What to Know About Asbestos Siding

Asbestos siding is still found on many homes because asbestos-cement shingles were widely used for more than a century. Since plenty of these shingles remain in place, homeowners often wonder whether they need to be taken off right away.

Learning what asbestos siding looks like and how it behaves can help you decide whether removal is actually necessary.

What Is Asbestos-Cement Siding?

Asbestos-cement siding is a thin siding shingle made from Portland cement mixed with asbestos fibers. The cement holds the fibers together and forms a hard, durable material.

Asbestos is naturally fire-resistant, and it was added to the cement as a reinforcing ingredient that helped strengthen the product.

When materials containing asbestos are cut, sanded, torn apart, or demolished, fibers can be released into the air. Breathing in or swallowing those fibers can create health risks.

How to Identify Asbestos Siding

You can try to identify asbestos siding visually, or you can have a laboratory test a sample.

• Shingle form: It appears in several forms, but it is often shaped like shingles and has shallow vertical grooves.
• Nail punctures: Nails are often visible around the edges, and each row overlaps the row below it.
• Fibrous edges: When broken, the edges tend to look rough, flaky, and sharp.
• Ringing sound: Tapping the shingle with a hammer can produce a sharp ringing noise similar to ceramic tile.
• Testing: A small sample can be sent to a lab for confirmation.

Asbestos Siding vs. Fiber-Cement Siding

Fiber-cement siding can look somewhat like asbestos siding. When broken, it may also show a ragged, fibrous edge.

Replacement shingles made from fiber cement contain no asbestos and are commonly recommended when an old asbestos shingle is missing or damaged.

Origins of Asbestos Siding

Asbestos cement was first developed in 1905 by Johns-Manville, which became a major producer of cement-asbestos materials.

By 1910, homeowners and builders could buy Asbestoside, a trademarked asbestos siding product made by J-M Roofing, a shortened name for Johns-Manville.

Products made with asbestos-reinforced concrete continued to be sold and installed well into the early 1970s.

Flintkote was a widely sold brand of asbestos siding in the United States during the 1930s. It was marketed as “permanently fireproof” and as never needing paint. Asbestos siding was still being sold as late as the mid-1960s.

Pros and Cons

Pros

• Fire-resistant
• Resists insects and rot
• Can resemble wood grain
• Easy to clean
• Less porous than wood

Cons

• Brittle
• Can be damaged by pressure washing
• Hazardous when broken
• Replacement pieces are hard to find
• Refinishing is difficult

Asbestos-cement siding on a house should not automatically be treated as a major problem. Many homes and garages still have it, and the health risk is low when the siding is intact and left alone.

Compared with more porous siding such as wood clapboard, asbestos-cement siding does not absorb paint as quickly, which makes it easier to paint.

At the same time, it is quite brittle and can chip, crack, or break easily. Even pressure washing can damage it if the pressure is high enough, potentially allowing moisture to get in.

Because it becomes dangerous when sawn, sanded, or broken up, repairs can be challenging if replacement asbestos-cement siding is unavailable. In those cases, fiber-cement shingles are usually the safest substitute.

Health Risks of Asbestos Siding

The health dangers of asbestos have been recognized for decades. Inhaled asbestos fibers are clearly linked to lung diseases such as asbestosis and to cancers including mesothelioma.

There is no completely safe level of asbestos exposure. Serious asbestos-related illness usually affects people who had repeated contact with the material through manufacturing or installation work.

Removing Asbestos Siding

Taking off asbestos siding can be more dangerous than leaving it in place. When it remains undisturbed, asbestos-cement siding and other asbestos-containing building materials are generally considered safe enough to leave alone.

Removal is usually best reserved for major renovation work, such as adding onto a house. The job should be handled by a certified asbestos abatement company, which can often be found through a state Department of Environmental Quality list of approved contractors.

In some places, permits are required for removal and disposal. Homeowners may be allowed to do the work themselves, but they must still follow special procedures and disposal rules.

Alternatives to Removal

Covering asbestos siding with new siding is usually safer than removing it. This accepted approach seals in the asbestos material without disturbing it.

If a siding contractor removes an outer layer and finds older asbestos-cement siding underneath, the usual practice is to cover it rather than take it off.

Homes with old asbestos-cement siding enclosed under new siding are generally acceptable to inspectors and real estate assessors, and they rarely affect a property’s value.

Asbestos-Cement Siding Basics

• Homes built between 1920 and the 1960s are likely to have asbestos in cementitious siding tiles.
• Cementitious siding installed after 1973 is very unlikely to contain asbestos. That material is known as fiber-cement siding and does not contain asbestos.
• Asbestos-cement siding tiles do not have to be removed simply because they contain asbestos. There is no legal requirement to remove them, and they do not typically add much, if any, resale value.
• Avoid pressure washing asbestos siding, since it can crack the material. A lawn mower striking it can also cause damage.

Frequently Asked Questions

• Is it safe to live in a house with asbestos siding?

  It is generally safe as long as the siding is left undisturbed. Painting is usually fine, but it should not be cut, drilled, or pried off.

• Is it legal to sell a home that has asbestos siding?

  There is no legal requirement for the seller to remove asbestos siding. Disclosure rules for potential buyers can vary by state.

• What is the best replacement for asbestos siding?

  If asbestos siding is removed, it can be replaced with siding of similar thickness, such as vinyl or fiber-cement siding.

• What is the best way to cover asbestos siding?

  A thin siding product is usually best. Thicker siding can push beyond trim and other architectural details. Vinyl is often a strong choice because it is thin and can last 30 to 40 years.