Principal author of the Hemp Masonry listing at www.yourhome.gov.au Dick Clarke from Envirotecture produced this fantastic entry level guide for the Australian government. See more at yourhome.gov.au | Hemp Masonry
Key points of building with Hempcrete
- Hemp masonry is made of the woody part of the stem of a hemp plant, combined with lime binder, water, and sometimes sand.
- Hemp masonry has good thermal performance, and is a breathable material that reduces condensation and improves internal air quality.
- It has low environmental impact; it is a renewable material, and hemp crops generally have low water and fertiliser needs. They also absorb carbon during the growing process.
- To construct a hemp masonry wall, wet hemp mix is placed directly into a timber frame. Care needs to be taken with the detailed design and construction around doors and windows to avoid cracking.
- The hemp mix usually dries to touch in about 7 days, but the curing process takes 3 months.
- External walls must be rendered. Internal walls can be left un-rendered and should be finished with a vapour-permeable semi-penetrating clear sealer.
- A half-strength hemp-lime mix, without sand, can be used to provide insulation on top of a suitable ceiling or in a subfloor.
Exterior of a house constructed using hempcrete
Photo: Amber Creative
Understanding Hemp Masonry
Hemp masonry (also known as hempcrete, or hemp-lime composite) is a composite material made of hemp hurd – the inner woody part of the industrial hemp plant’s stem – lime binder and water. Sand can be added to minimise the use of lime binder and to provide a little thermal mass.
Although hemp masonry has recently become popular in the construction of homes with low environmental impact and good thermal performance, it has been used as a building material for at least 300 years. Hemp has also been used for fabric, ropes, and food for thousands of years. The industrial hemp plant used for these applications contains virtually none of the drug THC that is associated with marijuana.
As a building material, hemp masonry offers ecological and economic benefits from beginning to end: for the farmer, the processor, the builder, and the building occupant. Hemp masonry provides very good insulation at the same time as being highly vapour permeable, which makes for very comfortable buildings with good indoor air quality.
Keep reading at yourhome.gov.au | Hemp Masonry
