Asbestos roofs, as they were
once referred to, present themselves in a variety of styles
and
sizes. Contrary to popular belief, "asbestos roofs and shingles" are not entirely
asbestos. In a matter of fact, the bulk of the composition of most
of these roofing shingles are of mineral fiber and cement and have
asbestos content. This content will vary from manufacturer to
manufacturer. Historically, we have seen test results indicating
asbestos content from around 5% to as high as 35%. Laboratory
testing is the only reliable way to confirm any type of asbestos
content and the percentage of the same. The type of asbestos
generally used in these materials is known as chrysotile asbestos.
This material is commonly referred to as ACRM (asbestos containing
roofing material) or simply ACM (asbestos containing material).
These shingles are also known as “transite” material, or a rigid
board type material made up of mineral fibers and Portland cement
mixtures. The two major differences in the way asbestos is presented
is the friability factor. Being friable means the ability to be, or
become, airborne. One should know that the matrix of transite
material is so tight that it becomes difficult to create a fiber
release instance unless the material is mishandled or in a state of
decomposition. Regardless of how we know them today, they are like
any other potentially dangerous material and require proper care and
handling. (see
historic installation documents )
As a result of different court
case rulings involving these materials, certain regulations have
been enacted to insure that the material is handled in the safest
manner possible. It should be noted that transite material becomes
regulated “when there is a high probability that it could become, or
has become, crumbled, pulverized or reduced to powder by the forces
expected to act on the material in the course of demolition or
renovation”. In other words, hand pressure. If a Category II
transite (a non-friable asbestos containing material with more
than 1% asbestos), which is
what most roofing and siding material will fall under (including asbestos slate), is in good
condition, it can be broken without causing the material to be
regulated. This determination is usually made on a case by case
situation.
The transite material can be worked with in a safe
manner with each state having their own guidelines and regulations.
The EPA also have their rules. At a minimum, the material being
worked with should be kept wet during work and removal, the nails
extracted from the material and the product lowered to the ground
for continued processing/handling. Disposal of all this material
remains a matter to be governed by each individual location and
state and most often the disposal sites are also regulated.
Asbestos products and by-products have been used
extensively in the roofing industry throughout the years. Since the
health related concerns and issues dealing with asbestos have become
apparent, the companies that once used the material in their
products and processes have slowly been reduced, either having
ceased business operations due to increased legal action and
concerns or they have stopped using the material altogether and have
sought out alternative products which will simulate the properties
of asbestos.
It is commonly thought that asbestos was used only
in shingles and siding, yet it was widely used in insulation, felt
underlayments, simulated wood trim, sheathing and other construction
lumber. It was used in cements, mastics, putties and other types of
sealants commonly used in roof applications. It was used in
corrugated roofing and siding material. In many cases, entire attics
were lined with asbestos containing materials.
So it remains imperative that one look and
investigate further than just the initial roof covering when
performing demolition, repair or restoration work on these old
roofs. It also remains important that a working knowledge of the
products and their applications be integrated into any type of
project affecting this material.
Many of the different types of the mineral fiber
asbestos shingles are available today on the roofing market.
Locating and procuring the material will depend on the availability
of the material salvaged and also the availability of skilled
workmen which can perform the type of repairs or other work that may
be needed.
Asbestos has always stood uniquely alone, a rock as
old as the world which has remained virtually immune to the forces
of heat, weather, moisture and wear. It can also be manipulated into
a variety of useful forms and shapes. It is quarried in much the
same way that stone is mined and except for its color it looks like
ordinary rock. It is only after the process of mechanical
manipulation takes place that the extracted fibres can be changed
into the multitude of useful articles used throughout the years.
Having been a mere curiosity of the ages it
eventually became a widely used mineral with a wide range of useful
and technologically related applications. And, as time went on the
eventual dangers of the product also became apparent. Today, while
asbestos still has beneficial and practical uses, the way it is used
and handled has become paramount and any type of handling must be
performed according to the specified standards.
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