Let's Plant Bamboo-Guadua to Harvest Houses

There is definitely great potential in guadua for the solution of many problems, especially housing, and this without overlooking (especially with bamboo): food, production of ethanol - alcohol - cellulose - paper manufacturing - charcoal, medicinal uses , protective forests and many more.

Can you imagine that by planting 80 guadua seedlings today in an area of ​​1.300 M2 - approximately 31.50 meters x 31.50 meters - you can, after 4 or 5 years, "obtain in one go" a developed guadua tree, with the corresponding approximate material? to 130 stems or culms required to build the walls and structure of upper beams and columns necessary for a 60 M2 house, plus guadual as a perennial crop is still productive?

The above is perfectly possible not only in Colombia but also in most of the world, taking into account that in a native guadual tree, of the coffee zone type, technically exploited we can obtain 1.300 guadua culms or stems per hectare/year; or if it is a new crop we can begin to exploit it intensively from the fifth (5) year of sowing; which means obtaining the basic material to build 10 houses/year that, according to the policies, priorities and needs in the housing solution, we can adjust the cultivation and exploitation area; this without taking into account existing crops.

There is definitely great potential in guadua for the solution of many problems, especially housing, and without overlooking it (especially with the bamboo): food, production of ethanol - alcohol - cellulose - paper manufacturing - coal, medicinal uses, protective forests, carbon "sink", erosion control, landscaping and many more, we find in this, a resource that is little exploited and known in our environment in a technical and massive way. We have unfortunately known guadua in temporary and poorly made constructions (temporary construction camps, "slum" homes), which has led to a certain discredit; But in the same way as the rich or poor man's house is built with brick, the same thing happens with this one and finally it is not the material itself that makes the difference but rather an entire integral conception that makes it. Its importance is evident from the "I World Bamboo/Guadua Congress" -Pereira 1992- to the various forums and seminars on the subject and the recent "Symposium on the uses and services of Bamboo/Guadua" -Armenia 2001-. This writing is a contribution to the dissemination of a resource, of which there is very little scientific technical literature, guadua is a material suitable for many types of construction, especially social housing and about which, paradoxically, the Germans and Dutch know more, where they do not there is, that we ourselves where it grows wild. In the spirit of brevity, I omit in these notes aspects related to forestry, taxonomy, anatomical among others - developed in my book -; Additionally, as a result of my own experiences and research and at the request of my readers of a past article on the internet: "From the House of Guadua to the House of Paper Tubes" who asked me for more information about it.

HOUSING DEFICIT IN COLOMBIA AND THE WORLD

According to calculations of "HABITAT", the housing needs of the world population will double by the middle of this century; there are particular cases such as Africa, where it will triple. It is estimated that more than 600 million urban dwellers and more than 1000 million peasants in Asia, Africa and Latin America live in shelter that is "so crowded and of such poor quality with such inadequate provision of water and sanitation that their health and lives are continually at risk"; the supply of shelter is virtually destitute. The United Nations -UN- estimate that at least 100 million people in the world are homeless; the number reaches 1000 billion if "those with especially insecure and temporary accommodation, such as squatters, are included" (Brown 1999); this is where The beautiful, resistant and economical guadua becomes a true global alternative to satisfy the hunger for housing; additionally fulfilling a purpose of replacing the use of wood with another alternative, economical construction material suitable for a region of high seismic activity.

In Colombia, although it is difficult to determine the housing deficit due to the strong internal and external migration flows; According to a CAMACOL report of June 2001, based on the 1993 census, the current housing deficit in the country is concluded to be more than 1.400.000 units. "At the end of the year 2.000, 6.180.000 were estimated in Colombia. 1990 urban households and on average in the decade 1999-182.000 an average of 128.000 new households were created each year, of which 4 with incomes less than 1.040.424 smlm. (at $495 which corresponds to XNUMX USD$)

FIRST THINGS FIRST: SOW GUADUA

Of the once immense native guaduales destroyed to expand the agricultural frontier, in Colombia, it is estimated that only 54.000 hectares remain today; Therefore, promoting its cultivation is the first priority and although it is a perennial crop, its importance lies in finding substitute materials for wood due to its high cost and the great deforestation suffered by the environment. Constructions with guadua have proven to be a safe system - see the report of the earthquake in Armenia, Colombia, in January 2000 - especially, taking into account the high degree of seismicity that our country and Latin America in general face. My specific proposal consists of developing a construction policy with guadua that begins by strengthening laboratories like that of: Cordoba -Quindío, Colombia- for the cultivation of seedlings or "chusquines" -the most efficient form of propagation- whose sizing also To address a reforestation policy (protective forest), it also encourages its industrial exploitation, which is our objective. 

