Small Building Construction: Site Preparation, Foundations and Footing

SITE PREPARATION

The above picture is of a device named total station, it includes a tripod and a theodolite. A theodolite is a telescope that measure angles in both the plane, horizontally as well as vertically. Total station is a device which is manually used to read the distance meter of any slope. This device is used by land surveyor, and it also determine the condition of the soil. The step is taken to determine soil bearing and soil stability of the site. We can also analyse the fixing of underground services, drainage and also the water level of ground.

This the corners and boundaries of the structure to be built. This is the second step of site preparation.  This is done to locate the building on the given piece of land. Spray paints and pegs are used to done the marking. A string line is run through the structure as a mark-up. This will help in placing the masonry or brick or of concrete blocks. This will also determine the concrete level of the site. CLEARED FROUND LEVEL(CGL).

Once the site is prepared, the next step is to set up the boundaries. And for doing so the top soil is been removed. The removal of top soil or clay is done using digger, this asset the level using a dumpy level against the datum point until it gets the desired level according to the plan of the building, which comes to an approx. of ¾ th of land. The image is the setup of the building, so as to fit the design into the real 1:1 scale. As it is the foundation of the structure it needs to be accurate. The safe distances as required for the building are given in the NEW ZEALAND STANDARD CODE BOOK 3604,2011 CLAUSE 1.2(B).

The image describes state the removal of soil so as to start the concrete foundation of the building. This is the first step of the foundation, which includes the connection of the structure to the ground, which will transfer the loads. These are deep holes. The foundation describes how stable the building would be, so the weight is distributed to avoid the overloading of the soil. This step is important because this process will avoid the building to get demolish if any natural calamity occurs as the building would be stable enough to outstand the calamity.

FOUNDATIONS

The picture is a plan view of the foundation work to be done on the site. A plan is a view which is represented horizontally, it looks similar to map (in common word), but has detailing of the work or the site. The picture is describing the masonry veneer foundation edge detail, which is consist of clay brick veneer along with the joints installed on the foundation with a cavity with is about 60mm. These veneers are absorbent and water can easily pass through this. This masonry veneer is also known as wet cavity system. The bottom of the cavity footing and the front of the concrete slab are water resistance, so this avoid the slab to absorb water. Masonry veneer system support foundation according to NZS 3109 or NZS 4229 Foundation: those parts of a building, transmitting and distributing loads to the ground through a footing. (NZS3604,2011). First the plan is been set and then accordingly the work is been executed.

After the plan is been set, the real work begins. The picture is of the footing which is done on site. FOOTING: that portion of a foundation bearing on the ground and any adjoining portion that is reinforced so as to resist forces. A footing may be spread out to provide an increase in bearing area or an increase in stability (NZS3604,2011). Standard footing according to NZS 3604 is 300 x 300 footings 300mm depth with 2/D12 bars and D10 starters @600ctrs. The digging for the footing is been done using small digger. And then the frames are been set later. And later the iron rods are been set out into that.

After the frames are the set, concrete is poured into the space made. While pouring concrete air bubbles are formed and to remove them a reinforcing rod is been circulated. To smooth concrete at the top of foundation concrete trowel is used, and the level of concrete filled is checked continuously so as to ensure the setting of concrete level of the foundation.

Once the concrete is poured, it is left to get set. The concrete is left to stiff. The setting time of concrete is generally 24-48 hours. During the time it get harden, water is sprinkled on concrete so as to maintain the temperature and to avoid cracks. Here in the image the concrete is harden for the footing.

The picture describes the spreading of concrete on footing. The reason to spread concrete all over is to put the equal amount of concrete all across the site are. This will create a stable level, and so the next step of construction of building would be taken into action.

FOOTING

In every building or house the flooring is done with concrete. So now to make a concrete slab framework for the building is been done. The above picture shows the framework is been completed, using wooden as a material. The next step would be the construction of the wall. This foundation walls are been constructed by concrete blocks. This is also known as concrete masonry.  In the above picture the perimeter of the site is been framed. The main purpose of doing concrete masonry is to raise the ground level of the building. The concrete blocks are put together by using the adhesive known as mortar. FOUNDATION WALL: the part of the foundation comprising a concrete masonry or concrete wall supporting a building or part of a building, and not extending more than 2m above the underside of the footing. (NZS3604, 2011).

This picture is again showing the frame work done for the construction of the floor. The concrete blocks are been laid together to construct the wall. And the underground services like water, sewer, electrical and drainage are installed all across the building as per the plan by making void in the constructed concrete walls. Later the footing is dug. It is ready to take on the next step.

Once the footing is excavated, the frame is made around the perimeter of the building, sand is filled into it. The reason of doing this is to increase the level of the building. Later this sand is compressed. In the given picture the black polythene of about 0.25mm thick is been laid over the sandy surface. This is done to prevent moisture to enter the concrete blocks of the building. Now the next step is to pour concrete and make a concrete slab. NZS3604 section 4.5.4.1 states every slab on the ground floor shall incorporate a continues DPM between the ground and floor surfaces beneath the concrete ground slab. This prevents moisture travelling up through the concrete into the building meeting requirements of NZS3604 section 7.5.4.2. DAMP PROOF MEMBRANE(DPM). A sheet material coating or vapour barrier, having a low water vapour transmission, and used to minimise water and water vapour penetration into buildings. Usually applied against concrete in contact with the ground. (Also known as a concrete underlay) (NZS3604, 2011)

The above image shows the concrete slab. Once the polythene is placed, concrete is poured. Concrete is a mixture of cement, water, aggregate and adhesive. The concrete strength is determined by the mixture and the setting NZS3604 clause 4.2 states that concrete in zone c must be 20Mpa. After the concrete is poured the air bubble are been removed and it is left to set. While the concrete is settled down it is been made wet with water over time to time so that it does not form crack in it. This is the way the concrete slab for flooring is been made.

REFERENCES

1. https://www.jurovichsurveying.com.au/faq/what-is-a-total-station
2. https://www.powerblanket.com/blog/long-concrete-take-set/
3. NZS 3109
4. NZS 3604, 2011
5. NZS 4229