Construction Of Paper Log Houses For Disaster Victims In Bangladesh Using Bamboo Material

Project Strategies for successful multidisciplinary and construction:

• To provide a more secure housing development in the midst of nature changes.
• Building durable long-lasting structures that will be strong under their living conditions
• To advance natural and individual cleanliness of the general population to ensure their wellbeing which incorporates better water supply and sanitation.
• Utilizing inexhaustible materials however much as could be expected
• To provide a more grounded structure to the houses which can withstand tremors, substantial breezes, tempests and ailments.
• Integrating sustainable strategies, for example, water harvesting, vegetation, and natural products.
• It is expected to outline the structure which gives poise, security of individuals and protection. Likewise, to give adaptability in outline which encourages the clients to include segments in the houses for better protection.
• Low building heights permits manual development which lessens energy use amid development
• To give utilization of sustainable power source by creating sunlight based boards on the rooftops and furthermore rain water collecting framework is introduced to reuse the water for cleaning reason and furthermore for little rural practices.
• Design expects to decrease

Materials Selection

Natural disasters are very common in Bangladesh and when they occur, they displace many people. One of the immediate needs of these people are houses but most of the victims usually do not have the finances t rent or built new homes immediately. The aim of this report is to examine the construction process of paper log houses meant for disaster victims in Cox’s Bazar, in Bangladesh. These houses are primarily made of bamboo, which is a locally available, low-cost, flexible, durable, environmentally friendly and sustainable building material. Their design is also efficient, functional and safe for use by disaster victims. The report comprises of three main sections: materials selection, fabrication process, and design & section detailing. Materials selection section discusses various properties of bamboo that make it suitable for this project. Fabrication process discusses different techniques and processes involved in preparation of bamboo and construction of foundation, floor, walls, and roof of the paper log houses. Design & section detailing comprises of different joints/connections, plans, sections and elevations of the houses.

Materials Selection

There are over 1,000 species of bamboo worldwide ad 21 species in Bangladesh. These species have unique properties and therefore suitable for different applications. Some of the species used in this project include Bambusa Nutans (for the system in the development) and Bambusa Balcooa (for auxiliary components such as posts and beams). Bamboo has proved to be a reliable building material in Bangladesh and has been used for this purpose for many years (Ma'ruf, 2017). Besides being used in building normal houses, this material is also mostly used for building houses for disaster victims. This is because the material is easily available, cheap, easy to use and durable, among other properties (Escamilla & Habert, 2014); (Wang, et al., 2014). Some of the key specifications and properties of bamboo are as follows:

Dimensions

Bamboo is available in different sizes. The bamboo used in this project had a height raging between 8 and 16 meters and diameter of up to 175mm. The bamboo used for foundation, posts/columns and beams had an average diameter of 150mm while that used for walls and roofing had an average diameter of 80mm.

Bamboo is hollow and generally stronger than most typical building materials such as steel, concrete, wood, bricks, etc. Its tensile strength, which goes up to 400N/mm2, is greater than that of steel because of the highly elastic axial fibers. Its compressive strength, which goes up to 85N/mm2, is close to that of steel. Its bending strength is also greater than that of steel.

Bamboo Properties

Elastic modulus

The outer parts of bamboo has fibers that give it a high elastic modulus. This property makes bamboo a suitable building materials in earthquake-prone areas because it can withstand substantial bending before failure.  

Buckling

The nodes present on bamboo protects it against buckling because they allow substantial bending before rupturing.

Anisotropic properties

Bamboo has unique properties in the longitudinal and traverse directions. Cellulose fibers, which are rigid and strong, are present in the longitudinal direction while lignin, which is soft and brittle, is present in the traverse direction (Kumar, et al., 2017).

Lightweight

Bamboo has a low weight, making it easy to transport and use. It has a very high strength-to-weight ratio (Disen & Clouston, 2013). This material does not require use of heavy machinery such as cranes as it can be easily carried and placed by people.

Fire resistance

Bamboo has high content of silicate acid, which gives it very good fire resistance capability. When filled with water, bamboo can withstand very high temperature of up to 400°C (Raj & Agarwal, 2014).

Shrinking

When it loses water, bamboo can shrink more than wood. It shrinks both in cross section and wall thickness, and can break at the nodes (Chen, et al., 2009). Therefore it is important to dry the bamboo before using it as a structural component.

