Fiber Cement Siding/Cladding

Fiber cement siding and cladding are portland-cement based panels that are reinforced with cellulose for improved durability. They are commonly manufactured via the Hatscheck process where slurries containing cement and fibers are formed to a given thickness, and then compressed together and cured. The slurries also contain sand, fillers, and additional additives, but the additional additives are not well disclosed. Fiber cement panels and shakes are typically marketed as asbestos-free and often used in residential applications to replace asbestos siding. Products can come with factory applied finishes or waterproofing treatments. Some products are sold with a factory-applied primer and are painted on site. Others are supplied with a factory-applied paint and primer.  This common product describes a fiber cement panel with a factory-applied latex primer. Waterproofing treatments and finish paints can add additional hazards not covered by this Common Product. 

The addition of water to portland cement causes it to cure, or harden, as the water becomes part of its chemical structure. While fiber cement siding and cladding is cured prior to arriving at the construction site, manufacturer documentation generally reports the content of cement cladding and siding as the chemical structure would appear prior to curing. Because the composition of cured cementitious products is highly variable and involves several chemical reactions, this Common Product breaks out the content of Portland cement and concrete prior to curing. The typical reaction products of portland cement and water are included in the All Contents tab, but the weight percent is not calculated.