Fundamentals of Black Mastic Asbestos and Its Removal

With more than 20 years of practical experience in renovating, repairing, and enhancing residences, Lee has been offering home improvement guidance for many years.

When you take out old linoleum or vinyl flooring, you may notice dark adhesive smudges between the tiles and the subfloor. These dark marks could be black mastic, an outdated construction material that may contain asbestos. Removing black mastic can pose health risks, but it is generally deemed harmless if it is not disturbed. Discover more about black mastic asbestos, its appearance, its common locations, and the appropriate steps to take if you encounter it.

What is Black Mastic Asbestos?

Mastic refers to a category of adhesive that has a glue-like consistency. Contemporary mastics are typically formulated with latex or are water-soluble, allowing them to be reactivated with water. In contrast, traditional asphaltic cutback adhesive is a vintage form of mastic that utilizes asphalt-based cement. The presence of asphalt gives this mastic its characteristic black hue. Asbestos was incorporated into the mastic primarily to enhance its strength, rather than for fire resistance.

How Can You Identify Black Mastic Asbestos?

Black mastic asbestos becomes visible only after the removal of the flooring. True to its name, its main hue is black, although remnants of other colors might be visible, possibly from the underlying subfloor or from sections of the flooring that were not entirely taken out.

Typically, black mastic adheres smoothly to the subfloor, presenting a uniform surface without notable ridges, bumps, or gaps. It may display subtle, ingrained patterns resembling comb marks or swirls from the original application process.

Interesting Tidbit

Mastic is a term that has fallen out of common usage, yet you might still come across it if you have some old cans stored away at home.

Worries Regarding Asbestos in Black Mastic

Certain black mastics may contain asbestos, although not all do. Asbestos is known to be a cause of a serious illness known as mesothelioma.

Before taking any action with black mastic in your residence, it’s crucial to recognize it and handle it correctly.

Cutback

Cutback refers to a type of flooring adhesive made from asphalt that is resistant to water and does not become soft when exposed to moisture.

Certain cutback adhesives included asbestos. It is widely believed that asbestos was incorporated into these mixtures for its fire-resistant properties. Although this would provide some level of fire protection, the main reason for adding asbestos was to enhance the durability of the product. Asbestos is a fibrous substance, and its fibers interweave to reinforce mastic, insulation, and various other construction materials used in homes.

Locations of Black Mastic Asbestos

In the past, all resilient flooring was attached directly to the subfloor with glue. Although adhesive-only flooring remains an option for areas like kitchens and bathrooms, and offers certain benefits, the most prevalent choices today are floating flooring and self-adhesive flooring.

Widely utilized in residences constructed during the 20th century, black mastic served as a bonding agent for ceramic tiles, linoleum, vinyl, and various other durable flooring options.

Tip

Certain older water-based latex adhesives were also black, meaning that color by itself is not a dependable feature for identification.

Asbestos fibers in the mastic will not be detectable to the naked eye. Although cutback mastic is resistant to water and various cleaning agents, aggressive sanding (which is not advisable due to the risk of asbestos exposure) can cause it to become dense and tar-like due to the heat generated.

How to Confirm the Presence of Black Mastic Asbestos

Black mastic adhesives, which can contain anywhere from 1% to 25% asbestos, were primarily produced during the early to mid-20th century. Residences constructed prior to the 1950s are more likely to contain black mastic asbestos, although it may also be present in homes built up until 1986.

The most reliable method to determine if black mastic contains asbestos is to conduct a test. There are DIY asbestos testing kits that allow individuals to scrape a sample, place it in a plastic bag, and send it to a lab for analysis.

If testing the material in question isn’t feasible, one alternative method to determine if the mastic has asbestos is to search for an old can. In numerous older homes, you can often discover vintage cans of paint and adhesives tucked away in attics, basements, beneath staircases, in sheds, or even left behind in the yard.

How to Handle Black Mastic Asbestos

Black mastic asbestos poses no danger when it remains undisturbed and properly encapsulated. However, it becomes hazardous when it is damaged, releasing fibers into the air. Actions like sanding or frequent foot traffic can lead to this deterioration. The safest approach is to leave the material as is and apply a new layer over it.

It is possible to install new flooring on top of existing flooring, as long as the old surface is level and securely attached. Avoid using a drum sander to remove black mastic asbestos from the old flooring, and do not try to scrape it off by hand. Due to its dense and sticky nature, it cannot be safely eliminated. The most effective approach is to leave the old flooring intact and install the new flooring over it.

Producers of Black Mastic Containing Asbestos

• Allied Signal, Inc.
• American Biltrite is a company known for its high-quality rubber products and materials.
• Olean Tile Company from the United States
• Amtico Flooring
• A.P. Green Enterprises
• Armstrong World Industries
• Asbestos Company, Limited.
• Celotex Company
• Combustion Technology
• Congoleum Corporation
• Crown Cork & Seal
• DAP, Incorporated.
• Durez Plastics
• Foster Wheeler Company
• GAF Company
• Garlock Sealing Technologies
• Georgia-Pacific Company
• Hysol Aerospace Company
• Johns-Manville
• Kaiser Gypsum Corporation, Incorporated.
• Kelly-Moore Paints
• Minnesota Mining and Manufacturing Company, commonly known as 3M.
• Mobil Oil Company
• NARCO / Honeywell
• National Gypsum Corporation
• Owens Corning and Fibreboard Corporation

Black Mastic Asbestos Brands

Notable brands of floor adhesive that contained asbestos may include the following. In certain instances, these products are still available, albeit without the asbestos component.

• Armstrong S-89 Bonding Agent
• Armstrong S-90 Bonding Agent
• Atlas Stove and Furnace Adhesive
• Carey Fiber-Based Adhesive
• Empire Ace Fiber-Based Adhesives
• J-M Fiber-Based Adhesive Cement
• Crown Coat Cement
• Gold Bond Lamination Glue

Warning

If you need to take out a subfloor that has black mastic, ensure that it is tested for asbestos, and adhere to all regulations regarding asbestos removal if it is found to be positive.

Is it safe to walk on black mastic?

If you come into contact with it, it is advisable to avoid stepping on black mastic or interfering with it, as this could release harmful fibers into the atmosphere.

In which year was the use of black mastic prohibited in residential properties?

On July 12, 1989, the United States Environmental Protection Agency (EPA) prohibited the majority of products that contain asbestos, such as black mastic.

Is it acceptable to install flooring on top of black mastic?

Provided that the black mastic remains intact and securely bonded to the subfloor, it is permissible to install new flooring on top of it.