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"Roofing underlayment was originally used
for temporary protection against the elements but is now an integral
part of a home's overall roof system. Underlayment provides a vital
second layer of protection on top of the sheathing to help keep
moisture out. It is necessary for roofing manufacturers' warranties
and is now considered a necessary piece of the roofing puzzle. State
and municipal codes require roofing underlayment for the system to
meet standards like fire resistance, wind uplift resistance, puncture
resistance, and resistance to wind-driven rain.
The choice of one underlayment over another depends on a number of
conditions, including its application, whether it will be used on a
steep or low-slope roof, the fire code requirements in place, and in
what region the structure is located. Fortunately for consumers and
roofing contractors, there are many underlayment manufacturers on the
market. Underlayments fall under three basic categories: felts,
synthetics, and self-adhering ice-and-water barriers."
Bob Vila
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Self-adhering
underlayments were
initially used primarily in New England, where ice damming threatens
roof integrity. These self-adhering ice-and-water barriers were
installed mainly in the valleys and eaves of the roof, where ice
damming tends to occur. An ice-and-water barrier is significantly
thicker than felt or synthetic underlayments, is seamless, provides
top-rate water protection, and requires no fasteners for installation.
When an ice-and-water barrier is used in a roofing system, it is
applied as a first layer, with the felt paper or synthetic
underlayment applied on top, across the entire roof deck. These
self-adhering underlayments are designed to seal up around any nails
or staples used to install the felt paper, synthetic underlayment, or
roof shingles. "Self-adhering underlayment works great on low-slope
applications where water tends to pool up, says Jones." The
underlayment does not allow the water to seep through."
Asphalt-Saturated
Felt—The Grandaddy of Underlayments
Also called builder's felt or felt paper, asphalt-saturated felt has
been covering roofs for more than 50 years. The felt is made of a
paper base that is impregnated or saturated with asphalt to make it
more resistant to the elements. Some papers are actually coated in
asphalt, while others are truly saturated. Roofing paper or felt is
rolled across a roof deck and stapled or nailed in place. Builder's
felt differs by weight and may be No. 30 or No. 15 felt, a reference
to the original weights of each underlayment. "The name changed
because today's 15 lb. felt is actually lighter than it used to be,
because of modern technology and production," says Joan Crowe,
technical manager of the National Roofing Contractors Association in
Illinois. Although inexpensive and fairly easy to install, felt paper
can be susceptible to tearing, especially in hot temperatures, and
makes for a slippery surface to walk on while installing the roof
covering. Asphalt felt also tends to trap moisture within the roofing
system since it does not breathe.
Synthetic
Underlayment—A Growing Trend
Much newer to the market are the polypropylene underlayments that are
making waves in the roofing world. Made of synthetic polymers, the
exact composition of these underlayments varies from manufacturer to
manufacturer and remains strictly proprietary. These synthetic
underlayments are marketed as wrinkle-free, tear resistant, and safer
for workers to walk on during installation. "Synthetic underlayments
are generally more durable than asphalt-saturated felt," explains
Crowe. They are more expensive than felt, but it may be that you get
what you pay for. "Synthetic underlayments are more breathable," says
Tom Jones of Stevens Roofing Corp. in Norfolk, Virginia. "They are
waterproof, but they also allow moisture to pass out of the system."
As a result, synthetic underlayments are mold resistant. They are
lighter weight than felt papers, are lighter in color for a cooler
roof, and are typically sold in greater widths and lengths. This
translates into labor and time savings for roofing contractors.
Complete
Systems—A Growing Trend
Warranty is a key word when it comes to roofs. Depending on location,
a high-end slate or metal roof might cost as much as $400 per square
foot to install. This is a hefty chunk of change to dish out at one
time. Homeowners want to know that a manufacturer will back up the
product with a warranty and that a roof said to last for 30 years will
actually do so or be replaced. Manufacturers are now marketing
complete roofing systems, which allows them to offer longer and
more-comprehensive warranties. "Manufacturers want you to buy their
whole package, including weather barrier, underlayment, and shingles,"
Crowe says. "If you use the whole package, you'll get the total
warranty."
While the definition of total warranty will vary from manufacturer to
manufacturer, the phrase is enough to convince most roofing
contractors to buy into it. "When we do a roof, we tend to go by the
manufacturer's recommendations and use their complete system," Jones
says. "That way we know we can go back to the manufacturer if there is
a problem with the roof later on, because they've provided a bit more
extended warranty."
Marketing trends aside, the advancements being made in roofing systems
and roofing underlayments are leading to stronger, longer-lasting
roofs that hold up better against the worst that nature has to offer.
"The new technologies have solved a lot of problems," Jones says.
"These advancements are good for the industry."

Shingle Quality: When a roof can account for as much as 40%
of the average home's exterior, many factors weigh into the choice of
materials. Some surfaces are more beautiful than others. Some offer
greater resilience or endurance. Some are more affordable. But the
one roofing surface which offers all those attributes in balance is
the asphalt shingle.
Now
accounting for about 80% of the residential roof surfacing in the
United States, asphalt
shingles are measured against a variety of standards that evaluate
fire
and wind resistance, tear strength, and other key performance
indicators. For fiber glass shingles, ASTM D3462 is considered the
most important.
This comprehensive
standard covers tear strength, nail-pull resistance and pliability,
among other shingle characteristics.
Over 20 CertainTeed
fiber glass shingles are independently certified by Underwriters
Laboratories to meet the tough ASTM D3462 standard.
Underlayments are an important part of
roofs in Seattle as are the other components. All to often Seattle
homeowners become fixated on the roof shingles at the expense of the
roofing system. It is important to find a contractor who understands
the components and importance of the roof systems of Seattle because
we have geographic stresses that are unique to our area. Roof
contractors on the Eastside (Kirkland, Bellevue, Issaquah and
surrounding cities) are begining to find the benefits of installing a
premium roof system. This has not always been the case since shingle
technology has blossomed over the last twenty years and even more so
over the last 10. |