How do I know if my siding contains asbestos?

Rigid, brittle cement-like shingles about 12 by 24 inches on a house sided between the 1920s and 1970s are the classic sign. Only a laboratory test of a sample taken by a trained inspector can confirm it. Do not break off a piece yourself.

Is asbestos siding dangerous to live with?

Intact asbestos-cement shingles in good condition release very little and are generally left alone. The risk comes from breaking, drilling, sanding or power-washing them.

Can new siding be installed over asbestos siding?

In many places, yes, if the shingles are intact and local rules allow it. Installers fasten the new siding carefully to avoid breaking the old shingles. Ask your municipality and contractor before deciding.

Do I need a special contractor to remove asbestos siding?

It depends on your state and county. Federal NESHAP rules do not cover single-family homes, but some counties, including Allegheny County and Philadelphia, have their own rules, and workers are protected by OSHA rules. Ask your local health department.

Asbestos Siding: What Homeowners Need to Know

What asbestos siding is

Asbestos-cement siding is made of Portland cement reinforced with asbestos fibers. It was sold as a fireproof, rot-proof, paint-holding alternative to wood and was widely used on houses from the 1920s through the 1960s; builders were allowed to use up existing stock into the early 1980s. It usually came as rectangular shingles about 12 by 24 inches, installed in overlapping rows, often with a wavy lower edge or a textured, wood-grain or dimpled surface.

In the older neighborhoods of Pittsburgh, Cleveland, Youngstown, Johnstown, Erie, Philadelphia’s inner suburbs and the Detroit suburbs, it is very common – and often invisible, because later owners covered it with aluminum or vinyl.

How to recognize it

Shape: hard, flat or slightly textured shingles in a regular pattern, often with a wavy or straight bottom edge and exposed nail heads near the bottom
Material: thin (about 3/16 inch), stiff and brittle; it does not bend like vinyl or dent like aluminum
Sound: tapping with a hard object gives a sharp, ringing sound, similar to ceramic tile
Broken edges: a chipped corner looks gray, rough and fibrous
Age: a house built or re-sided between the 1920s and the 1970s

Looks can be misleading, because fiber cement products made since the 1980s use cellulose fibers instead of asbestos and look similar. The only way to know for sure is a laboratory test of a small sample, taken by a trained inspector. Do not break off a piece yourself.

Is it dangerous?

Asbestos is a health risk when its fibers are released into the air and inhaled. In asbestos-cement siding, the fibers are bound in cement, so intact shingles in good condition release very little. The guidance from environmental agencies is consistent: if asbestos-containing material is in good condition – not peeling, cracking or crumbling – leave it alone. The risk comes from breaking, sanding, drilling, cutting or power-washing the shingles, which is exactly what happens when siding is removed carelessly.

What the rules say

The rules are different for private homes and for larger buildings, and they differ by state and county:

Federal rules. The EPA’s asbestos NESHAP, which sets notification and work-practice rules for renovations and demolitions, does not apply to residential buildings with four or fewer dwelling units. EPA has stated that other federal, state or local rules may still apply.
Pennsylvania. State rules follow the same idea for single homes, but Allegheny County and Philadelphia have their own additional rules for renovating and demolishing buildings that contain asbestos. Some municipalities publish their own guidance – the City of Johnstown, for example, asks owners to check for asbestos before renovation or demolition and to contact the city about local rules.
Maryland. The Maryland Department of the Environment publishes a homeowner FAQ explaining when homeowners may handle asbestos themselves and when licensed contractors are required.
Workers. Even where homeowner rules are loose, contractors’ crews fall under OSHA worker-protection rules, which is one reason professional removal costs more than tear-off of ordinary siding.

Because the rules vary, ask your municipality or county health department before work starts, and mention the asbestos siding when you call a contractor.

Your options when you want new siding

Leave it and cover it. Where local rules allow it and the shingles are intact, many installers attach new siding over asbestos-cement shingles. They install furring strips or foam board and fasten through carefully, or use methods that minimize drilling and breakage. This avoids disturbing the shingles and usually costs the least. The downside: the asbestos stays in the wall, and a future owner or renovation will have to deal with it.
Remove it properly, then re-side. Shingles are wetted, the nails are cut or pulled so shingles come off whole, and the pieces are wrapped and disposed of as asbestos waste. Done right, this lets the installer inspect and repair the sheathing and add a new weather barrier – the best result for the wall, and often a plus when you sell. It costs more and takes longer.
Repair and paint. If you only want to keep the house in shape for now, broken shingles can be replaced with non-asbestos lookalikes and the siding painted. This does not solve the problem long term but avoids disturbing it.

Asbestos is only one of two hazards on older homes: if the house was built before 1978, the paint on the shingles or trim may contain lead. Under the EPA’s Renovation, Repair and Painting rule, a contractor who disturbs more than 20 square feet of painted exterior surface on a pre-1978 home must be an EPA-certified firm.

Questions to ask a contractor

Have you worked with asbestos-cement siding before, and which option do you recommend for my house?
Will you test the siding first, and who takes the sample?
If you remove it: who does the removal, how is the waste disposed of, and is that in the written price?
If you cover it: how will you fasten the new siding without breaking the shingles?
Are you an EPA lead-safe certified firm (for pre-1978 homes)?
In Pennsylvania: what is your Attorney General registration number?

Found under vinyl or aluminum? How it usually comes to light

Many homeowners only learn about asbestos shingles when an installer lifts a panel of the newer siding. That is why it is worth asking for a small inspection opening before you sign a contract on an older home: the contractor removes one piece of vinyl or aluminum in an inconspicuous spot and looks at what is underneath. If the layer below looks like cement shingles, the price and method can be settled up front instead of in the middle of the job, when the old siding is already half off.

Other clues are the age of the house, the depth of the window trim (several layers push the siding out from the window frames) and the paperwork from earlier renovations or a past home inspection report.

Do’s and don’ts until the siding is replaced

Do leave intact shingles alone and paint them if they need protection
Do tell anyone working on the outside of the house – painters, electricians, satellite installers – that the siding may contain asbestos
Don’t power-wash, sand, scrape or drill asbestos-cement siding
Don’t break off a sample yourself or throw broken pieces in household trash
Don’t let an installer rip the shingles off with a pry bar and toss them in an open dumpster

Does asbestos siding hurt a sale?

Home inspectors routinely note suspected asbestos siding in their reports. Intact shingles are usually not a deal-breaker, but they can lead to questions and negotiations. Buyers are often more comfortable with a house that has been professionally re-sided with the old material removed, or where the seller can document how it was handled.

Asbestos siding: how to recognize it and what your options are