What is Roofing Felt?
Roofing felt is a building material that is essentially a thick paperboard product saturated with asphalt. It is supplied in rolls, and is often coated with mineral grit on both sides to keep the layers from sticking together. It comes in several weights, with 15-lb. being commonly used.
Some types of roofing felt have at times been made with asbestos paper. The use of asbestos added to the moisture, pest, and flame-resistance quality of the roofing felt material. Asbestos roofing felt can be used under shingles to provide a moisture barrier, but is more frequently used to construct a "built-up" flat roof system.
Who Works with Roofing Felt?
Roofing contractors, including union workers, who installed roofs during new construction or renovation projects, and repaired existing roofs frequently, used asbestos containing roofing felt. Maintenance workers responsible for the upkeep of flat deck roofing systems may have also used roofing felts for patching and maintenance. Demolition workers, homeowners, and hardware store employees may have also handled roofing felts containing asbestos.
Where is Roofing Felt Found?
Roofing felt may be used on many types of buildings, including private homes, but is mainly found on larger buildings with flat deck-type roofs. Hospitals, schools, warehouses and large retail stores are examples of the type of buildings which may have a roof constructed with roofing felt. These roofs are built up by hot-mopping asphalt over a layer of roofing felt and repeating until the desired thickness is achieved. A top coat of light-colored gravel is often used to reflect heat.
How Does Roofing Felt-related Asbestos Exposure Occur?
Roofers installing new roofing can be exposed to asbestos in the process of tearing or cutting lengths of roofing felt. Rolls of felt may become damaged in storage or transport, releasing asbestos fibers into the air. Built-up roofing is made by alternating several layers of roofing felt and asphalt to a desired thickness. Gravel and sealants may be added as top coats to deflect heat and moisture. Some roofing cements, base sheets and sealants also contained asbestos.
Built up roofing can deteriorate with age and exposure to the elements. Heat from the sun can cause the asphalt layers to blister and separate from the felt. Repairs involve cutting into the blistered area, and inserting a felt patch. Other conditions of wear may include brittleness and cracking, which can release fibers and require new applications of felt and asphalt to repair damaged areas. Water, ice and snow can also contribute to deterioration and friability in a built up roof causing exposure to dangerous asbestos fibers.
Common Diseases Associated with Asbestos Exposure
The link between asbestos exposure and pulmonary disease was not firmly established until the mid-1970's. Workers responsible for handling asbestos roofing felts and other workers or supervisory personnel who worked in the general vicinity, may have inhaled airborne asbestos fibers while at work, putting them at significant risk for developing one of these diseases: pleural mesothelioma, peritoneal mesothelioma, asbestos cancer and asbestosis. In addition, workers often brought asbestos fibers home on their work clothes which also put their family members, especially women, at risk for developing one of the above diseases. A disease like mesothelioma, can sometimes take 30 or 40 years following initial asbestos exposure to develop (i.e. long mesothelioma latency period). The mesothelioma prognosis for those diagnosed with the disease is generally not favorable.
Roofing Felt Products Containing Asbestos
The following partial list of roofing felt products were known to contain asbestos:
|Product Name||Start Year||End Year|
|Fibreboard Roofing Felt|
|GAF Asbestos Base Felt Roofing|
|Johns Manville Asbestos Roofing Felt|
|Johns Manville Blue Chip Felts Roofing Felt||1907||1979|