3.2 CONSTRUCTION PROCESS

- Roof materials Selection of roof materials based on the structure and materials’ characteristic of walls and foundation, also needs to follow the climatic and temperature conditions in local. The purposed building located in tropical zone, the most important consideration in design stage is heat dissipation and ventilation. Besides, due to the material selected for walls is brick, we would like to reduce the weight of roof as much as possible for matching up the load-bearing capacity of brick walls. Timber structure covered by aluminium sheets is the combination we select for roof. The timber type for the structure is pine. Although pine is not the main species of plants in local, it is common on local timber market and the price is lower than precious timber produced in local. Besides, lumber is another available option. Lumber is the timber recycled from old building, furniture or other woodwork. Effective utilization of lumber can reduce deforestation and control desertification . In terms of roof sheet, our choice is aluminium. Aluminium is a lightweight material with good ductility and heat dissipation performance. Under the same volume, weight of aluminium is only one-third of iron or steel. In addition, good ductility makes it easier to satisfy the requirements of different kinds of construction project. Therefore, it is popular in Senegal and many other African regions.

3.2 Construction Process

Construction process of the women house is similar to the detached houses in local. It can be divided into five main steps: site clearing, foundation construction, wall&column construction, roof construction and landscape construction.

- Site clearing: The site needs to be cleaned up in order to eliminate obstructions that might affect construction process before construction works start. According to the Standard Method of Measuring Building Work in Africa, Site clearance work includes Digging up and removal of rubbish, debris, hedges, shrubs and trees not exceeding 200mm girth.

- Foundation construction: The foundation type we selected for the purposed building is concrete strip footing. The concrete strip footing consists of three components: concrete casting layer, brickwork and ground beams.

The first step is trench excavation. For a single-storey building, the depth of foundation trenches needs to reach 0.8m at least. Position of trenches shall be coincident with walls on the architectural drawings because the footings are used for supporting walls and transferring load from walls to the ground. According to the regulation of construction standard method in Africa, excavated material should be set within 100m from the perimeter of the excavations for use as filling and landscape construction.

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During trench excavation, workers can make column reinforcement. The column reinforcements are assembled by iron rods and shall be fixed at the bottom of trenches. They are the skeleton structure of columns and used for increasing strength of columns.

The next step is concrete making. Raw materials include cement, pebbles, sand and water. These materials shall be mixed into concrete proportionally.

After concrete making finished, we can start to pour the concrete into trenches. Concrete needs about 4-5 days to reach 100% stress after pouring.

Subsequently, sand layers and concrete slab shall be set up. Filter fabric attaches to the concrete slab and provides waterproof for the foundation.

Lastly, the whole foundation should be cast by concrete in order to form a flat surface for walls and other structures above the ground. The foundation work shall be finished after the

Fig.12 Foundation preparation (L) & Filter fabric laying (R)

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concrete set.

- Walls After finishing foundation construction, the next crucial step is walls’ construction. The construction process of single brick wall is relatively simple, and it is a fairly quick process. The supervisor needs to pay close attention in the whole process for ensuring that the walls are straight and the angles are correct. It is the most important point in this stage.

Once the walls’ brickwork is finished, casting of columns shall continue. The iron skeleton of columns has been fixed with the concrete layers of foundation and the casting work means encasing the iron structure of columns with concrete. Finished columns shall become one flesh with brick walls so that columns can provide strength and reinforce walls, also support the roof structure.

Fig.13 Concrete foundation

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In addition, lintels for windows and doors need to be set following the building process of walls for supporting the load from structure above.

- Roof We designed a sloped roof in order to drain water away and collect rain water. Timber columns is necessary outside the external walls for supporting the roof and the construction of the pillars shall be finished before roof construction. Therefore, the construction process of roof shall be as follow: First, excavate holes for fixing pillars

Second, raise and anchor pillars on the ground outside the external walls.

Third, raise short timber pillars on the top of inside external walls and connect these short pillars with columns inside the internal walls.

Fig.14 Brick walk

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Subsequently, build longitudinal beams spanning the internal and external pillars.

The next step is installing transverse beams spanning between each two adjacent beams. Finally, cover aluminium sheets on the top of roof skeleton structure and fix it.

The connection method we select for roof timber components is dovetail connection. Dovetail connection is a traditional wood connection which is commonly used in timber structure construction. A series of 'pins' cut to extend from the end of one rafter/strut interlock with a series of 'tails' cut into the end of another timber component. Dovetail connection method is one of the strongest timber connection method.

The connection method for roof sheets is welding joint. Welding joint means using spot welding technology to connect adjacent elements. Workers shall reserve several solder joints on aluminum sheets and melt the sheet material to complete connection. Welding joint is a relatively simple method and does not need any pre-process. Therefore, it is a proper method for the purposed building.

Fig.16 Structure connection detail

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