Earthquake resistance

Because of the enormous elasticity, bamboo is highly resistance to earthquakes.  

Availability

Bamboo is easily available in Bangladesh. This minimizes procurement and transportation costs.

Flexibility

Bamboo is highly flexible making it easier to cut and bend it into any desired shape.

Cost

The cost of bamboo is relatively low compared with other building materials. The availability of this material locally further reduces its cost. This is one of the reasons why bamboo is commonly used for building emergency houses (YR Architecture+ Design, 2017).

Fabrication process

The fabrication process of the paper log houses in this project entails all processes from the time of harvesting bamboo to completing the roof of the houses. These processes are as follows:

Harvesting

The bamboo used in this project had to be 3-5 years. Before harvesting, the bamboo were inspected physically and only those without defects were chosen. The ones selected were strong, straight, long and mature. The harvesting was done by cutting the bamboo using a handsaw, chop saw and machete followed by removing the branches.

Drying

As stated before, bamboo shrinks substantially when it loses water. This shrinkage has implications on properties of bamboo as a structural component. To avoid this problem, bamboo had to be dried. The method used to dry the bamboo was air drying, which is the most common method (Schroder, 2012). This process involves storing bamboo poles vertically in a shade for six weeks, as shown. The shade was adequately ventilated and the bamboo poles were protected from soil moisture, rain and direct sunlight so that their properties could not deteriorate.

Fabrication Process

After drying for six weeks, the bamboo poles were inspected to remove the ones that had developed defects in the process of drying. The team did not take any chances and therefore inspected all the bamboo poles for defects.

Straightening

There are different methods of straightening bamboo but as a measure to cut down cost, the bamboo poles in this project were straightened by use of fire, as shown in Figure 2 below. When passed over fire, the bamboo becomes more elastic after reaching a certain temperature, which makes it easier to bend and straighten (Haugen, 2016).

Bamboo is vulnerable to attacks by fungi, moulds, insects, pests, bugs, termites, etc. These attacks deteriorate structural properties of bamboo hence have to be prevented. The bamboo in this project was treated using borax and boric corrosive solutions. A pool of this solution was prepared then bamboo poles were dipped into it and left there for seven days to allow the salts enter into the bamboo. After the seven days, the bamboo poles were removed from the pool and placed vertically in a shade to allow the solution dry off, as shown in Figure 3 below. After drying off, the bamboo poles were moved into a storage area.

Classifying and sizing

After treatment, the bamboo poles had to be classified based on use. They were put into four groups: columns/posts, beams, wall and roof. The classification was done considering the size (length and diameter) and straightness of the bamboo poles. Thereafter, the bamboo poles were cut into the desired sizes using a machete and handsaw. Besides cutting, some of the m were split into halves (to be used for walls and roof).

The construction method used in this project was ground up. This simply means that the construction started from the ground (foundation) and moved upwards – from the foundation to floor, walls the roof. After all the preparation of bamboo poles, actual construction process started with the foundation. Bamboo poles are not required to be exposed to moisture and the team had to come up with an innovative idea on how to prevent this. They decided on using beer and soda crates to make the foundation of the paper log houses. The crates were donated by individuals, companies and businesses within the area. They ensured that bamboo poles did not touch the soil to prevent a decline of their durability. The crates also helped in providing a horizontal levelled floor. The beer or soda crates filled with sand are resistant to rain, snow, flood and other weathering factors. This increases the stability and longevity of the houses. To start with, 1m deep holes were excavated at the four corners of the house and paper tubes installed in them. These paper tubes had two functions: to support the building, and also to restrain the building from any movement. The paper tubes used in this project were made from 100% recycled paper. These tubes are very durable and they have similar characteristics as corrugated cardboard. The durability and sustainability of the paper tubes were increased by coating them with a rainproof substance. Bags of sand were filled into the crates then the crates were placed in one square foot holes on the ground, one after the other, until covering the entire floor area. One of the uses of the crates was to weight down the house’s foundation. This helps in lowering the center of gravity of the house thus increasing its stability. 13 x 13 foot plywood floor was placed on top of the crates. Plywood was a good choice for the project because it is durable and easy to clean and maintain (it only requires sweeping). After installing the plywood flooring system, pegs were placed at its outer perimeter. Paper tubes were then placed over the pegs. After placing the paper tubes, waterproof and weathering proof sponge tape was used to seal the joints between paper tubes. The tape is used as an insulation material. 2.25 inch steel rods were then horizontally slipped through pre-made holes in the paper tubes slightly above the plywood floor to hold the tubes strongly together and provide horizontal support. The structure s as shown in Figure 4 below

