Fibre cement is used primarily to make siding and cladding panels for commercial buildings and private homes. This material is composed of sand, cement and cellulose, and gives the look of wood without the maintenance difficulties. However, the production process can be energy-intensive. Learning about fibre cement manufacture can help homeowners make the right choice when choosing new siding for their homes.
According to BGC, fibre cement is made from four major raw ingredients: silica, usually from sand; water; cellulose from paper; and cement. The fibre helps reinforce the cement panel, preventing cracking or breaking under pressure. Older cement panels often used asbestos fibres instead of cellulose, but these pose a health hazard when broken. Cellulose in fibre cement panels does not pose the same danger, though workers should wear respirators when cutting this material.
To produce fibre cement, manufacturers combine the raw ingredients into a slurry. This slurry is filtered to remove large pieces, then fed into a press roller, which creates a consistent layer of material between 4 and 15 millimetres thick. The pressed cement must then be allowed to rest for 24 hours before it can be autoclaved.
After the fibre cement panel has rested, it is then placed in an industrial autoclave, or steamer. The panel is steamed at 180 degrees Celsius for eight hours. At the end of this period, the steam is released into another autoclave or into a tank, taking with it most of the smell from processing. Some odours do remain, and may cause problems for people living near fibre cement factories. The panels are allowed to cool, and may be used as-is or painted before use.
Fibre cement panels may be painted at the factory, or after installation. However, factory-coloured panels are often more durable. According to ToolBase, some manufacturers offer paint warranties of up to 25 years on their fibre cement panels. Most panels are painted using an alkaline-resistant primer, to prevent paint degradation from contact with the alkaline cement. An acrylic topcoat is applied over this primer.
While fibre cement is a durable, low maintenance material, its manufacture does create some problems. Producing the cement involved in making these panels requires decarbonisation of limestone, an energy-intensive process. Fibre cement panels have a high embodied energy, and may be difficult to recycle. Nonetheless, their long product life makes them more environmentally friendly than many shorter-lived types of siding.
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