied correctly. I was also thinking of curing the bamboo the the desired shape as it dries. The bamboo I have available is of a variety of sizes ranging from about as round as a CD disk to thinner pieces about as round as a plum. I figured using bigger bamboo for beams and spacing the beams close together may be enough to hold a living roof. Time to experiment with something small I guess! Thank you for the advice!

  2. No need to buy any bamboo.
    Plant a few shoots and soon you will have more bamboo than you can possibly use.
    The neighbors can use some of it to build a nice multi platform gallows to hang you from and give out bamboo sticks to the kids to beat your swinging hanging corpse like a pinata for your planting recklessness.

  3. I’d love to be able to use bamboo for different projects but, I have NO clue where you can buy it besides some place that sells it just for decoration for the home. Any ideas where you can get it here in the U.S.

  4. Given bamboo’s strength in tension, it seems an odd choice for a catenary arch. Or are we thinking of this as the lightweight reusable form discussed under ‘Ferrocement Vault with Cardboard Backing’?

    • This looks like a freebie method for temporary shelter, don’t you think? This would not be the best choice for ferrocement because of the large profile. It would use too many materials. A low arch like yesterday’s blog post would be much more efficient for ferrocement.

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