Choosing and using a site

Once you have chosen the general location for your home, you can look at specific sites and decide whether they are right for you.

Size and shape

Note the size and shape of the block:

• Is it large enough for your needs? Remember that all the features you want as part of your lifestyle do not necessarily need to be provided in your home. For example, access to nature and green space can be provided by a nearby park rather than a large garden.
• Is it a standard rectangle, or something else? Different shapes might add to the interest of the block, but they may require adjustment to the design of your home.
• Does it contain easements? Remember that maintaining access to easements is usually a requirement on the title of the property, therefore building on or over an easement is usually not permitted. Some easements can be quite large and restrict the placement of your home on the site.

Climate suitability

Find out what building designs will suit your climate and see whether your site can easily accommodate them:

• Note the orientation of the block. Ensure that the opportunities for solar access or cooling breezes are appropriate to the climate.
• If buying a block in an estate or subdivision, consider the solar orientation of the block relative to other blocks. Make sure you can enjoy views and maximise access to winter sun and summer breezes (or in tropical climates, shade and cooling breezes) without compromising privacy.
• Observe how the site terrain and vegetation affect air movement and solar access.

Surrounds

Consider how future developments and buildings nearby might affect your home:

• If adjacent blocks are empty, are the blocks wide enough to prevent overshadowing and overlooking? Shadow impact is influenced by latitude, and height and spread of trees, and may affect the way you should site your home.
• Is there a potential for loss of privacy and increased noise from neighbouring areas?
• Will there be heat- or ventilation-related effects from adjacent developments?

Also check how your local microclimate is affected by the surrounding area. For example:

• coastal – sea breeze or land breeze effects, which moderate regional extremes; storm exposure
• flat open country – subject to accelerated wind speeds; minor changes in topography can have significant effects
• woodlands and forests – differential solar access and airflow; higher humidity
• valleys – differential solar access and temperatures dependent on location and elevation
• built-up neighbourhoods – elevated ambient temperatures; differential solar access and airflow; increased turbidity of wind.

Topography

Consider the natural topography of the site, and how that might affect your house design:

• Check the slope of the site, and consider whether special measures will be needed to deal with a steep slope
• Design or choose your house to respond to the natural topography of the site.
• Minimise the use of excavation and fill to save energy, preserve natural drainage patterns and prevent soil erosion. Excessive excavation can damage the ecological integrity of the site and disturb groundwater zones.
• Stormwater, particularly overland flows, can create severe problems. Before buying, check that the site is not affected by stormwater entering from neighbours’ gardens or downpipes.

Geology

The underlying geology of the site will influence construction costs and energy used in excavation. Investigate the geology and topography of the block:

• What sort of rocks or soils are present? Is there a problem with salinity? Is there a threat of landslide, soil slip or creep?
• A geotechnical report is often required by your local council or your engineer. If in doubt, obtain one.
• Identify any natural site drainage patterns and determine how they can be maintained. Steeper sites usually generate more stormwater runoff.

Vegetation

Your site may have vegetation or trees you need to remove, or you may be able to incorporate existing vegetation in your design plans:

• Identify vegetation that can be incorporated into open space, used for wind protection or used as part of the site drainage system. Make it a priority to retain native vegetation where possible.
• Understand which trees might be protected and cannot be removed, and how this might affect the siting of your home. Also remember that trees take a long time to grow, so it is a good idea to retain them rather than starting again, if possible.
• Identify rare or endangered plant and animal species associated with the site. Your local field naturalist society will be able to help.

Resilience to the impacts of climate change

During the lifespan of your home, the climate is projected to change. Projections vary across Australia but, in general, include temperature rises and more frequent heatwaves, more frequent and more extreme droughts and floods, rising sea levels, more frequent high-intensity storms, more days of extreme fire danger and longer fire seasons. Refer to the Australian Government’s Climate change in Australia website.

Think about how climate change could affect your site over time, and consider strategies to help mitigate the risks.

• Ensure your house design is appropriate for your climate, taking into account projections for climate change in your area (generally, this means warmer and more extreme weather conditions). Refer to Passive cooling for more information.
• In bushfire-prone areas, check the risk level that applies to your block (for example, the bushfire attack level (BAL)). Bushfire risk can affect the type of construction materials allowable, which may, in turn, influence the cost of building or renovating.
• Build well above historic flood levels.
• Use construction materials that are resistant to fire, and impact (for example, hail).
• Use cyclone-resistant construction systems in areas of cyclone risk.
• Maximise capacity to capture and store water during periods of heavy rainfall with use of rainwater tanks, stormwater management, and landscape design.
• Consider onsite wastewater treatment and reuse if there is risk of insufficient rain.
• Choose garden plants, for example native plants, that can survive longer periods of drought.

A challenging site can set constraints on the design of your home. A number of strategies and techniques are available to address the design challenges of constrained sites and achieve sustainable outcomes. Getting advice from an experienced designer or builder can help you to achieve a comfortable, energy-efficient home, even on a difficult site.

It may be preferable not to build on a challenging site because of environmental impacts and additional costs. On the other hand, it is often possible to achieve good passive design and innovative solutions on challenging sites and they can be exciting places for creating a sustainable home.

Space

Efficient use of your block will allow you to get the best out of your home, reduce operational energy costs, and create benefits for your neighbours and the community. The size and shape of the block need to match your building design.

A ‘tight site’ has little flexibility in the fit. The shape of the block and the building schedule determines design responses and the practicality of different construction techniques. Specific design solutions may be needed to overcome issues of difficult orientation, air circulation and access. For more information refer to the Fremantle case study below.

Small blocks

Small sites are generally more constraining than large sites. You may also be dealing with restrictive ‘setbacks’, which are the clearances between the site boundary and building walls required by planning rules. Setbacks constrain the height and location of walls above ground level and will affect building volume and spatial configuration. They may also affect the size and orientation of windows where overlooking neighbours may be a problem. Setback requirements may exacerbate the limitations of certain sites and prevent construction in those areas.

Reduce the ratio of the building’s ground floor area to site area (building footprint) and use effective planning that eliminates waste space and optimises the footprint to increase the area available for landscaping. Increasing the number of storeys releases more site area, and allows optimisation of orientation, air circulation and access. Balance the building footprint with other impacts such as building height.

Building to the boundary (also known as zero lot line) maximises the amount of usable outdoor space. Wasted space in the form of a narrow side passage can be traded for greater space on the other side of the house. This is particularly beneficial if the house is built on the south boundary as it increases the amount of open space with a northerly aspect. For more information refer to Streetscape.

Poor orientation

The various strategies for dealing with poor orientation or solar aspect, particularly for existing homes, include adding solar reflectors to bounce light back into south-facing windows or effective adjustable shading, and using clerestory windows or advanced glazing systems. A building simulation or rating tool can help you to investigate options and their effectiveness.

Dense urban environments can provide the most constrained and challenging sites of all. It may be almost impossible to guarantee northerly solar access. In such locations, good designs can still achieve effective passive solar performance. It is possible, for instance, to use solar gain from non-northerly aspects to bring light and warmth into a house provided shading and ventilation is designed to complement the configuration.

Overshadowing by trees, natural features, or built structures can also affect the performance of onsite renewable energy systems. Remember to account for changes in the path of the sun over the year (see Orientation in the Passive design section).

Case study: Howard Street, Fremantle, WA

The brief was to design a passive solar, energy-efficient home on a tight, urban infill block. The long narrow block with an 8m frontage was orientated 45° west of north on the street and garage access was possible only at the front. Solar access was compromised by an existing 2-storey neighbouring building and the block was bordered by high parapet walls on both sides.

To overcome these obstacles, the front living room wall of the home was angled to face directly north with the ceiling of the room raked and tapered up to a window set in the gable to increase solar access. Air volume was minimised and thermal mass introduced on the floor and vertical internal walls. This ceiling and window configuration effectively almost doubles solar heat gain, which can then be stored in the vertical thermal mass. Two internal courtyards allow further solar gain and, combined with carefully selected shading for summer protection, also assist with airflow in summer to naturally cool the home.

Nationwide House Energy Rating Scheme (NatHERS) software, AccuRate, suggested a combination of advanced glazing and carefully designed shading be used on the windows facing the street, increasing useful floor area and reducing overall building complexity and cost. Low-e (low thermal emissivity) and double glazing are net collectors of winter solar energy, and north-east and north-west windows can be shaded by, for example, wing walls or adjustable awnings.

Source: Solar Dwellings – Energy Efficiency Homes

Slope

A site that is considered steep generally has a gradient more than 30°. The slope affects the type of home that can be built: flat house types (slab-on-ground) are good for flat sites; hillside houses (such as pole-framed houses) match steep sloping sites.

Steep sites require careful consideration of the contours for an appropriate design response. The slope may also be irregular with some parts steeper than others, and the fall may lie diagonally across the site. Strategies often used on steep sites include:

• balance cut and fill
• avoid retaining walls higher than 1m
• build along contours
• build into the slope to create an earth-sheltered home.

The slope also affects; the types of materials that can be used economically, solar access, wind exposure, and physical access to the building for vehicles, pedestrians and people with disability. On sloping sites, steep roads or large volumes of cut and fill may be the only solutions. Wheelchair access requires a ramp with a maximum incline of 1 in 14 (Australian Standard 1428.1-2009 Design for access and mobility – General requirements for access – New building work), which may need to be excessively long. A lift or similar device may be a cost-effective option in these situations.

Ground conditions

Ground conditions influence the type of foundations and disturbances to the site. Different soil conditions such as rock, sand, clay, or wetlands, place different constraints on design requirements.

