Key property components and how they fit together
As an astute buyer of property, you’re probably totally across key factors such as infrastructure, pricing, great areas and demographics, but there’s another line of knowledge you’ll find useful.
To make the most of your purchase, it’s advantageous to have at least a basic understanding of the key components of property. This information is particularly useful when it comes to your building and pest inspection or when coordinating property maintenance.
1. Base (footings)
1.1 Site preparation
The ‘site’ is defined by the boundaries and easements laid out on your title document. It will be further defined by any planning overlays or controls, which may limit the type of development that can occur. Site characteristics that will impact on construction include: slope, orientation, location, access, site amenities (e.g. view, vegetation, waterways), services (water, electricity, gas, sewerage) and geology.
Generally the site is cleared to within a metre of the external footprint of the proposed building. The site may need to be excavated—either bulk excavation (e.g. clearing a level area for a slab), or footing excavation (e.g. digging trenches or holes for strip and pad footings). On the basis of a site survey prepared by a qualified land surveyor, the position of the proposed building is accurately located on the site and pegged with markers.
Footings refer to the structure below the floor level, which rests on the soil. Foundations are the soil or rock state on which the footings rest. Isolated footings are pad, pole or pier type footings. These footings are separated from each other to provide a series of point supports. Continuous footings are strip or beam footings, generally a reinforced concrete footing system used in conjunction with masonry walls. Integrated footings are connected to a slab on ground system (referred to as a raft slab). Other integrated systems are pier and beam footing systems. Raft slabs are the most common form of Australian domestic footing system. Pier and beam systems are used when there is an inadequate foundation base near the ground surface.
1.3 Retaining walls
Inclined (or stabilised banking) walls are a type of retaining wall generally constructed from heavy (masonry) materials, at an angle. The wall elements interact with the fill behind to form a type of gravity retaining system. Gravity retaining walls are generally constructed of masonry and rely on their own mass for stability. They can have vertical, sloped or stepped faces or combinations of these. Cantilever retaining walls use reinforced concrete for additional stability. A horizontal element projected back into the earth at the base of the wall, that forms an L shape, assists in preventing the overturning effect. Generally, retaining walls should be designed by engineers, especially if they are supporting loads from adjoining properties or buildings.
The two common types of floor structure are concrete slabs and timber-framed floors. Concrete slabs include ‘slab on ground’ and ‘suspended slab’ types. Raft slabs (slab on ground) are generally laid over clean fill that has been compacted. Integrated edge beams and internal stiffening beams (areas where the slab is thicker) provide bearing points for load bearing walls (e.g. walls that carry the load of a roof structure or an upper floor. Drainage outlets (for showers, baths, basins and sinks etc) must be pre-laid under a slab on ground or incorporated into a suspended slab prior to pouring concrete.
For slab on ground, clean fill is laid over the excavated earth, compacted and formwork that forms the shape of the slab is installed. A plastic waterproof membrane is then laid over the fill and any drainage outlets that protrude through the membrane are sealed with tape. Steel reinforcement is laid within the formwork, tied together and held to the correct height by stands. The concrete is poured into the formwork on the plastic membrane. In some States the building surveyor must inspect the slab layout prior to pouring.
A traditional timber-framed floor system involves stumps, bearers and floor joists. Stumps can be timber or steel, which are cast into concrete footings. Other types of timber floor systems involve supporting walls with isolated footings located directly below. A platform timber-framed system is where the internal walls are not directly supported by the footings and so footings are laid out on a regular grid.
3.1 Timber wall framing
In domestic construction, generally the timber used for wall framing is machine graded pine (MGP). Walls are constructed using rectangular sections of timber called studs (vertical elements), bottom and top plates (horizontal elements), noggings (horizontal bracing elements between studs) and cross-bracing (generally a metal strip). Sheet material can also be used for bracing. In post-and-beam construction, a series of vertical posts that form part of the wall structure support a grid of beams that forms part of the roof structure.
3.2 Brick veneer construction
Brick veneer construction is basically timber-framed construction with a brick or block external skin. The structural loads are taken by the timber frame, with the brick/block work skin being tied back to the timber frame for stability. The masonry skin requires either a continuous footing (strip footing) or a slab on ground to provide the base.
