Transite is a Johns-Manville trademark for asbestos-cement building panels. If your home has gray cement-like siding or corrugated roofing panels and was built before 1986, the material may contain up to 50% asbestos by weight. That number is not a worst-case scenario. It was the design specification.
How to identify cement siding (transite)
Cement siding has a hard, brittle feel. It cannot be bent or flexed. Under pressure it snaps, unlike modern vinyl or wood siding. Transite was manufactured in light gray; painted examples may be any exterior color, but stripping to bare surface reveals gray or off-white cement.
Two primary profiles exist: corrugated panels (rounded ribs, approximately 4.2 inches center-to-center) and flat or textured shingles that resemble wood grain. Both formats are suspect on pre-1986 construction. Many residential applications used shingles approximately 12 by 24 inches with a fish-scale or straight lower edge.
If a piece is already broken, examine the cross-section. Asbestos-cement shows a fibrous, cement-like internal structure rather than the clean cut you would see in PVC or modern engineered wood. Cape Cods, ranch homes, bungalows, and split-levels from 1940 to 1975 are the most common residential candidates. Transite shingles and panels rarely carry visible manufacturer markings on the exterior face.
Key visual cues:
- Rigid, brittle siding shingles roughly 12x24 inches with a wavy or straight butt edge.
- Surface has a chalky, matte texture even when painted.
- Shingles feel heavier than modern fiber cement (though visually similar).
- Often drilled with two nail holes near the top edge.
- Common on homes built 1940 through 1980, especially Cape Cod and post-war ranch styles.
Risk by home build year
| Era | Risk | Reason |
|---|---|---|
| Before 1985 | Do Not Disturb | Standard residential and commercial exterior cladding. Contains 10 to 30 percent chrysotile asbestos. |
| 1985 to 1995 | Test Recommended | Transition to cellulose fiber cement. Some asbestos product still shipped. |
| After 1995 | Low Risk | Modern fiber cement (HardiePlank, etc.) is cellulose-based. |
Safety
Do not power-wash, saw, sand, drill, or break asbestos-cement siding. Repainting intact siding is generally permitted; any abrasive prep is not. Replacement requires trained abatement when the shingles are disturbed.
Source: EPA: Asbestos NESHAP. OSHA 29 CFR 1926.1101 for exterior renovation.
What to do next
- 1
Test before any drilling, cutting, or replacement work
Collect a bulk sample chip or fragment from a section that is already broken. Do not break intact siding to sample it. Western Analytical accepts cement-based composite materials. EMSL accepts all building material types. If no piece is broken and accessible, hire a certified inspector.
- 2
Contain any existing damage
If panels are already cracking or fragmenting, the immediate priority is preventing further disturbance. Do not pressure wash cement siding. Pressure washing is a common disturbance event that can crack aged transite and release fibers across an exterior surface area.
- 3
Licensed abatement for any removal
Per EPA NESHAP, asbestos-cement material removed during renovation or demolition is regulated waste. It cannot be placed in standard construction dumpsters. National cost range: $3–$15 per sq ft for siding removal. Whole-home siding abatement: $5,000–$20,000 or more.
Regulatory authority
The U.S. EPA's NESHAP regulations govern transite siding removal, specifying that it is regulated ACM that requires licensed handling and cannot be disposed of as standard construction debris (EPA, "How EPA's Asbestos Regulations Apply to Transite Siding," epa.gov). OSHA's construction standard (29 CFR 1926.1101) establishes that any cutting, drilling, or removal of asbestos-cement products requires OSHA-compliant work practices and respiratory protection (OSHA, osha.gov). The Bay Area Air Quality Management District has published a practical enforcement advisory on transite disturbance during renovation (BAAQMD, "Asbestos Cement (Transite) Siding and Roofing Advisory," baaqmd.gov).