To plant one (1) hectare, approximately 625 seedlings/Ha are required. -if it were carried out in a 4 X 4 meter planting grid. which depends on many factors - as a reference, the planting cost per hectare is estimated at $39.900 pesos/HA (USD $197) and for its management at $388.500 pesos/HA (USD $185) for a period of 5 years including the value of labor. Assuming that said propagation laboratory operates continuously for a certain period, we will obtain the necessary material to reach the planting goal and with such an area obtain the necessary material to sustainably build - starting from the fifth year - a certain number of homes per year, the above without taking into account the existing guaduales and their exploitation possibilities. Assuming that the average present value per mature stem in said plantation is of the order of $1.500 pesos (0,71 USD $) which corresponds to the current value in the guadual; We will have that for the projected house of 60 M2 with 130 stems or culms, the cost of said basic input would be of the order of $195.000 Colombian pesos of December 2000 (92 USD $) to the above we must add transportation and immunization and the rest necessary materials that are different from this, such as: the reinforced concrete foundation - similar to that of a conventional brick house - electrical, hydraulic and sanitary installations with their corresponding devices, panels, paint and cover.

VEGETABLE STEEL

One of the current problems regarding the physical-mechanical characteristics of guadua is that the documentation of said research is not approved; to have an order of magnitude and given the seriousness and representativeness of the tests carried out by the "German Civil Construction Materials Testing Institute of Stuttgart" in November 1999 for the ZERI pavilion of Colombia at ExpoHannover, in guadua variety "macana" coming from the coffee zone; We present their results, warning that these do not correspond to the limits but to the design limits: 1) Compression. Sigma: 18 N/mm2, Lamda: 0, Modulus of Elasticity: 18.400N/mm2 2) Tension. Sigma: 4 18 N/mm2, Modulus of Elasticity: 19.000 N/mm2 3) Flexion: Sigma 18 N/mm2, Modulus of Elasticity: 17.900 N/mm2 4) Shear: Tau -without cement in the tube- 1.1 N/mm2 5) Specific Weight: 790 Kg/M3. Conclusion - and by way of comparison - an iron rod with a section of 1 cm2 - less than ½" - resists 40 KN in traction. (Kilo Newtons); a guadua with a section of 12 cm2 resists 216 KN. That is why it is called : "vegetable steel"!.
Let us remember that guadua works very well with flexo-compression and traction, in the latter the problem is how to hold it efficiently; It works very poorly when bending and flattening perpendicular to its length; Therefore, the guadua structures must be calculated as articulated bars in the ties; since in none of these nodes can it be considered as a porticoed structure or an embedment.

SECOND: BUILD WITH GUADUA

In Costa Rica in 1988 there was no guadua - there were other varieties of bamboo - and just 3-4 years after planting, 2.000 homes were built with this material; The "National Bamboo Project" (PNB) decided to build 7.200 bamboo houses at low cost. In Bangladesh there are 15 million houses made of bamboo. By planting guadua, a variety of bamboo, we can harvest ecological houses with excellent earthquake-resistant characteristics due to its light and very flexible "vegetable steel" characteristic, a renewable natural resource that, unlike wood that is cut and must be replanted; The guadua is not cut but pruned; Taxonomically, bamboos belong to the most primitive, diverse and least studied family of Poaceae (grasses), the so-called subfamily Bambusoideae; from which the variety of "Bambusa Angustifolia Kunth" or guadua is derived; a true dinosaur from the plant kingdom; It is not a forest species (tree), it is a grass, that is, a giant grass from the same family as corn, rice and wheat; It is the fastest growing plant species; It can grow on average 10 cm per day; unlike timber trees that require about thirty (30) years to be harvested and used in construction. The pine, which is one of the fastest growing forest species (tree), takes 15 years to be used; Guadua can be used after 4 years of planting when it is already mature and suitable for use in construction.

