When one wants to construct a house he must first look into the cost of building the house, which entails its affordability, energy efficiency, durability and the quality.
Recent construction methods are always bent on being energy efficient and also being less harmful to the environment. One should take a lot of consideration when making a choice on what kind of house they want to build to increase their comfort and also reduce the undue stress on nature.
The physical location of the building should also be taken into consideration for the plan and the materials to be used will greatly be affected by the location of the house.
The most important thing in a building is its foundation. For the building to be stronger with minimum movement, the soil bearing capacity must be taken into consideration. This varies from place and some places have a higher soil bearing capacity than other places thus the need of consultation from qualified geologists or engineer. The soil bearing capacity can be naturally altered by building works that may have taken place in the site. For the required soil bearing capacity to be got, the soil is consolidated through compaction. The site must also be classified to prevent cracking of walls and prevent building failure.
After the site has been classified the land is cleared of the bushes and the trees some trees may be left for the landscaping of the completed building. Roots stumps, tree limbs, underground wood, rocks to a distance of approximately three meters from the building zone should be removed. If the top soil is of good quality, remove it with a bulldozer for later use in landscaping. The two types of excavation used are;
Bulk excavation. This is where a bulldozer is used to clear a level ground for the building.
Footing excavation. Here the bulldozers are also used but using the back-hoe or it’s shovel in order for excavation of the footing according to the plan of the house.
The excavation for the base or the foundation of the house should be done taking into consideration the following factors. For flat sites, generally level but may slope not more than 1:40 to allow excavations to drain and sloping sites at an angle of not more than 1:10.
When making the slab for the footing the following methods that mainly depend the slope of the site, may be used. These methods include:
Strip and pad concrete footing
When using this kind of footing the trench should be cleaned and the sides properly squared and well placed to accommodate the walls to allow even bearing of pressure. In case the trenches are not square, (mainly caused by excavation of rocks or the nature of the foundation) an extra concrete is allowed on this beam. For this will lead to an extra cost, it can be avoided by properly preparing the trenches the first time. Strip footings are toughened with a cage of reinforcement. The reinforcement consists of; top and bottom bars or trench mesh with connecting bars called ligatures. These are spaced at not more than 1200mm or as specified by the engineer. The top and bottom bars are spliced as a requisite to form a continuous reinforcement with a minimum lapping of footing reinforcement 500mm. The edges and intersections are to be fully lapped at their intersection. Reinforcement to footings is to have a minimum of 40mm cover of concrete on all sides, this can be ensured on the bottom by the use of wire or plastic bar supports or the reinforcement can also be balanced in the trenches by wire ties fixed to timber hangers on both sides of the trench.
The pad footing is usually used in combination with the strip footing in a bearer & joists intended dwelling. The pad footings are required to hold up piers that will sustain the floor loads. These footings must be constructed in concrete except that masonry footings can be used under masonry piers. The footing must be enlarged by 50mm or excavations filled with tamp soil.
Pier and Beam footing
This method is used in circumstances where the foundation material over the buildings envelope is of either highly reactive or poor load carrying capacity. The piers are bored to a depth that ensures that all of the building is holdingon the same foundation material. The footing beams that span between thepiers are considered so that they will support the structure with no direct bearing on thebase material, the footings bearing must be on the piers only.
Footing failure can be caused by; Unstable back filling of cuts and fills, incorrect reinforcement, excessive vibration on concrete, poor site drainage and when excessive water is added to the concrete before placement.
Slab on ground
This type of slabs is only suitable on certain sites and not all the sites and alternative methods can be used to employ concrete slabs on sloping sites. The following construction procedures should be followed;
The vegetation should be cleared from the site.
The soil under the slab should be kept dry.
The slab should be designed to go with the soil classification.
Compact the soil under the slab to ensure the fill is retained.
Place the membrane that is waterproof and with a minimum thickness of 0.2mm before placing the slab then treat the under-slab against penetration by termites (should meet AS3660.1 or as amended). Fully tape around all pipe penetrations.
The surface of the slab should protrude 150mm minimum above finished ground level, except in sandy, well-drained areas where the minimum height shall be 100mm. These heights can be reduced locally to 50mm near adjoining paved areas that slope away from the building.
Suspended slab on fill
This slab is created to extend between supports. In this method of construction the slab is supported on top of the base walls rather than between them. The fill is used to provisionally support the slab. The fill is generally of poor quality material and should be compacted before covering with a moisture barrier. The fill will settle away from the underside of the slab with time, however, as the slab is designed to be suspended, the result is a simple to construct concrete floor in which all the building loads are transferred to the footings. These are only used when on ground floor slab where 600mm is the height from the ground to the underside of the slab.
Inclined or stabilized banking
It is a gravity retaining wall constructed from bricks, concrete blocks and stones but interlocking precast concrete or hardwood can be used. Here the backfill is deposited inside the interlocking crib structure and acts integrally with the crib structure to form the gravity retaining wall.
Gravity retaining wall
These are commonly used in domestic wall constructions. They largely depend on their own mass to resist the upending forces exerted on them. Gravity retaining walls can be constructed out of almost any masonry units’ poured concrete. These walls are generally well attached and bedded on filling courses, but it is possible to construct them using dry laying techniques mainly when natural stone is used. It is economical to use the reinforced concrete.
Cantilever retaining walls
They use reinforced concrete for extra strength poured in place, purchased as precast units or by reinforcing manufactured concrete masonry blocks. The wall thickness can be reduced significantly but the base to height ratio can remain at the 3:1 range.
Energy efficient housing
One should consider the orientation of the housing for the effective cooling of the house and also for the positioning of the solar panel. The positioning will also influence the landscaping of the house for beautification.
Some modern methods of construction
Open Panels – involves the construction of skeletal structures only while other panels are manufactured in the factory and later assembled on site. These panels may be made from timber, steel or structurally insulated panels.
Closed Panels – this is more complex for it involves a higher degree of prefabrication of the doors, windows internal decorations and installations.
The panelized methods of construction are more flexible than the volumetric systems for they can accommodate variations in the design and the unit plan. Panelized systems can be piled flat which leads to more effective transportation to site.
Volumetric Construction entails the construction of three dimensional structures that are manufactured in the factory conditions before transportion to the site. Modules can be brought to site in a variety of forms and can be empty shells or fully complete with services, internal features & external finishes.
Hybrid and Pods
Hybrid methods combine both panelized and volumetric approaches. Areas that are typically highly service or more repeatable, such as kitchens and bathrooms, are fully fitted out with all sinks, sanitary ware and tiling, ready to be plumbed in and are finished using a panelized method.