Asbestos Sheet Siding and Wallboard: Identifying It on Your Home
Flat asbestos cement sheets were used as exterior siding and interior wallboard in homes built before 1985. Learn how to identify them, what they look like, and what to do before any renovation work.
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Asbestos Sheet Siding and Wallboard: Identifying It on Your Home
Flat asbestos cement sheets were manufactured from the 1920s through the mid-1980s and used as both exterior siding panels and interior wallboard. If your home was built before 1985, there is a real chance these panels are somewhere on the structure. Left undisturbed, the material poses no immediate risk. The hazard comes when you cut, drill, sand, or break it.
What Asbestos Sheet Siding Looks Like
Asbestos cement sheet siding comes in flat, rigid panels. The most common sizes are 12 by 24 inches and 16 by 32 inches, though manufacturers produced other dimensions. The surface is typically smooth to lightly textured, with a grayish or off-white color. Decades of weathering often give old panels a chalky, faded appearance.
A few visual and physical cues:
- Thickness: Between 3/16 and 5/16 of an inch. Thinner than drywall but heavier than you would expect for the size.
- Weight: Noticeably dense. A single 12x24 panel weighs roughly 3 to 5 pounds.
- Brittleness: Asbestos cement is rigid. Old panels crack in clean, straight lines rather than bending or flexing.
- Fastener pattern: Typically nailed at regular intervals, often with visible nail heads near the top edge of each panel.
- Corner trim: Exterior corners frequently have a separate metal or asbestos cement corner piece.
Common brand names include Eternit, Colorbestos, and Flexboard. If a panel is loose or partially removed, check the back face for stamped or printed manufacturer marks.
Asbestos Flat Sheet Wallboard
Asbestos was also used in flat sheet form for interior applications: wall panels in utility rooms, basements, and garages; fire-resistant backing behind furnaces and wood stoves; and substrate under tile in bathrooms and kitchens built before 1980.
This material looks similar to exterior sheet siding but was often thinner and sometimes finished with paint or tile adhesive. In many homes, it served as a fire-resistant backer rather than a finished surface, so it may only become visible when you remove tile, paneling, or other finish layers.
If you are renovating a pre-1980 basement, pulling out an old wood stove surround, or retiling a bathroom in an older home, flat asbestos wallboard is a realistic possibility.
When These Products Were Made
Asbestos cement sheet products were manufactured in the United States primarily from the 1920s through the early 1980s, with peak production during the postwar building boom of the 1950s and 1960s.
The EPA began restricting asbestos use in stages, starting with spray-applied asbestos in 1973. Asbestos cement sheet products for construction were not formally addressed until later under the Toxic Substances Control Act. Some manufacturers phased out asbestos content through the late 1970s and early 1980s, while others continued until regulations required it.
A practical guideline: homes built before 1980 have a high probability of containing asbestos sheet materials if flat cement panels are present. Homes built between 1980 and 1986 fall in a transition window where some products were still asbestos-containing. After 1990, asbestos cement sheets were no longer produced for residential construction in North America.
How to Tell If Your Panels Contain Asbestos
Visual inspection alone cannot confirm asbestos. The only way to know for certain is laboratory testing. That said, visual and physical cues narrow the probability:
| Feature | Higher probability | Lower probability |
|---|---|---|
| Installation year | Before 1980 | After 1990 |
| Weight for size | Heavy, dense | Light or flexible |
| Texture | Flat, rigid, brittle | Flexible, vinyl-like |
| Color | Gray, off-white, chalky | Bright white, patterned vinyl |
| Visible branding | Eternit, Colorbestos | James Hardie, modern fiber cement |
If your panels match the higher-probability column, treat the material as potentially asbestos-containing until tested. The ATSDR recommends treating all suspect materials in older homes as asbestos-containing until laboratory analysis confirms otherwise.
Modern fiber cement products (such as James Hardie siding) do not contain asbestos. They were specifically developed as asbestos-free alternatives. If your siding was installed after 1990 using a named brand product, asbestos is not a concern.
The Risk: Intact vs. Disturbed
The EPA's guidance on asbestos in the home is consistent on this point: asbestos-containing materials in good condition and left undisturbed do not pose a health risk. Fibers become airborne only when the material is cut, sanded, drilled, or otherwise disturbed.
Sheet siding in good condition on the exterior of a home is not a priority concern. What triggers risk:
- Cutting or drilling panels during renovation
- Sanding weathered, chalky surfaces
- Removing panels during re-siding work
- Breaking panels that have cracked from impact or age
"Friable" asbestos describes material that can be crumbled by hand pressure. Intact asbestos cement sheets are non-friable. Weathered panels, however, can become more friable over time as the cement binder degrades, particularly on the outer surface layer. If panels are visibly deteriorating or crumbling at the edges, that changes the risk calculation.
What to Do Before Any Work
- Do not disturb the material. If panels are intact and you have no renovation planned, no action is immediately required.
- Test before any work that would contact the panels. A mail-in asbestos test kit costs $30 to $50 and returns results from an accredited lab within 5 to 7 business days. Collect a small sample using the kit instructions, seal it, and mail it in.
- If positive, hire a licensed abatement contractor. Removal of asbestos-containing exterior siding requires a licensed abatement contractor in most US states and Canadian provinces. Your state or provincial environmental agency maintains a list of licensed contractors. The EPA's asbestos resources page is a starting point.
- Do not attempt DIY removal. Siding removal generates significant dust and debris. Proper containment, PPE, and disposal protocols are required and are not a DIY project.
FAQ
Can I just paint over asbestos sheet siding instead of removing it?
Painting over intact asbestos cement siding is generally acceptable as a short-term measure and is sometimes called encapsulation. The EPA notes that encapsulation can reduce risk when material is in fair condition. It does not eliminate the underlying issue. Any future removal will still require abatement procedures. Check with your state environmental agency before proceeding, as requirements vary.
How much asbestos is in cement sheet siding?
Asbestos cement sheet products typically contain 10 to 20 percent asbestos by weight, primarily chrysotile (white asbestos). That is a higher concentration than some other building materials. The asbestos is bound within the cement matrix, which is why intact panels carry lower risk than friable materials like spray-on insulation.
Is fiber cement siding the same as asbestos cement siding?
No. Modern fiber cement products use cellulose fibers or wood pulp instead of asbestos. They were developed specifically as asbestos-free replacements after regulatory pressure in the 1980s. If your home was re-sided after 1990 using a named brand product, it almost certainly does not contain asbestos. Pre-1985 flat gray cement panels are a different category entirely.
Do I need a professional to collect the sample for testing?
No. You can collect a sample yourself using a mail-in test kit. Wear a P100 respirator and nitrile gloves, wet the material lightly first to reduce airborne fiber release, and follow the kit instructions exactly. Most accredited labs accept homeowner-collected samples alongside professionally collected ones.
What does asbestos sheet siding removal cost?
Costs vary by region, volume, and local disposal requirements. National averages tracked by Angi range from $20 to $65 per square foot for professional abatement, with whole-house siding projects commonly falling between $5,000 and $15,000. Get at least three quotes from licensed abatement contractors. Some state programs offer lower-cost options for owner-occupied homes.