The only way to know if siding is asbestos cement is a laboratory sample analyzed by polarized light microscopy, which costs $40 to $90 per piece and takes two to five days. Visual clues, a house built or resided between the late 1930s and the early 1970s, a rigid board that rings when tapped and chips with a chalky edge, tell you whether a test is worth ordering. Washington treats any material over 1 percent asbestos as regulated, and cement siding usually tests between 10 and 20 percent chrysotile.
What cement asbestos siding looks like on Clark County houses
- Shingles. Usually 12 inches tall by 24 inches wide, straight or wavy bottom edge, a pressed wood grain or a smooth face, face nailed with two or three nails near the bottom. Gray from the factory, nearly always painted by now.
- Flat sheet. On enclosed porches, carports, gable ends, and the lower walls of garages. Smooth, hard, often with battens over the joints.
- Corrugated panels. On shop, barn and shed roofs and sometimes walls, gray and heavy, the same material as the shingles.
- How it behaves. It rings like tile when tapped, it never rots or warps, paint peels off it in sheets, and a chipped corner shows a white, chalky, fibrous edge.
The years that matter
Cement asbestos siding was a mainstream product from the late 1930s until the early 1970s, when manufacturers dropped the asbestos. That lines up with the postwar building boom in Vancouver, Hazel Dell, Camas, Washougal, Longview and Kelso, and with the first reside of the older houses in Hough, Arnada and the Old West Side. About 38 percent of Vancouver’s housing predates 1980. A house built after about 1985 with a similar looking board is nearly always modern fiber cement with no asbestos. The years in between are where a sample earns its keep.
How a sample is taken
- Pick a spot that is already damaged, or an edge behind a downspout where a missing corner will not show.
- Wet the spot with a spray bottle of water and a drop of dish soap.
- Break off a piece about the size of a quarter with pliers, over a wet rag, without sanding or sawing.
- Seal it in a zip bag, then in a second bag. Label it with the address, the wall, and the date.
- Wipe the area and the pliers with the wet rag and bag the rag with the sample.
- Deliver or mail it to an accredited lab. Results in two to five days by email.
We take samples on the same visit we measure, which is usually the simplest path. If you take your own, the Southwest Clean Air Agency’s siding procedure describes it the same way.
Reading the report
The lab report lists each sample, the material description, the method (PLM, sometimes with point counting), and the asbestos content by mineral type. Chrysotile is what cement siding contains. A result above 1 percent makes the material regulated in Washington and triggers the notice, the certified contractor rule for anything not owner occupied and owner performed, and the disposal requirements. A result of none detected means any siding contractor may remove it like ordinary siding.
The good faith survey rule
Washington Labor and Industries requires a good faith inspection by an accredited inspector before any construction, renovation or demolition that could disturb suspect material, with the written report shared with every contractor and worker on the job before work starts. Fines can reach $600 per day for skipping it. Work in your own residence that is not used commercially is exempt from the general survey rule, though you still have to tell any contractor you hire what is there. For a rental, a flip, a commercial building, or a job with other trades on site, the survey is required and we can arrange it through an AHERA accredited inspector; the Southwest Clean Air Agency keeps a list of inspectors for the district.
What a positive result means for the price
A positive result does not change the per square foot rate on our cost guide; it confirms the job is the regulated kind the rate was written for. What moves the number after the test is the measurement: how much of the house is actually cement board, how high it goes, and whether there is a second layer under it.