Using Recycled Building Materials in Construction
Deconstruction rather than demolition has been a driving trend across the globe as issues of sustainability and recycling assimilate into the construction industry.
The European Union’s 2008 Waste Framework Directive called for a minimum of 70% (by weight) of non-hazardous construction and demolition waste to be prepared for re-use or recycling by this year.
Barriers to recycling include concerns about the quality of the recycled products, their safety and the cost and time spent on sorting and preparing them.
Back home, our recycling problem increased in 2018 when China stopped importing waste plastics. This year, an Australian collaboration, including building panel manufacturer Bondor, received a $2.7 million Commonwealth grant to transform plastic waste into lightweight prefabricated building products.
Let's take a look at two recycled building materials in Australia - waste plastic being turned into building products and waste timber being re-purposed.
Is plastic the new timber?
From park benches and rail sleepers to fences and jetties, recycled plastic is replacing timber for many outdoor construction applications. Most plastic timber is made from high-density polyethylene (HDPE), polypropylene (PP), polystyrene (PS) and polyvinyl chloride (PVC).
In the past, recycled plastic products looked… well, like they were made of plastic! Now, sophisticated moulding, colouring and texturing produce products that look good, are easy to use and are virtually weatherproof.
To create a more pleasing look, plastic can be combined with wood fibres – wood plastic composite (WPC) products are commonly made from recycled HDPE. Used to make milk bottles, toys and plastic bags, HDPE is combined with wood fibres under heat and pressure, and surface embossed for a grained appearance. WPC products are popular for pool decking, thanks to their textured surface and water resistance.
Plastic recycling in Australia
According to the annual Australian Plastics Recycling Survey, Australians used 3.4 million tonnes of plastics in 2017-18. From that, 320,000 tonnes were recycled – roughly 9.4%. The rest is sent to landfill.
To reduce the 3.4 million tonnes of plastic we use each year, we need to find more constructive uses for recycled plastic products. After all, Sustainability Victoria claims producing plastic from recycled materials saves approximately 88% of the energy needed to make it from scratch.
The number of sophisticated, durable recycled plastic timber products entering the market is making a big contribution to our plastic problem and reinvigorating the industry.
Recycling used timber
Another recycled construction material is timber that’s already been used for construction. This could be old railway sleepers, girders, telephone poles, cladding or hardwood floors.
In order to standardise these recycled products, the Interim Industry Standard for Recycled Timber offers guidelines for visually graded decorative timber. Published by Forest and Wood Products Australia, the interim standard covers small end-section timbers less than 0.012 m2 from timber sawn from larger sections.
Timber is categorised into three Recycled Feature Grades, with RFG1 being the least blemished. The interim standard dictates the number and size of knots, checking, gum pockets, holes and other blemishes allowed in each grade. However, a resourceful carpenter will see the possibilities of all three grades, matching appearance to application.
Plastic and timber are commonly used recycled building materials in construction, but there are many others, including steel. And although there are also experimental materials – roofing made from used nappies, walls made from mushrooms – these are not (yet!) serious contenders.
Industry members who keep an open mind on emerging technologies may have an edge on those who remain tied to old ways of working. Just as carpenters a century ago would have laughed at the idea of sawing plastic, who knows what we will be cutting into in the decades ahead?