Foundation

The walls of the paper log houses in this project were made of crushed bamboo mats. These mats were made from split flatted bamboo poles. To make the mats, bamboo poles were split and opened into individual strips, as shown in Figure 5 below. The nodes were broken using a hatchet then a spade was used to cut the bamboo pole vertically (Guadua Bamboo, 2018). The cut bamboo was then pulverized adequately to ensure that it is properly straightened. After breaking all the nodes, the bamboo poles were easily opened and a mallet used to crush them into flat mats.

After flattening the bamboo mats, it was necessary to remove and clean the inward whitish layer found inside bamboo. This was so as to prevent the mats from being attacked by insects and bugs. The mats were also preserved against molds and insect attacks by curing. This was done by submerging the bamboo mats into a pool of water and non-toxic preservatives for a few days and allowing them to dry thereafter (as shown in Figure 6 below). The individual bamboo mats were then joined to each other at the edge of their length using very small nails, with a small overlapping allowance to create straight paper tubes. Crushed bamboo mats are very strong, durable and environmentally friendly (Guadua Bamboo, (n.d.)). It is important to note that crushed bamboo mats were made from green bamboo and later allowed to dry before being fixed.

Bamboo poles were fixed at a distance of 1.5m from each other all round the house, with the paper tubes standing at each corner of the house. Horizontal bamboo poles were fixed at the centre and near the top of the vertical paper tubes. This created a proper framework for installing the mats. The crushed bamboo mats were then attached to the framework of lashed paper tubes and bamboo poles using small nails, as shown in Figure 7 below. The walls used in this project were different from the ones used in the original paper log houses built in 1995 in Kobe, Japan. In the first paper log project, the walls were made of full bamboo poles joined together on horizontal beam-like members.

To have a quality and good looking finish, crushed bamboo paste was plastered on the internal and external sides of the bamboo wall, as shown in Figure 8 below. Besides attaining a good look, crushed bamboo paste also adds strength to the walls, makes them more plastic and acts as an infill to prevent entry of wind, insects and rain into the house. The crushed bamboo paste also improves privacy inside the house.  

Floor

The roof in this project was covered with tenting materials i.e. fabric or plastic membranes. The roof was inclined at an angle to facilitate flow of rainwater. If rainwater remain stagnant on a roof, it lowers its structural soundness hence the roof cannot last longer. Therefore the roof water waterproof hence it protected the inside of the house from weathering elements such as rain, flood and snow, and also preserved the house’s internal elements. The roof frame was made of bamboo poles. The poles (rafters and purlins) were cut into desired sizes then attached on the bamboo beams fixed at the top of the bamboo columns/posts. The bamboo beams were fixed by sliding them through pre-made holes in the bamboo posts. Some roof joints were done by tying the members together using G.I. wire, ropes and bamboo threads. The tenting materials used to cover the roof are also low-cost. The main challenge with the tent-like roof used in this project is that it is vulnerable to being blown or carried away by strong winds. For this reason, stakeholders should look for a way of replacing the tenting material with other suitable materials that will improve safety of the house and the targeted victims. After covering the roof with tenting material, nypa palms were placed over the material, forming a thatched roof. This enhanced the rigidity of the roof making it withstand strong winds. The nypa palms used are shown in Figure 9 below (Chin, 2014).

Construction equipment

There are no specialized or heavy equipment and machinery needed in this project. The houses are constructed using very simple and basic tools. They include handsaw, machete, nails, hoes, hatchet, spade, mallet, etc. These tools do not consume any fuel or water. For this reason, the tools used did not produce carbon emissions that would have impacted the environment negatively.

The construction technique used in this project is very simple. It takes about 20 people to construct one house in less than six hours. Since there is no specialized expertise needed, the disaster victims themselves provide the labour and work under supervision of a technical person. The construction process can only be successful through full support of the locals. The local residents can provide the required materials, such as bamboo poles, and labour for free.Safety was given a top priority during the construction process. The team ensured that all possible causes of safety risks and hazards were prevented or mitigated. Even though the workers were not in appropriate personnel protection equipment, the supervisors ensured that basic and fundamental safety precautions were taken into account. The main challenge was that the work was done urgently and the team could not organize for all the desired personnel protective equipment.   