3.3 Masonry construction
Often referred to as cavity-brick construction, this approach commonly involves two single skins of load-bearing masonry with a cavity in between. Masonry can be clay, lime silicon or concrete bricks or blocks. It requires either a continuous footing (strip footing) or a slab on ground to provide the base. Internal walls are usually single skin and are built directly onto a concrete slab, or footing if using a timber framed floor system.
Non-habitable buildings, such as garages and sheds etc, will generally use a single skin of load- bearing masonry (which can be treated to ensure weatherproofing if the walls are external).
3.4 Concrete panels
There are two main types of concrete panel construction: precast (cast off-site concrete panel walling), and tilt-up (cast on-site concrete panel walling). Concrete panels can also be cast with insulation sandwiched between two layers of concrete—these are called sandwich panels. Concrete panels are not common in residential construction and are used more for commercial construction.
The advantages of concrete panel walling include: speed of construction, reduced requirements for scaffolding, good acoustic, thermal and fireproofing performances and good quality control. Precast concrete panels are reinforced panels cast horizontally in moulds in factories and are fixed to a steel frame or cast on-site concrete columns. Generally the panel thickness is between 150 and 250 mm. Tilt-up concrete panels are panels cast horizontally on site in a casting base (formwork) and then lifted or tilted into place. Panels can be cast one on top of each other to save space. Generally the panel thickness is between 150 and 250 mm. Tilt-up panels are restricted to two or three stories.
Generally, concrete panels are load-bearing and rest on a floor slab, supported by continuous strip footings or isolated footing systems and are tied together by steel cleats that are cast into each panel. Concrete panel walling can also act as a retaining wall.
The elements of a window include the frame, the glazing system and the opening system. Window frames are commonly made from timber or metal (generally aluminium, although in the 1950s steel-frame windows were common). Plastic (uPVC) window frames are now available.
There are different types of glass available that will influence both the amount of heat that is lost or gained through windows, and the amount of daylight that is allowed to enter. A reflective glass will reduce the amount of light entering but may cause problems for the surrounding buildings. Double glazing and/or high-performance glass provides a higher level of thermal control than single glazing, with little loss of daylight transmission.
Windows are commonly described by the way they open. Windows without an opening system are called fixed windows. The part of the window that moves to open is called the sash. Operable window types include: horizontal sliding, awning (hung from the top), casement (hung from the side), double hung (where the top and/or bottom sash slide down/up), louvre (a series of glazed panes that open as one unit) and hopper (bottom hung).
Since 2004, the Building Code of Australia (BCA) has required external windows to achieve minimum energy efficiency ratings to reduce heat transfer and solar heat gain. The minimum rating will depend on the climatic zone (location of the building), the orientation of the window (north, south east or west) and whether the window has any shading devices such as awnings or sun blinds etc.
There has been a system established to rate the ability of a window system (includes frame, glass type and operable system) to prevent heat loss or gain. Windows can now be given an energy rating under the Window Energy Rating Scheme (WERS). The more stars a window achieves, the more resistant it is to heat gain and loss. Information is available on the WERS website at <http://www.wers.net>.
The BCA also requires that all external windows are fitted with adequate seals to prevent heat loss or gain into or out of the internal spaces of the building.
Doors are commonly described by the way they open, for example, swing doors, sliding (surface mounted) doors, cavity sliding doors, or bifold doors. Doors 0n external walls should be weatherproofed and solid core, whereas internal doors can be hollow core.
The BCA also requires that external doors are fitted with adequate seals to prevent heat loss or gain into or out of the internal spaces of the building.
6.1 Roof type
The different roof structures are shown below.
6.2 Roof structure
Conventional roof framing generally involves pitching rafters off the top plate (horizontal element at top of wall). The walls take the load of the roof. Typical roofing structural elements include ceiling joists (span between load-bearing walls and provide lateral support); rafters (pitched from the top plates, run in the same direction as the roof cladding, generally fixed at the apex to a ridge beam); underpurlins (horizontal members that run at right angles to the rafters and help support the roof loads); struts and props (attached to the underpurlins transfer loads to load-the bearing walls below); collar ties (horizontal members attached between rafters on opposite sides of the ridge brace rafters to prevent spreading); ridge beam (ties rafters together at apex); hanging beam (spans between load-bearing walls to fix ceiling joists to and support ceiling loads); and roofing battens (attached to top of rafters to provide fixing for roof cladding).
