Hemp construction in Australia
Among the companies building with hemp is Hemp Homes Australia, based in Margaret River, Western Australia. It focuses on passive solar, custom-designed hemp houses, with the first example having recently been completed, and five others in the pipeline. To secure a local hemp supply, Western Australia’s growers are calling for investment in a processing plant that would allow locally sourced hemp to be used, or better still, for a network of them dotted around the state. Colin Steddy, director of The Hemp Corporation, has plans to invest in getting one off the ground.
A couple of Australian ecovillages under construction will be using hemp. These are Shepherds Ground, near Maitland in the Hunter region, and Witchcliffe Ecovillage near Margaret River in Western Australia. So far, dozens of hemp houses have been built across the country.
Hempcrete is the name for the most commonly used type of hemp houses building material. Because a hemp-lime mixture is not dense enough to be load-bearing, hempcrete is commonly used in conjunction with post-and-beam construction, and is applied inside a formwork. Encasing the timber frame, it takes on the roles of cladding, insulation, and Gyprock. Another construction option involves hempcrete blocks, but due to the gaps these have an inferior thermal insulation compared to cast hempcrete. Hempcrete can also be used in the insulation of flooring, the under-floor area, and roofs.
If you are looking to build a new house from hemp, it is important to recognise that hempcrete construction is a mature technology that has been tested in Europe for the past 30 years. Roughly speaking, you can anticipate that hemp will be approximately the same cost as brick and other commonly used materials. For non-owner-builders, it is recommended to use a company that has previously built hemp houses, or is committed to attending trainings or workshops such as those held regularly by the Australian Hemp Masonry Company. This is particularly important because hemp materials behave differently from their conventional equivalents. Specifying hemp in the contract is one way to ensure that it is not substituted for something else that lies within a mainstream house builder’s comfort zone.