It must be taken into account that the good design of a construction and its earthquake-resistant properties are the product of the correct application of a series of design and construction principles, namely: 1. Regular shape. 2. Low weight. 3. Greater rigidity. 4. Good stability. 5. Firm soil and good foundation 6. Adequate structure 7. Competent materials. 8. Quality in construction 9. Capacity to dissipate energy and 9. Correct fixation of finishes and installations.

The horizontal forces that generate an earthquake are directly proportional to the mass or weight of the construction and its height or "center of gravity"; Consequently, the greater the weight and height, in the event of an earthquake there is more acceleration and greater damage. Due to their low weight, guadua constructions have excellent performance against these. Let's look at some figures:

The weight of a cemented bahareque wall is between 90 and 130 Kg./M2; A hollow cement block wall weighs 250 kg/M2 and if it were made of adobe it would be between 500 and 700 kg/M2. A wooden mezzanine weighs 70 to 90 Kg./M2 compared to one made of reinforced concrete joists and plates that weighs 400 Kg./M2, a galvanized tile (Zinc) roof weighs 20 Kg./M2 including the trusses; The one made of asbestos cement tiles weighs 30 Kg./M2 and if it were made of clay tiles it would weigh 90 Kg./M2.

Every year, earthquakes and earthquakes confirm the lack of respect for good construction standards; The properties of "strong" materials do not necessarily guarantee strong buildings, because bricks are inflexible and have a serious problem due to their high specific weight. The modern earthquake-resistant buildings in Kobe, Japan, when the 1995 earthquake occurred were too rigid to withstand the shock waves and failed. Bamboo or guadua canes, on the other hand, are very flexible. The earthquake of January 2000 in the coffee region knocked down almost all the brick buildings, in addition to various reinforced concrete structures and even some bahareque houses with rotten foundations; although in general they responded quite well; Many studies were done to establish the physical-mechanical properties of Guadua and they confirmed that the tensile strength is comparable to "vegetable steel"; The importance of protection by design, protection against all types of humidity, adequate anchors and avoiding too rigid triangulation was highlighted. The establishment of special construction standards with Guadua is also required and a law to be added to the current Earthquake Resistant Standard is close to presidential sanction in Colombia. 

PLATES AND SCREWS

The current development of the system is based on the use of 3/8" screws with their respective nuts and washers and the use of 7/8" x 1/8" plates and clamps, all of them screwed and since the guadua works poorly to crushing in the supports or crossings between them, this is compensated by filling the tubes with cement and sand mortar 1:3 or 1:4.

As we see, the correct design and construction concept is essential, it is a matter of specialist knowledge. If your construction is made of guadua or cemented guadua bahareque, do not add brick walls or similar heavy elements that make it vulnerable to an earthquake. Remember that guadua construction is characterized by being light and flexible, faithful to the Chinese principle that says that "bamboo that does not bend breaks. Although it may seem incredible in the city of Armenia - the "Mecca" of guadua in Colombia - it is find the ruins of a deplorable and recent experience of poor management and design in a small urbanization carried out by the same municipality where the most basic principles of design and construction were overlooked, resulting in the total deterioration and abandonment of said homes by of its inhabitants in less than three (3) years of having been built; but there we also find, as in all of old Caldas, Tolima, Cauca River Valley and Antioquia, excellent examples of houses built a hundred years ago that are found intact and that of more recent constructions very well designed, built and preserved in this material. 

Building with guadua cemented bahareque is at least 20% more economical compared to traditional brick, iron and cement construction and its durability lasts for many generations if the rules of its proper use have been followed.

EMPLOYMENT GENERATION AND COMMUNITY ORGANIZATION

Constructions made of this material do not require specialized tools and allow intensive use of unskilled labor, although there must be a professional and a master craftsman in charge; This contributes positively to job creation. We do not propose here the revalued self-construction system because it is uneconomical; We propose design and construction with community participation so that each individual actively contributes to the quality and definition of their own home and leads them to appreciate and reevaluate the concept that the above has about this type of material within the concept of Companies Community Construction. The experience of Costa Rica teaches us that the project has allowed the planning of a community organization system, through housing committees in each of the communities, forming groups of beneficiaries who have received technical advice from the PNB. In many of the communities the system contributed to their development, not only in terms of the construction of houses, but also in the repair of roads, drinking water, improvements in their health conditions and marketing of agricultural products.