Trussed roofs comprise a series of engineered trusses designed to span long distances between load-bearing walls. They are rigid structural frames that are easy to erect and incorporate all roofing members. As they span between external load-bearing walls, they allow flexibility in internal planning.
Flat, skillion, or vaulted roofs are generally post-and-beam construction. This type of roofing structure has no attic space. Roofing and ceiling lining are fixed either side to the roof structure.
Services are a very important part of a property. This section explains key aspects of services relating to most property types.
7.1 Drainage: Stormwater
Sub-surface stormwater drains are generally required to redirect surface and subsurface stormwater away from a building and includes the following components.
- An absorption trench – which is a strip excavation located across the path of the water flow (i.e. on the higher side of the dwelling) with an agricultural drainage pipe (a perforated pipe) sitting in a bed of crushed rock, covered with a layer of coarse sand and a layer of topsoil. The agricultural drainage pipe falls towards the stormwater disposal system.
- Water filters through the material in the excavated strip and is gathered by the ‘agi’ drain and dispersed to stormwater.
- The collector system is the roof’s drainage system. It includes gutters and downpipes that can be connected to a rainwater tank (with an overflow to the mains stormwater system) or directly to the mains stormwater system.
- The stormwater disposal system is a separate system from the sewerage disposal system (see below). Stormwater is generally discharged with minimal treatment to waterways or directly to the sea.
7.2 Drainage: Sewerage
The sanitary outlets that are usually connected to the sewer system include: toilets, hand basins, showers, baths, laundry troughs, washing machines and kitchen sinks. Water from the toilet is known as blackwater. Water from all other fittings listed above is known as greywater. It is becoming increasingly common for showers, baths, hand basins and some laundry water to be connected to a greywater re-use system.
Liquid waste is drained from buildings and removed via piped infrastructure (sewer mains) to a remote treatment plant. After treatment in that plant, water is discharged to the sea or, increasingly, re-used for non-potable (not for drinking) water requirements.
A septic tank system is an on-site treatment system for areas with no reticulated sewerage system. It requires an area for dispersal of treated water and maintenance (emptying) every five years.
Cold water is brought onto the site from the reticulated water supply, through the water meter and then dispersed to the cold-water supply points within the building via copper or plastic piping. Hot water comes from cold water that has been reticulated though the hot water system/s and then dispersed to hot-water supply points within the building via insulated copper piping.
There are two common types of hot-water systems: storage and instantaneous. Storage units store hot water for immediate use in an insulated container. Instantaneous units heat water as it is required. Hot- water units can be powered by electricity, gas, wood or solar energy.
The gas supply is connected and laid by the plumber. Natural gas is obtained from a reticulated town supply. LP gas is used where there is no town supply and is contained in storage tanks that are delivered to individual sites.
Normally the power authority will provide power supply up to the point of entry into a building (i.e. the meter box). It is then the responsibility of the building owner to distribute the electricity via a switchboard to all power and lighting outlets. All permanently wired appliances and fittings (such as ovens or heaters) require special installation.
It is becoming increasingly common for buildings to have sophisticated communication or electronic control. There are two aspects to these systems. One relates to the data or communication cabling— locating data outlets (phone, fax, internet) throughout the house to enable connections and networking. The other approach, commonly called home automation, involves the connection of electrical appliances and fittings to a central control system and the linking of audio-visual equipment.
With the government desire to reduce energy use in buildings it is common for a building’s electricity to be supplied through photoelectric solar cells. There are incentives provided by the government in the way of rebates for owners who install photoelectric solar cells. It is also possible to sell back power to the main grid.
7.5 Mechanical (heating and cooling)
The most appropriate heating system for a dwelling depends on a number of factors such as the size of the dwelling, its orientation, the number of rooms to be heated and the length of time heating is required. There are two types of heating—radiant (radiates direct heat) and convective (circulates warm air).
