Building materials

When you contemplate constructing a new home or extension, one of the first decisions you must make is what materials to use.

There are many factors that will help determine the type of construction you choose, and it might be worth thinking outside the range of conventional materials to achieve what you want. In Australia the most common materials used in residential construction are double brick, brick veneer, concrete block and lightweight construction.

Other less common materials are tilt-up and pre-cast concrete, mud brick and rammed earth. Each has its own benefits and drawbacks, which need to be assessed before you make a decision.

For many home builders this decision is taken away when they decide to engage a project home company. What makes most project homes cheaper is standardisation and any variation from the standard materials, finishes and fixtures will be reflected in the construction costs.

Brick veneer is the staple of this type of construction. Brick veneer is a double skin wall construction consisting of an exterior skin of brickwork and an interior layer of either steel or timber wall framing with panel cladding, most commonly plasterboard.

With sufficient wall insulation installed there is nothing wrong with this type of construction and it can be made to perform as well, both thermally and acoustically, as cavity brick walls.

For many the ideal construction is still cavity brick. There is a strong perception that this is the most solid and reliable form of construction and it remains a popular option.

More expensive than other options, it has the benefits of providing strong resilient internal and external walls which are much more impact resistant than lightweight alternatives. Concrete block has emerged as a strong contender in the residential construction market in recent years.

There is a range of grades available, from high quality face block which needs no further finishing, to the cheapest grades which must generally be rendered to provide an attractive finish. Concrete block can also be combined with a lightweight internal skin to create concrete block veneer construction.

In a climate like Sydney’s it always surprises me how resistant people are to experimenting with lightweight construction. Ironically, the cooler states, such as Victoria and South Australia, seem far more open to this than New South Wales.

Lightweight construction consists of steel or timber framing with sheet material cladding, both exterior and interior, including, amongst others, sheet metal products, weatherboards, fibre cement sheet, plywood or plasterboard.

There are historical examples of lightweight housing in Sydney, such as the many weatherboard homes in Balmain, but they still remain a rarity. When provided with adequate insulation, lightweight walls can perform as well as masonry in terms of thermal insulation, but are still somewhat inferior in terms of acoustic insulation.

Materials still deemed to be alternative are ones such as mud brick and rammed earth. Despite the great environmental advantages of these materials it’s hard to destroy their image as grungy hippy materials, but done well they can look fantastic, and perform well thermally too.

Rammed earth, virtually unknown in NSW, is simply a mixture of sand and available soil packed into formwork and rammed mechanically until it reaches the density and hardness close to that of sandstone. Constructed in layers, the result is a very earthy, warm and textural wall that provides a beautifully different aesthetic to conventional materials.

With the availability and simplicity of conventional construction materials, alternative materials might not seem worth the effort but, if you’re aiming for something a little different from your neighbours, it’s definitely a good place to start.