Asbestos in Exterior Building Materials

By Stan G. in Construction

Before the 1980s, exterior building materials containing asbestos were common in the construction industry. Because of the fire- and heat-resistant properties, asbestos was the perfect solution as a fire-retardant insulator in panels, roofing, and structural applications. Therefore, the buildings built between 1920 and 1980 potentially have in some form asbestos exterior materials.

Asbestos is a health risk factor when its fibers become airborne. If inhaled or ingested, it can cause severe diseases that can develop decades after exposure. However, asbestos that isn't airborne is not inherently dangerous. It represents a risk only when disturbed through drilling, cutting, sawing, or breaking. For safety reasons, if there's no information available on whether a building material contains asbestos or not, it should be treated carefully.

Building exteriors that could contain asbestos fibers:

  • cement siding panels
  • stucco
  • cement soffits
  • cement roof panels
  • roofing felt and mastic
  • thermal spray
  • brick mortar
  • loose fill insulation in exterior walls (vermiculite)
  • fireproofing spray on structural members
  • external angle moldings
  • external wall sheeting
  • exterior paint

Asbestos in the Roofing Shingles and the Under-Lay

Cementitious products contained asbestos fibers as a strengthening material. Generally, asbestos-cement materials harden with age, and asbestos loses its impact power over time due to atmospheric carbonation. Even so, asbestos cement roofing can become brittle and may shed asbestos in roof runoff and debris. Cracked surfaces on shingles are common due to exposure to natural elements, but there are no asbestos-releasing damages. Mechanical damages from ice, impact, or steps of careless contractors and installers represent a real risk of releasing asbestos into the air.

Besides the roof tiles, there's the asphalt tar paper that contains asbestos. It is used as the underlay that keeps the plywood durable and dry. The tar paper will break down over the years due to exposure to extreme heat, stick to the plywood and peel off when removed. Asbestos can also be found in the asphalt shingles, especially if the home was built before the 1980s. Corrugated cement panels were used in building smaller roofs such as garages, garden sheds, and smaller adjacent buildings. These panels can break apart when removed, sending asbestos fibers into the air.

Asbestos in the Window Putty

Asbestos was a filler in window putty, adding strength and fire resistance. When exposed to heat, some types of asbestos-containing putty swell, increasing in volume but decreasing in density. As the putty weathers, it starts to crack or crumble, and asbestos can become friable.

Asbestos fibers can become airborne when work is done on the windows. It is best to avoid digging out pieces or removing dust or bits of putty. Replacing the glass panes and frame should be postponed until tests for asbestos are done. Using high-speed power tools such as sanders, drills, or grinders on the frames would create dust that could likely send asbestos fibers into the air.

Asbestos in Stucco and Plaster Applications

Construction materials containing asbestos are the components of cement sidings, stucco sidings, and plaster applications. Asbestos was also a strengthener in some of the older plaster walls, acoustic insulation, or fireproofing applications - materials that may look like standard sprayed-on plaster applied to surfaces for the finish. It could be present in homes as a decorative coat on walls, textured ceilings, drywall, and exterior stucco finishes. Disturbing these materials during renovations and repairs can release harmful levels of asbestos fibers.

Find Out If Your House Has Asbestos by Checking the Materials Used When Built

Asbestos in the stucco siding and plaster is so difficult to spot that most people overlook it. Locating asbestos is complicated as it has no smell and doesn't have a specific feature visible to the naked eye. One of the quickest ways to identify asbestos in construction materials is to check their composition. But in older buildings, finding what was used in the construction process is next to impossible, as there is no comprehensive list of what brands and materials could contain asbestos.

Here are some manufacturers that used asbestos in their products:

  • W.R. Grace - used asbestos plaster
  • Georgia-Pacific - used asbestos in acoustical and patching plaster
  • Synkoloid
  • Keene
  • National Gypsum - the 'Gold Bond' brand plaster had asbestos in it
  • United States Gypsum - produced asbestos plaster

What to Do If There Is Asbestos in Your Home

First and foremost, don't panic if you believe asbestos may be in your home. Generally, the best thing is not to disturb the asbestos material. Construction materials in good condition will not release asbestos fibers; therefore, inhaling them is no danger.

If you suspect a material containing asbestos, check it regularly. Look for signs such as tears, abrasions, or water damage. Damaged material may release asbestos fibers if often disturbed by handling, hitting, rubbing, or exposed to extreme vibration or airflow. If there is slightly damaged material, limit access to the area and do not touch or disturb it. Leave the removal and repair to people trained and qualified in handling asbestos. Should you choose to handle the asbestos products in your home, we recommend reading our page to guide you on safely removing asbestos-containing building materials from your house.

Why Should I Test Products in My Home for Asbestos?

It is often impossible to tell whether asbestos is embedded in a material, as the fibers are too small to be observed with the naked eye. Exposure to asbestos is responsible for serious respiratory conditions, so thorough testing is required to ensure your home is asbestos-free.