For many years, fiber-cement roofing materials were manufactured with an asbestos content in the 5% to 35% range. The only way to determine actual asbestos content is through laboratory testing. The best term for identifying these shingles is "fiber-cement with a high likelihood of some percentage of asbestos content".
You may hear older materials referred to as Transite, which is a Johns-Manville trade name originating in the late 1920s, but roofing products containing asbestos were also manufactured by CertainTeed, GAF, and others. Chrysotile is a type of asbestos commonly used in roofing products. Once a roofing material is positively identified as containing asbestos, your client will probably be required by disclosure laws to make potential buyers aware of its presence.
Qualified roofing contractors should be aware of the dangers connected with its removal when the roof must be replaced. Fiber-cement shingles manufactured after asbestos was prohibited contained cellulose materials as substitutes and due to non-compatible expansion and contraction rates between cement and cellulose, these roofing materials deteriorated relatively quickly.
Modern Transite roofing materials are manufactured using crystalline silica which has been classified by the International Agency for Research on Cancer (IARC) as being carcinogenic to humans. Fiber-cement materials containing asbestos have been used in the production of shingles, corrugated roofing, underlayment, roof sheathing, and many other products.
Asbestos becomes a health hazard when it is friable, meaning in a condition in which fibers become airborne and may be inhaled. As roof products age and deteriorate, they may release fibers into the air. Fiber-cement roofing materials are often- but not always- grey.
Fiber-cement roofing included various percentages of asbestos until the early 1980s. For a while, asbestos was banned in many products and manufacturers tried substituting other products, including cellulose, which didn't work out well.
Tiles with 50-year warranties failed quickly and lawsuits reduced the number of manufacturers producing fiber-cement roofing.
In reports, when encountering old fiber-cement roofing, inspectors SHOULD NOT refer to it as asbestos roofing. The same is true for siding. Both products had varying amounts of asbestos, depending on manufacturer.
Do not walk fiber-cement roofing.
What it is
-
Fibers reinforce the cement matrix to improve toughness and reduce cracking compared with plain cement products.
-
Products are manufactured as individual shingles/shakes, flat “slate” tiles, or corrugated sheets for agricultural and light‑commercial roofs.
Key advantages
-
Durability: Resistant to rot, insects, and UV, with good performance in heavy rain, wind, and hail when properly installed.
-
Fire resistance: Typically non‑combustible and often rated at Euro Class A1 or similar, which is useful in WUI or high‑fire‑risk areas.
-
Dimensional stability: Does not warp like wood and maintains relatively low movement with temperature changes.
-
Low biological risk: Resists mold and fungus compared with organic shingles when kept reasonably dry and ventilated.
-
Aesthetics: Can mimic wood shakes, slate, or flat tiles in various factory colors and textures.
Main drawbacks
-
Brittleness and impact issues: Shakes and slates can crack or spall under hail, foot traffic, or repeated wind‑driven debris; some products weather faster than expected.
-
Moisture absorption: Boards can take on water; in freeze–thaw climates this promotes micro‑cracking and accelerated surface degradation if detailing or coatings are poor.
-
Weight: Heavier than asphalt shingles and many synthetics, so existing framing sometimes needs verification or reinforcement.
-
Maintenance: Shake‑style products may need periodic repainting (on the order of every 10–15 years) and more frequent inspections to deal with cracked or loose pieces.
-
Health and cutting: Sawing releases respirable crystalline silica, so installers must use dust control, respirators, and appropriate cutting methods.
Typical service life and applications
-
Service life is often marketed in the 20–50‑year range depending on product type, climate, and maintenance; some corrugated panels claim 50‑year expectancy with manufacturer guarantees around 10 years.
-
Used on residential pitched roofs (shake/slate look), agricultural and industrial buildings (corrugated sheets), and where a non‑combustible, rot‑resistant covering is needed.
Quick comparison to common options
| Aspect | Fiber‑cement roofing | Asphalt shingles | Concrete/clay tile | Synthetic composite shakes/tiles |
|---|---|---|---|---|
| Weight | Moderate–high, lighter than concrete but heavier than asphalt. | Low. Widely accepted on standard framing. | High; often requires stronger framing. | Low–moderate; often lighter than fiber‑cement. |
| Fire resistance | Non‑combustible, high fire ratings. | Varies; many are fire‑rated but still combustible base. | Non‑combustible. | Varies by product; many are high‑fire‑rated. |
| Moisture/rot | Rot‑proof but can absorb water and suffer freeze–thaw damage. | Organic base can age and curl; no freeze–thaw spalling. | Very good; tiles are not moisture‑sensitive. | Very good; low moisture absorption. |
| Hail/impact | Can crack or spall; brittle under point loads. | Performance depends on impact rating. | Tiles can also crack under heavy impact. | Often engineered for higher impact resistance. |
| Maintenance | Periodic inspection, repainting for shakes, replacement of cracked units. | Relatively low; full replacement at end of life. | Low on tiles themselves, but flashing and underlayment still critical. | Generally low; focus on fasteners and flashings. |
| Aesthetics | Good wood/slate simulation, many colors. | Limited dimensional relief; many color options. | Traditional “tile” look; strong visual weight. | Can closely mimic wood, slate, or tile. |