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Carpet padding types, properties, uses: this article explains carpet padding, cushions, and underlayment as well as antique carpet liners, and we address questions about carpet asbestos or mold hazards.
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Carpet padding, carpet cushions, and carpet underlayments, used to improve carpet durability, prevent carpet movement, and for other purposes, can also be a source of hidden mold or other building contaminants.
Some readers have also asked if carpet padding is likely to be an asbestos hazard in buildings, as we discuss and illustrate here.
Question: Does asbestos flooring or carpeting underlayment resemble foam?
Does asbestos flooring or carpeting underlayment resemble foam? Is it a paper like product? - D.G.
Sorting Out Reports of Asbestos-Contaminated Carpet Padding in Western Australia
An exception of asbestos-contaminated carpet padding has been reported in Australia, creating a public stir, but a subsequent investigation by Jim Dodd, Director of Environmental Health, reported that the possibility of asbestos fibres being in carpet underlay was very low. People most at risk were those working in the bag recycling industry when hessian (burlap or jute) bags used to transport asbestos material were recycled. Western Australians concerned about possible asbestos in their carpet underlay should first identify the type of carpet padding used: for example if it is a foam product it was not made from recycled bags.
Quoting from "Asbestos in Carpet Underlay", from the Western Australia DOH,
The DOH offered this good advice for removing old carpeting and carpet padding or underlay:
Owners concerned about possible asbestos in their fiber-based carpet underlay should contact an accredited asbestos testing laboratory.
List of Carpet Padding Materials
Normally carpet padding is constructed of man made or natural fibers, rubber, or urethane foam products. Unlike the backer on some resilient flooring products or sheet flooring, carpet padding would not normally contain asbestos. Carpet padding materials are typically felt carpet padding (photos above), foam carpet padding (photos below), or synethetic fabric bonded to a foam underlayment.
Fiber carpet cushions or pads (above) may be made from natural fibers (such as jute, felt, or even horsehair), synethetic fibers (acrylic fibers, nylon fibers, polyesters, propylene fibers), or recycled textile fibers that may be a mix of natural and synthetic materials.
Bonded Synethetic Fabric & Foam Carpet Padding
Our photos below illustrate a durable carpet cushion that combines a dense synethetic fabric with a urethane foam cushion. While this material is sold for use under wall-to-wall carpeting, we also use this padding cut to size for placement under area rugs where we want a firm walking surface and an anti-slip property to prevent the rug from moving.
Bonded Urethane Foam "Rebond" Carpet Padding
The carpet padding photographs below show a bonded urethane foam product also referred to as "rebond" because it is made of chopped or shredded foam that has been re-bonded together to form a sheet. At below left you can also see the bonded coated backing of the carpeting itself - the white-coated carpet bottom at the right side of the photo.
Our second rebond padding photo (below right) shows us exposing the subfloor below the padding in an area where the homeowner had already made carpet and padding cuts to inspect for water leakage.
At left you can see that the rebond carpet padding is also reinforced with synthetic fibers.
Because some rebond, especially made in the U.S. before 1985, may contain butylated hydroxytoluene (BHT), this padding type can cause yellowing of olefin and some nylon carpets and is not recommended below those products.
Two other foam carpet padding materials are prime urethane foam and mechanically-frothed urethane foam.
Rubber carpet padding materials are typically seen in one of two forms: waffled sponge rubber and a more firm flat sponge rubber. Flat sponge rubber is used below commercial and berber carpets.
Wanamaker's Sanitary Carpet Lining - Antique & Historic Carpet Underlayment, Lining, Padding
In older homes and some historic properties where very old carpeting remains, you may find paper-based Sanitary Carpet Lining that was sold by The Wanamaker Store (photographs below). We are uncertain of the composition of this material, but you are highly unlikely to encounter it except in an antique building. Wanamakers, a Philadelphia PA store, began 1880, selling carpets and carpet liners in 1880.
Note: The John Wanamaker Store in King of Prussia, PA. has been cited by some asbestos-exposure and mesothelioma websites as a source of asbestos exposure to workers. We have not [yet] located a description of how that exposure occurred or what products were involved.
Watch out: in older homes in Australia, carpet padding may have been produced by recycled bags used by James Hardie corporation to transport asbestos fibers, creating an unexpected potential asbestos hazard in those homes. Also in Australia, both driveways and garage floors of some homes built int he 1970's may have contained asbestos waste from James Hardie.
There were however many other that used asbestos paper such as HVAC duct wrap and asbestos backing on sheet flooring. Please keep in mind that no one can assure by email that your property has no asbestos present. If the property age or other conditions raise an asbestos concern, you should have a professional inspection and tests performed.
See our articles on visual identification of asbestos products in buildings, beginning at ASBESTOS IDENTIFICATION IN buildings
Moldy or Smelly Carpeting & Carpet Padding Odors
Carpeting that has been wet usually is removed along with its padding and disposed of, though we have found a few cases in which carpet that was reported to have been wet was dry, un-stained, and clean at the time of our inspection.
We attribute this last odd case to occupant reporting errors. It's generally the case that a soaked carpet will also leave water marks on the subfloor below.
No water clues were present in the "clean carpet" case.
Excepting that odd occasional case, wet carpeting and carpet padding can become moldy in just 48 hours or so, depending on building temperatures and extent of water intrusion. If you trace a moldy odor or smell to the carpeting (see SMELL PATCH TEST to Track Down Odors) or its padding beneath, chances are that it is or was moldy.
Carpets or Carpet Padding & VOCs or MVOCs
As we discuss at CARPET MOLD CONTAMINATION, mold may be visible on the surface of carpeting or mold may be hidden in carpeting or in the padding or carpet cushion below.
Carpets may not actually be mold contaminated but can smell moldy if the carpeting or padding have absorbed Mold-related volatile organic compounds or MVOCs. In this case we suspected that the visible carpet mold was the "tip of an iceberg" of hidden mold below.
For a discussion of carpet padding odors and possible IAQ concerns, Carpeting VOCs, styrene, 4-PC & Formaldehyde and VOCs from Carpet Padding & Carpet Adhesives see CARPETING & INDOOR AIR QUALITY.
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