Building systems

32. Construction Design Considerations

Building systems:

Superadobe . Also known as earthbag construction, superadobe consists as using sandbags of earth, stacked, and tied together to form a structural basis for a building. Superadobe consists of a few main elements: • Sandbags; often polymer or burlap. • Filling; moist soil, sand, and possibly small amounts of stabiliser such as cement or lime. • Barbed wire Render; covering to the sandbag structure, can be plaster or clay and earth, but often a mix of both.

These materials are cheap, easy to transport, and most importantly common to the local region of Baghere. Earth and sand are natural components that could be harvested locally thus minimising the need for transportation of what is the largest and heaviest element of the construction. The tools necessary for superadobe construction are basic hand tools such as shovels and tampers, which are easily obtained locally. Superadobe requires no heavy machinery. (Cal-earth, 2020)

33. Construction Design Considerations

Superadobe is known for its ease of construction, requiring only basic construction techniques which would be easy to impart onto the local workforce. There is no operation of unique tools or machinery and the process is relatively safe. It mostly requires simple manual labour, such as digging the foundation trench, filling, and stacking the bags, with the wire placed to tensile strength. Much of the structural elements are easily moved by hand and can be filled in place with no heavy lifting which can allow for participation of more demographics of the population. (Cal-earth, 2020)

Figure 13: Process Diagrams for Superadobe Construction (Diagram by authors)

34. Construction Design Considerations

Superadobe, when coupled with passive design strategies, has excellent thermal properties. It allows for steady maintenance on internal temperatures even with hot or cold exteriors as superadobe has relatively low heat transmittance. There is also a high degree of thermal inertia, which allows heat stored in the walls during the day to be released at night. This coupled with a natural cross ventilation can allow the project to maintain a stable temperature in the comfort range. (Rincón, Carrobé, & Medrano, 2019) Superadobe is also a strong form of construction, with earthbags giving compressive strength and wire adding tensile strength. Superadobe is often constructed in a circular fashion with domes and arches which have strong load bearing and distribution properties that can help resist external forces. The sandbags also add flooding resistance and the structures curvature and flexibility give it the properties needed to withstand extreme weather events, and if damaged can be repaired with locally available materials. (Daigle, 2008)

Earthbag construction is widely regarded as one of the most sustainable and environmentally friendly forms of construction. With properties that allow for passive design strategies, low energy needs, and minimal usage of materials consisting of high embodied energy, it will have a far reduced negative environmental impact compared to other construction techniques such as concrete or baked bricks. Having locally available resources also means less impact through transportation and allows us to be certain that materials are ethically sourced. (Sinclair, 2006) Superadobe has been used before in Senegal and near Baghere in Tanaff. The process of construction allows for cooperation and collaboration with the locals, and after consultation, if appropriate can allow for involvement of demographics such as women, hopefully increasing agency, and empowerment There aesthetics and materiality of superadobe are not out of place in the Baghere region and typically allows for a inclusion of other types of construction methodologies, such as other roof types, that can be more traditionally culturally relevant and typical of local vernacular typologies. (Salo, Polyvalent Cultural Center, 2018).

The materials for superadobe are cheap and easy to source in the region, helping to cut down on transport costs. No expensive machinery or trade experts are required, and the building process is relatively quick, which can help keep labour costs low and reduce chances of delays due to extraneous site conditions. (Pelayo, 2020)

35. Construction Design Considerations

Treated Bamboo and Sheet MetalRoofing . Bamboo is a lightweight timber with strong tensile properties that will be used as framing for sheet metal in the roofing structure. Bamboo is common in southern Senegal and grows in large quantities there, where it is often used as a construction material and in many other goods such as paper and furniture. As a versatile plant, bamboo has seen an increase in commercialisation globally as well as in Africa, with organisations such as the International Network of Bamboo and Rattan (INBAR) leading the effort to promote sustainable use of the timber and increase access to information and technology, in the hopes that it will promote bamboo production and growth. Senegal is a member nation of INBAR (Musau, 2016). As the plant is in high frequency, access to the timber should pose no issue for the women's house. This also includes the borax salt required for treating the bamboo, should it need to be harvested or treated locally. It is also to be grown as part of the landscaping section of the women's house as part of the project's sustainability aspects, hopefully replacing the amount used and contributing more bamboo to potential future developments in the area.

Bamboo being strong, lightweight, and cheaply available makes it an ideal roofing solution, and has been used frequently as such in the region. Bamboo roofing systems can be constructed by hand, and easily taught to the local population. Bamboo is often used as scaffolding during the construction process and requires little in the way of extraneous resources to utilise effectively. Once treated it can last for 25-30 years and will be elevated to avoid any issues with pests and termites. (Humanitarian Benchmark Consulting, 2018) Sheet metal, despite having a high embodied energy, has a multitude of advantages. It is lightweight and easy to install onto a bamboo framing, meaning the community can easily be involved in the construction process. It is durable and will last for years, which is important with permanence being a concern for the local population, and when compared to other systems such as tensile roofing, sheet metal is less prone to warping and tearing. This is especially important as water security is a major component of the project. A sheet metal roof will be able to capture water and withstand the high-water volume of the monsoon season without pooling or tearing, thus having to be frequently replaced. A secure, clean water source is vital and the resilience and reliability that a sheet metal system offers is valuable.

