For centuries, building and home construction consisted of using materials native to the area. Walls contained a cob mixtures of clay, soil and grasses. Roofs were thatched with an array of bound grasses. As construction equipment and knowledge advanced, concrete, wood and metal became more widely used. Beginning in the 1990s, in an effort to reduce environmental waste and find renewable sources of materials, builders developed a renewed interest in implementing cellulose-based components in construction projects.
Historically, the most common options of cellulose-based products included hemp, jute, straw or wood. The complexity of the carbohydrate containing fibres offered a high degree of strength and excellent insulation though used at reasonably low densities. Modern processing techniques mean that fibres are typically converted for spraying into place or pre-casted into ready-made forms. Using these products requires a certain degree of pre-treatment as crop-based materials are not without drawbacks in a natural state.
Risks outlined by the National House Building Council include:
- Biological degradation-Moisture reduction is necessary to prevent mold formation. The addition of lime increases material pH and inhibits mold formation.
- Fire-Materials must undergo flame retardant treatment to reduce the risk of ignition and combustion.
- Pest infestation-Natural materials attract a number of pests that include animals and insects. Natural materials must be used in a timely fashion and not allowed to remain on-site for extended lengths of time in order to prevent infestation. Treatment with lime or covered with lime containing materials also makes crop products less desirable once installed into a building.
- Moisture-The likelihood of degradation or infestation might also occur the longer natural materials remain in an open environment and come in contact with various weather conditions. Materials must either be used quickly or safely sheltered until becoming a part of the structure.
- Structural degradation-The amount of weight that building materials undergo once installed must meet load-bearing standards. When used for insulation purposes, the grass-based products must also be manufactured in such a way as to eliminate the possibility of settling after installation.
Hemp and lime combinations, along with straw bale panels, have been successfully used as construction materials for dozens of structures throughout the UK. These structures have included a number of housing projects. Through the use of natural materials, contractors have completed more than 100 homes on Denmark Lane, Diss and in Norfolk. More recent examples include the Cheshire Oaks Marks & Spencer store located near Ellesmere Port. Future building endeavours using natural materials are estimated to create up to 500,000 cob and earth based buildings and around 40,000 structures having traditional thatched roofs.
Hemp remains an underrated building material. Due to misinformation many there is a lot of confusion on the differences between hemp and marijuana. Both origin from Cannabis Sativa, however industrial hemp includes minimalistic to no amounts of THC. Justice and law revolving around hemp is a cloudy and grey area; while the posession and trade of both industrial and cannabis seeds are legal, the cultivation and posession of marijuana is not. Growing industrial hemp in the UK is possible under strict regulations and the industry is slowly embracing the plant, however it’s a slow and eventful process.