There are two main types of heating systems—central and space heating. Central heating is generally less efficient as it heats the entire dwelling. Space heating heats individual spaces. Examples of central heating systems include ducted-air, hydronic and electrical slab-heating. Examples of space-heating systems include gas portable and fixed heaters, electric portable and fixed heaters, wood stoves and open fireplaces.
Cooling can be provided by fans, evaporative coolers or refrigerated coolers (air-conditioners). Fans provide cooling by circulating air and causing evaporation off the skin. Evaporative coolers cool the air by passing it over water. Air-conditioners use a refrigerant to chill water, which is then used to cool air.
Air-conditioners can also be reverse cycle and be used to heat buildings. Ducted systems can also be designed to operate in zones enabling different parts of the building to be condition thus using less energy. It is important that buildings are adequately sealed to prevent hot air leakage.
8. Fixtures and fittings
The quality of fixtures and fittings can affect the value of a property. When selecting an investment property, with the intention of renting it out to tenants, it is important to be aware of the quality of the fixtures. If they need to be replaced, this cost should be included in the calculations of profitability of the investment.
Fittings in an existing property can be taken away by the vendor, so it is important to ascertain which fittings are included in the purchase contract and which are not. A tenant will expect curtains and floor coverings, a stove and lighting, so if the vendor is removing any of these, you need to factor in replacement cost. Appliances may need to be provided for a furnished apartment, but otherwise it is likely that removable appliances will be the responsibility of the tenant.
Fixtures are items that are permanently ‘fixed’ into a building and cannot be removed without damaging the property. Fixtures can include the following:
- Bench top stove
- Wall oven
- Waste disposal unit
- Joinery (including wardrobes, cupboards, benches, shelves and drawers)
- Ducted air-conditioning and fixed heating and cooling appliances.
Fittings are appliances and equipment that are not permanently fixed to the building and can be removed without damaging the property. Fittings can include the following:
- Freestanding stove / oven
- Microwave oven
- Washing machine
- Clothes dryer
- Garden ornaments.
Appliances are now being rated for their energy and water efficiency. The National Energy Rating Scheme mandates the following appliances to carry an approved energy label:
- Clothes washers
- Clothes dryers
The following products also have Minimum Energy Performance Standards (MEPS) that must be met:
- Refrigerators and freezers
- Water heaters
- Electric motors
- Ballasts (used to to limit the amount of current in an electrical circuit)
- Commercial refrigeration.
All appliances that use water are now required to show their water efficiency. The same is required for water fixtures such as tap fittings and sanitary ware (toilet bowls, cisterns and similar items). The water efficiency of products is shown by an ‘A’ rating on a label at the point of sale. Reference :Water Services Association of Australia, <https://www.wsaa.asn.au>.
Products currently covered under the scheme include the following:
- Shower heads
- Toilet suites or matching cistern and pan sets
- Clothes washing machines
- Taps and tap outlets
- Urinal operating mechanisms
- Flow regulators.
The information above provides a basic overview of key property components. The information above was compiled from a combination of reference material written by the Property Investment Professionals of Australia, Wilkie, G. & Arden, S. 1984, Building Your Own Home: A Comprehensive Guide for Owner Builders, Lansdowne Press, Sydney, NSW; ArchiCentre.
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Crave Property Advisory is a unique property strategy and buyers agent service. As the only independent and unbiased advisory that can help you use any property strategy Australia-wide, Crave’s services extend to home, investment and commercial property. A highly client focused organization, Crave developed the Modular Investing System (MI System) to provide clients with the ability to use a tailored mix of strategies and efficiently build profitable portfolios that create lifetime income.
Debra Beck-Mewing is the CEO of Crave Property Advisory, and has more than 20 years’ experience in property investing, Australia-wide. She has used a range of strategies to build her property portfolio including renovating, granny flats, sub-division and development. Debra is skilled in identifying development opportunities, and sourcing properties that have multiple uses and multiple exit strategies. She is a Qualified Property Investment Advisor, licensed real estate agent and also holds a Bachelor of Commerce and Master of Business.
Disclaimer – This information is of a general nature only and does not constitute professional advice. We strongly recommend you seek your own professional advice in relation to your particular circumstances.
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