Building Construction Analysis: Footing, Floor & Site Prep

Site Preparation and Excavation

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

Various equipment can be used in the excavation phase, and the choice depends on the nature of the specific site. For this project, site preparation and excavation were carried out using an excavator, semi-trucks, a Bobcat, vertical rammers, tippers, and plate compactors (Department of Training and Workforce Development 2012). All equipment was operated by trained professionals to ensure the safety of everyone involved and that work was completed to the required standards.

To ensure the site was completely level and that erosion and runoff were controlled, Bobcats were used to level and grade the construction site. Grading is vital on a construction site because it helps to avert water flow through the site and provides a stable base for the foundation of a newly built structure. Grading on this site was achieved by creating a slope away from the foundation (Department of Justice 2017). The ground was also leveled to ensure a perfectly level base for the foundation, using a builder's auto-level, commonly known as the dumpy level.

Observables — Site Preparation:

Footing System Construction

The role of the footing is to carry the structure, form a base for the foundation, and transmit the superimposed load of the structure to the ground. According to Wilkie (2011) and the Department of Justice (2017), the type and size of 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 carried out using an excavator. Piers were also used, with holes dug using an excavator fitted with an auger bit attachment. Reinforced concrete was used for the footings.

After the footing, the slab was laid. A plastic sheet was used as a vapor barrier to prevent water from rising from the ground into the slab (Department of Justice 2017). This was in line with AS 2870:2011 Residential Slabs and Footings, clause 5.3.3.2(c), which requires that vapor barriers be medium impact resistant. A strip footing was used that follows the structure's walls — both external and internal — thereby uniformly distributing the load throughout the structure. Both the strip footing and the slab were reinforced with steel beams.

In addition to the reinforced concrete used for the footing and slab, waffle slabs were also incorporated. The waffle slabs were shipped to the site in prefabricated form, 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 comprising ribbed reinforcement, slab top wire mesh, void depth and width, and overall waffle slab thickness (Galeb and Atiyah 2011).

Observables — Footing:

Floor System Installation

Piers were used to support the concrete slab-and-beam floor. Pier holes were excavated along the location of the planned structural walls to carry the load of the structure and transfer it effectively to the ground. The excavated piers had concrete poured into them, and a slab-and-beam floor system was then cast on a compressible void-former that provides space for soil expansion (Standards Australia 2011). The piers were made of concrete and treated timber, set to an appropriate depth and then cut at the desired level to allow for the casting of the floor.

As required by AS 3660.1, termite control systems were employed in this building project. Multiple termite control methods were used, including chemical treatment and physical barriers such as graded stone particles and woven stainless steel wire mesh. The footing and slab also incorporated termite prevention elements, most notably the use of tight slab concrete.

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

Because the site was level, laying the various floor elements was straightforward. After the ground was adequately compacted with a layer of gravel, plumbing was installed, termite treatment was carried out, and the outside edge boards were set in place. The entire area within the edge boards was covered with plastic sheeting, followed by a layer of wire mesh. Waffle pods and spacers were then placed in a grid pattern as specified in AS2870 (Standards Australia 2011). Steel reinforcement beams were placed within the spacers between the waffle pods, and a wire mesh layer was placed on top. The top wire mesh and reinforcement beams were fastened as required, then concrete mix was poured and adequately vibrated. The floor was finished by applying a thin top layer of colored cement and sand, with the color varying by room — for example, violet was used for the bedrooms.

Observables — Flooring:

References

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