Walls

The general construction process of paper log houses is similar regardless of where they are being constructed but with small variants depending on locality constraints. For instance, instead of using beer or soda crates to make the foundation, it can be made using rubble from nearby demolished buildings (if any). The floor and wall can be made of mud or any other appropriate materials available locally and cheaply. The roof can be made of split bamboo poles, grass, iron sheets or any other suitable material. In other words, the choice of material can vary depending on what is locally and easily available. Nevertheless, the materials used should also be selected carefully so that they do not slow down construction process. Since the houses are built during emergency, these materials have to be easy to transport, cut, bent and install.

It is important to note that all materials used in this project were prefabricated. These materials were only taken to the construction site for assembly. Prefabrication has become very important in construction industry as it speeds up project delivery (Jaillon & Poon, 2010), minimizes material wastage (Vivian, et al., 2007), lowers construction cost and improves safety of workers (Fard, et al., 2017); (Jaillon & Poon, 2008). In fact, construction experts say that prefabrication is the future of construction (Dy Buncio, 2018) and it is rapidly transforming the industry by improving quality, reducing cost, increasing safety, increasing speed and minimizing waste (Mesaros & Mandicak, 2015).

The construction process used in this project is very sustainable. The process is sustainable in terms of the materials used and the techniques of construction. The sustainability is not only during construction but also throughout the houses’ lifecycle because they can last for many years with minimal maintenance. The main reason why the construction process is sustainable is because it has very minimal impact on the environment. In terms of materials, the foundation of the houses is made of beer crates and bags of sand. The crates were donated and the sand was obtained locally. It therefore means that the foundation materials did not produce any direct carbon footprint. The walls and part of roof were made of bamboo poles and paper tubes. The bamboo poles are renewable materials while the paper tubes are made from 100% recycled paper. The roof is made of tent materials. All these materials are easy to make and low cost hence they have very low levels of carbon footprint. Most importantly is that the materials are locally available thus there is no transportation costs and their associated carbon emissions. In terms of actual construction, there is no energy used at al. All processes are done manually without using any electricity or fuel. This is very different from typical construction processes where large equipment and machinery that consume fuels are used. Additionally, very little water was used – only when mixing crushed bamboo paste.

Roof

Otherwise all the construction activities were done using materials and simple tools that did not require water or energy. So the entire construction process had near zero carbon footprint. This makes it a very sustainable construction process. Beyond construction process, all the materials used to make the paper log houses are durable. Their natural nature enables them to withstand a wide range of environmental or weathering elements.

Therefore paper log houses have positive social, economic and environmental impacts. They are socially sustainable because they provide shelter to disaster victims when they need them most. They are economically sustainable because they are low cost – constructed using low cost materials and tools. They are environmentally sustainable because they are constructed using natural and locally available materials and simple tools, which have low or zero carbon footprint.

Connections of bamboo structures are relatively complex mainly because of the nodes present in bamboo poles. Nevertheless, the houses can only be strong and stable if the bamboo poles are joined appropriately. Figure 10 below shows a 3D representation of the paper log house. This figure shows that there are different types of connections in this house at the foundation, wall and roof. Some of the members are connected horizontally, vertically and at an angle. The stability of the houses largely depends on these connections hence it is very important to ensure that all members are properly secured to each other

3D representation of the house

The bamboo poles used as columns/posts in this project were specially shaped at the top to accommodate horizontal bamboo beams, as shown in Figure 11 below. The connection is referred to as splicing by use dowels.  

Some bamboo beams were also cut at the top so as to accommodate vertical members fixed onto them as shown in Figure 12 below.

Beam-column connection

Other members of the paper log house were joined using ropes, G.I. wire, bamboo threads and other kinds of binding, as shown in  His kind of joints is usually used when the members are not supporting very heavy loads. The binding has to be tightly tied so as to secure the member properly.

The connection shown in Figure 14 below is known as positive fitting. In this connection, a hole of desired size is made through one bamboo pole then another bamboo pole with the same size as the hole is slashed through it. After that, biding is used to tie the members together at the joint.