HISTORICAL AND CULTURAL ASPECTS OF BAHAREQUE.

In Colombia and Latin America, bahareque architecture is the product of the fusion of elements contributed by indigenous people and colonizers that gave rise to a mestizo architecture: bahareque, adobe and to a lesser extent the rammed earth, which in turn They constitute the most frequent ways of working with clay in our construction tradition. The rammed earth and adobe were the European contribution of the colonizers and given the high seismicity in the coffee region they were quickly abandoned due to their vulnerability to earthquakes. All of them have a common ingredient: mud.

The bahareque is native and corresponds to the constructions that our indigenous people made and is their best legacy; The bahareque houses were built using the original covering of the interwoven structure of reeds, sticks and/or guaduas, it was a mixture of mud, straw and dung; a framework with forks or guaduas nailed directly to the ground and tied by vines; As walls, a wall was built with vertical or horizontal elements made up of "cans" of guadua or thin wood, forming a kind of box which was filled and then a plaster or mud cloth was applied. The roof was made up of a main framework made of thicker wood as beams and a secondary one with thinner rods or reeds and covered in straw, which later evolved into zinc tiles and baked clay tiles. 

DECALOGUE OF GOOD MANAGEMENT OF GUADUA FOR CONSTRUCTION

Here is a brief summary of aspects more widely developed in my book:

1. Select and previously mark the guaduas that you are going to cut. Use "jechas" or mature guaduas of 4 or 5 years. Although this occurs from sea level to 2.600 meters above sea level, those located above 1.300 meters above sea level -coffee zone- have the best physical and mechanical characteristics.

2. Cut in the "waning" lunar phase between the hours of midnight and dawn. 

3. Perform "bleeding" or "vinegaring" on the bush; leaving them stored there vertically and protected from the ground for 20 to 30 days.

4. Clean and wash them with water and then let them dry naturally or artificially, squeezing them very well so that they dry evenly and then leave them indoors until they turn yellow.

The previous steps correspond to the basic treatment that our ancestors practiced and that today allows us to have bahareque houses with more than 100 years of construction and in very good condition against pest attacks. 

5. Immunize it, preferably use natural products that are not harmful to humans. "Pentaborate" is a good, proven, safe, economical option that does not cause harm to man or the environment. Smoke treatment, widely used in Japan, although little technically experienced in our environment, is an excellent option. "Vacuum" immunization is very good although the most expensive and it goes without saying that there is a wide range of chemical products from different laboratories for its preservation, some that are worth more than guadua itself and others that threaten human health. In "organic" agriculture there is a wide range of natural immunizers to be investigated.

6. The guadua must be protected from the elements (sun and water) and properly protected from capillary humidity, therefore it must be placed under a roof and protected with large eaves and good pedestals and/or sockets above the floor, with a height minimum of 40 cm to protect against splashes of rain and capillary water, following the principle of having "good boots and a good hat."

7. Do not use nails, nailing the slit; Make holes using a drill and use washers and nuts. Properly make the ties between guaduas in "fish mouth" and those appropriate for tying cylinders. After 6 months of construction, retighten the nuts.

8. As a final finish and protection against the sun's ultraviolet rays that discolor and damage it, and as an insect repellent, an application based on linseed oil with turpentine, or bitumen. Do not use enamels, these do not allow you to breathe.

9. Carry out comprehensive maintenance on the construction, preventing pests, humidity and deformations. Keep in mind the 5 enemies of guadua which you must resolve and anticipate in your design and construction:

1. Water, humidity and weather, which cause rot.
2. The fire, which consumes it.
3. Fungi and insects, which attack its structure and destroy it.
4. The ultraviolet rays of sunlight that discolor it and make it more vulnerable to the previous agents.
5. Bad design and poor construction that destroy it quickly.

Dear reader, I hope to leave you some good concerns about this material that serve to promote its study, research and use. Many successes already in "Planting bamboo/Guadua to Harvest Houses" consistent with its knowledge, correct management, good design and excellent construction.

* By By Mario Francisco Alvarez Urueña. Architect graduated from the "National University of Colombia". Bogota 1977.