Because of their inherent instability, the most challenging and difficult ground conditions are clay and wetlands. Rock presents the most stable ground condition but can be expensive and potentially damaging to the environment, to excavate.

Stormwater runoff

Steeply sloping sites increase stormwater runoff above and below the surface, from surrounding land and the site itself. Both site slope and hydrological ground conditions can constrain the building process and form.

Strategies for environmentally responsive design include:

• directing stormwater runoff to appropriate destinations — and using it effectively where possible
• collecting and using runoff for landscaping
• minimising interference with subsurface hydrology.

Early identification of existing artificial and environmental features is crucial. Artificial structures on or below ground level are best identified early in the site selection and analysis stage. Artificial structures can affect waste, pollution, solar access, wind exposure, bushfire risk and services, whether subsurface or overhead. The costs of mitigating existing conditions can create an unintended design challenge, so early identification is critical for effective site planning and later construction work.

Photo: Kathie Stove

Your home can change the nature of a site. Minimise the impact of your home on the natural environment by considering its effect on local flora and fauna; water, soil and air quality; and natural and cultural features. This need not add cost but simply requires forethought and careful choice of site.

Well-sited housing should:

• retain habitat so that local flora and fauna flourish
• protect waterways from pollution including stormwater runoff
• reduce the threat of bushfire to the home
• maintain or improve soil and air quality
• protect any valuable natural features such as vistas and ecosystems
• preserve existing culturally significant streetscapes and buildings.

Conserving habitat

If your chosen site already has good environmental values, retain existing native plants and fauna habitat where possible. Surrounding vegetation can help to keep your home cooler and mitigate urban heat island effects. Extensive vegetation removal can result in soil erosion and a reduction in soil quality.

Maintaining and enhancing existing habitats is a central issue on sites with high ecological value. Make an inventory of existing species and examine the impacts of site planning on species distribution and the viability of habitats. Establishing areas for habitat conservation becomes a central strategy; reduce noise and light pollution impacts of the home on these areas (see Landscaping and garden design in the Live and adapt section).

On sites with high ecological values, consider:

• establishing a habitat conservation area
• monitoring impacts of construction
• monitoring and adjusting activities that may disturb the habitat.

Flora and fauna impact studies are required by many local councils for larger developments. It is an environmentally smart choice to conduct one at a reduced scale for smaller projects, especially in areas with high natural heritage values or threatened species and ecosystems.

Design: Quentin Irvine, Inquire Invent Pty. Ltd. Photo: © Nic Granleese

Restoring and increasing ecological value

Urban development often removes existing flora and fauna, and inner-city sites rarely contain even remnant vegetation. Measures to restore or enhance ecological value are then needed. Reintroducing the local gene pool of the soil is imperative. If the soil from the site’s clearance has been stored, it can be reintroduced across the site. Subsurface and surface hydrology must be considered to re-establish catchments and enhance water flow across the site. On some sites, wildlife pathways can be created to allow animal movement across blocks, and plant food sources can be introduced for both humans and native animals.

If little ecological value remains or the pre-existing ecology has been destroyed, increasing the ecological value of the site as part of the landscaping plan is a good strategy, particularly on inner-urban sites. Strategies that increase biodiversity range from restoration of native species to the establishment of permaculture gardens (see Landscaping and garden design in the Live and adapt section).

• Australian Government Department of Housing and Regional Development (1995). AMCORD: a national resource document for residential development, Department of Housing and Regional Development, Canberra.
• Australian Institute of Architects (2008). Sustainability policy. [PDF] 
• Baggs D, Baggs J & Baggs S (2009). Australian earth-covered and green roof building, 3rd edn, Interactive Publications, Wynnum, Queensland.
• Climate change in Australia.
• Hollo N (2011). Warm house cool house, 2nd edn, Choice Books, New South Publishing, Sydney.
• Hyde R (2000). Climate responsive design: a study of buildings in moderate and hot humid climates, E & FN Spon, London.
• Hyde R, Watson S, Cheshire W & Thompson M (eds) (2007). The environmental brief: pathways for green design, Taylor & Francis, Abingdon, United Kingdom.
• King S & SOLARCH (1996). Site planning in Australia: strategies for energy efficient residential planning, National Energy Efficiency Program, Department of Primary Industries and Energy, Canberra.
• Oke TR (1997). Urban environments. In: Bailey WG, Oke TR & Rouse WR (eds), Surface climates of Canada, McGill-Queen’s University Press, 303–327.
• Your Home, Free home designs. 

Learn more

• Read Preliminary research to ensure you know what you are looking for when you design and build a home
• Refer to Designing a home to see how to get your ideas into a workable form
• Go to Insulation for more ideas on how to slow heat transfer through your home

Authors

Original authors: Chris Reardon, Richard Hyde, Catherine Watts

Contributing author: Caitlin McGee

Updated: Paul Downton 2013, Laura Wynne 2020