Asbestos cement first came into use as an exterior cladding after 1907, when Austrian engineer Ludwid Hatschek came up with a way to shape the material into sheets, allowing it to be manufactured as siding and shingles. By the 1920s, the National Board of Fire Underwriters recommended that asbestos cement replace wood as siding and roofing material because of its superior fire-resistant properties. This recommendation from a nationally known insurance board contributed to a boost in sales and, by the 1940s, hundreds of thousands of homes in the U.S. had been constructed using asbestos cement siding.
During the late 1960s and early ‘70s, however, the news media began to report on the health hazards associated with asbestos. As reports increased, concern grew, so the federal government took action and, in 1973, the EPA banned the use of asbestos in the manufacture of building products.
Health Risks Associated with Asbestos Cement
Asbestos fibers are a proven health hazard if inhaled. Asbestos dust is a known cause of a type of lung cancer called asbestosis. Mesothelioma, another deadly form of cancer that attacks internal organs, can also be caused by exposure to asbestos. However, asbestos cement siding that has been properly installed and is not in a state of decay presents no health risks as long as it remains undisturbed. This is because the cement binds the asbestos fibers and prevents their release into the air, under normal use and maintenance.
The EPA deems asbestos to be hazardous when it is in a friable state, meaning that it can be crumbled, crushed or pulverized by hand pressure. Crushed asbestos in a powdery form can allow its particles to become airborne and inhaled, causing potential health problems. Asbestos cement products that are not in a friable state are not considered hazardous. The only potential danger is when the cement is disturbed in a way that causes the asbestos fibers to become airborne.
If mechanical activities performed on the siding, such as chipping, sawing, grinding or sanding, allow particles to become airborne, then the cement is considered in a friable state and, consequently, hazardous. Deterioration can also lead to particles becoming airborne and potentially dangerous.
Damage and deterioration can lead to structural and health issues, so proper maintenance of asbestos cement building materials is a primary concern. Keeping the siding clean and performing any minor repairs as soon as they become necessary are both important.
Asbestos cement siding is fairly brittle and has little resistance to cracking, chipping and damage from impact, which can cause asbestos particles to become airborne. Damage to the siding can also lead to other damage related to moisture intrusion. Damaged areas that cannot be fixed can be replaced with non-asbestos fiber cement by a professional. Specific fiber cement materials have been manufactured for repairs that are intended to mimic the look of asbestos cement siding.
Landscaping features, such as a row of shrubs, can be incorporated around the home to help protect the siding from impact damage.
Here are some common problems associated with asbestos cement siding that inspectors are likely to encounter: