Technical Information Research & Building Construction Analysis

Task 1

i. Construction Stages

Site preparation

In all construction and building projects, site clearing is the initial phase and it involves the removal of trees, vegetation, and old or unwanted structures that sit on the prospective site, as was the case in the observed project. In accordance with the statements of Wilkie (2011), all services including water, gas, and power were disconnected from the structure before the demolition work began. Other services like drainage and stormwater were also sealed off, and the necessary steps are taken to ensure that the nearby properties are protected. One of these strategies was to fence the site and ensure appropriate barricading to prevent unauthorized access to the construction site (Wilkie 2011). After demolition, the rubble was cleared and excavation work began.

Figure 1. Site preparation - demolition of the previous structure

Various equipment can be used in the excavation phase. The choice of equipment to be used depends on the nature of the specific site. For this specific site, site preparation and excavation was done using an excavator, semi-trucks, Bobcat, Vertical rammers, tippers, and plate compactors (Department of training and workforce development 2012). The operation of all the equipment was done by trained professionals to ensure safety for everyone involved and that work was done to the required standards.

Figure 2. Site preparation excavator

To ensure the site is completely level and that erosions and runoff are controlled, bobcats were used to level and grade the construction site. Grading is vital on a construction site for it helps to avert water flowing through the site and even for the foundation of a newly built structure. Grading in the current site was done by creating a slope away from the foundation of the structure (Department of Justice 2017). In addition, the ground was also leveled to ensure a perfectly level base for the foundation. Leveling was done using a builders auto-leveler, commonly known as the dumpy level.

Figure 3. Site leveled and fenced

Footings

The role of the footing is to carry the structure, form a base for the foundation, and to transmit the superimposed load of the structure to the ground. According to Wilkie (2011) and Department of Justice (2017), the type and the size of the materials should be proportionate enough to bear the load and suited to the condition of the soil. In the current construction project, excavation of the footings was done using an excavator. Piers were also used as the holes were dug using an excavator with an auger bit attached. Reinforced concrete was used for the footings.

Figure 4. Site preparation - excavator excavating for footing and foundation

After the footing, the slab was laid. A plastic sheet was used to function as the vapor barrier. The role of a vapor barrier is to prevent water from rising from the ground into the slab (Department of Justice 2017). The was in line with the AS 2870:2011 Residential slabs and footing standard clause 5.3.3.2(c) which requires that vapor barrier should be medium impact resistant. For the current construction project, a strip footing was sued that follows the structures walls, both external and internal. The footing thus uniformly distributes the load all through the structure. Both the strip footing and the slab have been reinforced with steel metal beams.

Figure 5. Site preparation - slab laid and wire mesh

In addition to the reinforced concrete used for the footing and the slab, waffle slabs were also used. The waffle slabs used where shipped to the site in prefabricated models. These were placed in waffle pods and connected using ribbed columns along the slab. Waffle pods consisted of equally spaced ribs with corresponding columns. A two-way ribbed system of waffle slab pods was reinforced with concrete cross-sections compromising of ribbed reinforcement, slab top wire mesh, voids depth and width, waffles slab thickness (Galeb and Atiyah 2011).

Figure 6. Site preparation - slab laying and precast Waffle slab

Floor

In the observed building project, piers were also used to support the concrete slab-and-beam floor. Pier holes were excavated along the location of the planned structure walls to carry the load of the structure and effectively carry it to the ground. The excavated piers had concrete poured to then a slab-and-beam floor system cast on the compressible void-former providing space for expansion of the soil (Standards Australia 2011). The piers were made of concrete and treated timber which was to an appropriate depth. The piers were then cut at the desired depth to allow for the casting of the floor.

Figure 7. Site preparation - pier holes

As required by the AS 3660.1, termite control systems were used in the current building project. In fact, various termite control systems have been used which include chemical control and physical barriers e.g. graded stone particles, and woven stainless steel wire mesh. The footing and the slab also have some termite prevention elements especially the use of a tight slab concrete.

A slab-on-ground type has been used for this structure. To make the slab firm and well anchored on the ground, adequately excavated beams are used. Waffle slabs that are placed near-ground level are also used with a grid of polystyrene foam as void formers that create a beams maze in between the pods (Standards Australia, 2011; Department of Justice 2017). Insulation, as is the requirement with conventional slabs, is placed beneath the floor panels, which is the current building is below the waffle slab pods.

An advantage of the current site is that is level, thus making it easy for lying of the various floor elements. After the ground was adequately compressed with a layer of gravel, plumbing was done, termite treatment done, then outside edge boards set. The entire area within the edge boards was covered with plastic sheeting, then a layer of wire mesh. Next was a layer of waffle pods and spacer placed in a grip pattern as specified in AS2870 (Standards Australia 2011). Steel reinforcement beams where then placed within the spacers between the waffle pods, and a wire mesh placed on the top. The top wire mesh and the reinforcement beam where fastened as required then concrete mix poured and adequately vibrated.

Figure 8. Slab laying - pouring and leveling concrete

The floor was finished by application of a thin top layer of colored cement and sand. The color varied from one room to another as per the plan, for example, a violet floor color was used for the bedrooms.

ii. Brief notes on observables in each of the photogrphs

Site preparation

Rumble waste products from the structures demolished during site preparation

Heavy duty machinery excavators used in demolition and earth excavation

Topography from the pictures, it is also possible to figure out the generally flat landscape and that it is highly vegetated with trees

Cleared and leveled site

Fence

Footing

Fence

Excavator

An excavated strip

Semi-finished slab made up of waffle slabs, wire mesh, polythene sheeting, and outside edge boards.

Flooring

Pier holes

Excavator fitted with an auger bit attachment

Top cement layer pouring

Cement and sand mixture

Men at work

iii. Hand-drawn sketches of footing and floor system

Figure 9. A sketch of footing and floor system (Adopted from Clarke 2013)

Task 2

Construction sequence for the footing and floor system

Footing

i. First, using the appropriate and available machinery, excavation is done to create a strip.

ii. Steel reinforcement bars are placed in proportion t the expected load and size of the planned structure...…system is a little more difficult to construct and takes more time (Smith et al. 2009).

Construction trades involved

Various trades are required for the successful and complete construction of both concrete floor system and a timber floor system. For the concrete floor system, the trades required include Carpenter who performscarpentry, building mainly with wood, a mason who builds with bricks and mortar, and a plumber and electrician to deal with piping and wiring respectively. In addition, laborers are required. On the other hand, timber floor system requires only a carpenter, a plumber and electrician, and laborers (Barrie and Paulson 1992; Olubunmi et al. 2014). In total, a minimum of five trades is required in concrete floor installation while only four trades are required to successfully construct a timber floor system.

Justification of the concrete floor system

The concrete floor system used in this building project is considered appropriate for the location with specific reference to the condition of the soil. Concrete floor system forms an adequate anchor for the structure especially in harsh weather conditions prone to cyclones. Given the wet nature of the soil, a concrete slab is best suited for it guarantees longevity. The longevity of concrete floor is more relevant in this area given the corrosive nature of the soil, even though it is slight. Moreover, the current building is a single storey which means it has a substantial load on the floor system. A concrete floor is, therefore, best suited to carry the weight of the building, especially the concrete footing.

Hand-drawn sketches for suspended timber floor

Figure 11. Suspended timber floor system