As stated before, modular or prefabrication construction is the method used to build the paper log houses. As shown in Figure 15, the house was divided into different elements called modules. There was the foundation module, flooring module, wall module and roof module. Each of these modules was prefabricated offsite and taken to the site for assembling. But even though the modules were prefabricated offsite, and probably in different places, the prefabrication process was done through proper coordination and integration of the team to ensure that they fitted into each other perfectly. Any slight error could result to losses and delays thus integration and cohesiveness of the team was crucial.

Paper log house modules

below shows the plan of the house. This plan basically shows the top of the house’s foundation i.e. the layout of the beer/soda crates and the plywood flooring.

The roof structure of the paper log house. This structure shows different points where the roof members were connected. Some details of roof connection are shown in Figure 20 below.

Below shows the plan and section of the foundation of the paper log house. The figures show how vertical and horizontal bamboo poles were connected to ensure stability of the houses.

The role that integration and cohesiveness played in successful completion of assignments 1 and 2 cannot be overemphasized. If anything, we largely dedicate the success of the two assignments on these two elements. As a team, we worked professionally to ensure that each member of the group accomplished his successfully ad on time. We successfully evaluated the proposed refugee village and the site (Cox’s Bazar in Bangladesh) where the 50 houses were to be constructed for the 50 people who were victims of disaster. Based on the basic needs of these homeless families, we selected paper log house as the most suitable design for the locality. This design was the best choice because of the available building materials in the area, urgency of the need for these houses and our past experiences on similar projects. We then evaluated each element of the paper log house and created the following drawings: plan, foundation, elevations, sections and cross sections of different elements of the house. We considered a wide range of factors when designing the houses, such as cost, functionality, size, ease of construction, safety, durability and sustainability. We then identified the most suitable construction process for the project i.e. prefabrication and modularity. After analyzing the construction method, we came up with the budget for the project. From the budget estimates, the total cost of one paper log house is 2,721.6 AUD, which is very low in comparison with typical houses in the area. In general, assignments 1 and 2 were very successful because we managed to come up with the most suitable design, identified the best construction method for the project and estimated the cost of the project. Therefore at the end of these assignments, everything was ready to implement the project by building the 50 paper log houses for the disaster victims.

Conclusion

These assignments gave us an opportunity to put our vast knowledge and past experience into practice. Abhishek, a design consultant, was the design planner in this project. Lohith, a project manager, was in charge of developing the construction methodology in this project. Adithya, a prefabrication specialist, was in charge of modularity. Last but not least, Praveen, a cost planner, was in charge of cost estimation. Despite the fact that we all completed our assigned tasks successfully, there are several ways in which we could have improved our experience.

First and foremost, we would have improved our experience through training. There are numerous trends, changes and developments going on worldwide in different sectors. Construction industry is among those that are transforming rapidly because of technology. For this reason, there is always something for people to learn from training. Through training, we would have met new people, interacted with them, acquired knew knowledge and learn something new (Savelsbergh & Storm, 2010). This would have enhanced our experience in this project. Through training, I believe that we would have completed the project more efficiently, quickly and at a lower cost. Some methods of training include attending seminars, workshops, conferences, consulting online, etc.

Another way of improving our experience is taking time to learn other’s strengths and weaknesses. Even though we did not have time to do this, due to the urgency of this project, we would have improve dour experience had we known each other better. By doing so, it would be easier for us to communicate with each other and also predict what we should expect from one another. People who understand each other are likely to work seamlessly that strangers working together (Zehra, 2016).

We could also have improved our experience by organizing for a creativity and innovation competition among ourselves. We could simply challenge each other to come up with the most innovative or creative idea for the project and award the winner a small token. This would definitely make each one of us thinking out of the box so as to win the prize. At the end, we would learn new things, develop experience and also make the project more efficient.

Integration and cohesiveness had several positive impacts on the final outcomes of the project. First and foremost, it helped us come up with the most functional and efficient design for the paper log houses. Second, it enabled us complete the project quickly and at the lowest cost possible. Third, it facilitated communication among us. Fourth, it helped us understand each other better thus preventing conflicts and disputes that could otherwise have cause delays. Fifth, it helped us criticize each other positively, which played a key role in providing the best solution within stipulated time and budget. Last but not least, integration and cohesiveness enabled us make the right decisions quickly and take appropriate actions for successful completion of the project.

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