36. Construction Design Considerations

We elected to use a structural system consisting of bamboo truss members consisting of three main bamboo members, which could be assembled on the ground and lightweight, so could be moved into position by hand. These are fixed to the superadobe structure via the use of rebar inserted into the structural bagging of the main walls.

The bamboo battens are then laid across the trusses and the sheet metal fixed in place. This creates a large yet sturdy area for rainwater collection that can withstand the monsoon season's extremities and utilises the available and inexpensive resources. The elevated open roofing solution also allows for cross ventilation, which is especially important in Senegal's humid and warm climate, accentuating the strong thermal properties of the superadobe mass construction.

Figure 14. Diagram for roofing system (Diagram by authors)

37. Construction Design Considerations

The monsoon season accounts for the vast majority of the years total rainfall in Senegal. With accesss to clean water and water security being such a poiniant issue in the region, as much water must be secured and stored properly during the season to be utiliased for the rest of the year. (Weather & Climate, 2019) Typical water collection systems are inadequite as the monsoon season can easily lead to overflowing downpipes and gutters, meaning that precous water is wasted or clogged pipes leading no water collection at all. As such the main method for water collection in our design is very large and durable cement gutter encourperated into the adobe structure. Rebar fixed into the earthbags and mesh layed across it acts as the core onto which the mass will be grafted. Packers are placed onto the inside edge of the gutter to prevent any overflow to the building's internal side. Rain will flow off the sheet metal roof into the gutter, where it will be collected into a superadobe cistern. Superadobe cisterns are a good water storage solution as they are reliable and combine all the positive qualities of superadobe.

The water system in total makes use of easy to build and maintain hand pumps. Electric pumps are often unreliable machines that breakdown or have parts fail. In the remote area of Baghere, there is no way to fix them as access to the expertise or parts required might not be avalible. Coupled with the local electric grid's tenuous nature, electric pumps are an unsustainable and unreliable solution that if dysfunctional could result in the inahbitants of the project going without water. There are many open source hand pump Figure 15. Detailed Wall Section (Diagram by authors) designs avaliable for developing countries to take advantage of that make use of easy to find and cheap resources, such as, wheels, timber or bamboo. There are a wide variety of types of pump avalible, such as wheel pumps and Kenya pumps that are designed to require easy and minimal maintnance without the use of potentially hard to find items such as lubrication. (McJunkin, 1977)

38. Construction Design Considerations

The water storage system utilises a combination of superadobe water storage, hand pumps, piping and irrigation equipment, all of which are able to be locally sourced and utalised. Rainwater is collected from the roof and then stored into a superadobe cistern next to the main building, which is locted on the lower part of the site. The water is then pumped via hand pump from the close cistern to another superadobe water storage at the elevated portion of the site, from which the water is then piped back to the Women's House, using the elevation of the storage to give water pressure to the project. This form of storage system requires no electricity, is easy to maintain, uses local resources and is easy to construct with local labour. Figure 16. Diagram of water system (Diagram by authors) Although manual labour is needed to pump water, once the elevated tank is full the Women's house will have easy access to clean water with little maintenance required.

39. Construction Design Considerations

This system is in conjunction with a greywater system where waste is then utilised in the landscape to further reduce water wastage and help provide the varous plants and food growing areas with much-needed water. This will help reduce food scarcity and provide appropriate accomodations for cleaning solutions. The cleaning method at the current moment in Baghere is simple stick and board washing, often without access to cleaning chemicals and with unclean water carried long distances. The water system provides an eco-friendly space where used water is not simply discarded after use and is brought to the user, conserving time and energy.

For human waste we have opted to use a humanure dry toilet system. Humanure composting toilet systems have a number of advantages. Firstly they do not require any single use items, such as plastics, which helps reduce costs and waste, they require no access to sewage systems or potencialy expensive elements such as septic tanks, and the end product is a clean and safe manure that can can benefit the onsite plantations. A humanure system uses an aerobic degrdation process, an overall easily managable and sustainable method for dealing with human waste. (Toilets for People, 2020)

Figure 18. Toilets for People Design Diagram (Toilets for People, 2020) Figure 17. Grey water principle diagram (Diagram by authors)

40. Construction Design Considerations

The not for proffit Toilets for People has a freely avalible humanure system that was created with developing contexts in mind. It has been utilised by NGOs across the globe and can be made on site with locally avaliable, cheap and sustainable materials. It is also able to be integrated into the superadobe walling system so that the airation and urine storage aspect of the toilet is not compromised. The aboveground design is also far more flood-resistant and easy to maintain than the typical ground system commonly used.

Figure 19. Toilet section diagram (Diagram by authors)

41. Construction Design Considerations

For lighting and energy, our project intends make use of a proprietry product from Sundaya, a modular solar powered lighting system with batteries and phone charging built in. This system is designed to utilised in developing contexts where there is no access to stable energy grids, and is intended to provide durable, safe and cheap solar lighting solutions. Sundaya products are readily avaliable and cheap in Senegal, and is sold thorugh one of the countries retailers, Total Gas Stations, which has a location near Baghere. This means that should any of the products fail, replacments can be found easily and the modular nature of the product means more can be added or taken throughout the project lifecycle. (Dalberg, 2013)

Figure 20. Sundaya Modular lighting Product (Sundaya, 2018)