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Roofing Underlayments - FAQs
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It is up to the contractor and specifier to
decide what level of performance is required based on the guidelines that
we provide. In essence, if the project demands a high level of protection
from long lasting or large ice dams, then Grace Ice & Water Shield®
is the appropriate choice. This would provide maximum protection in areas
of the country that experience snowy winters. Where winters are generally
mild but will still experience wind driven rain, or where code based minimum
standards of protection are required, Grace Ice & Water Shield® can
offer sufficient protection. If it is expected that the roof will be subjected
to very high temperatures for extended periods of time, then Grace
Ultra should be the product of choice.
You can use Grace Underlayments as an underlayment
for all commonly used roofing materials including asphalt shingles, slate,
tile and metal roofing systems. However, check with the metal roofing
manufacture for any special requirements.
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Copper, Cor-Ten® and zinc metal roofing
have inherent properties that cause roofs constructed with these materials
to become exceptionally hotter than other roofs. These metals absorb most
of the energy reaching them from the sun (high thermal absorption), reflect
little energy (low reflectivity), and conduct heat very rapidly (high
thermal conductivity). Therefore, there are special design considerations
for underlayments used under these metal roofs, due to the high in-service
temperatures that these roof assemblies can reach.
Grace Ultra is recommended for use under copper,
Cor-Ten and zinc in high altitude climates. Grace Ultra is formulated
with an adhesive based on butyl technology and is designed to withstand
even the highest in-service roof temperatures. This membrane provides
the highest factor of safety in high temperature roof applications.
Check with your Grace representative.
Some architectural metal roofing systems require
that the seams between panels be welded. If the architectural metal is
applied directly over the membrane it is possible that the heat from the
welding operation could cause damage. The Grace underlayment should be
adequately protected from the heat of the welding process. What constitutes
protection will depend on the type of metal, the type of torch, and the
seam system being used. In some cases, contractors have found that two
layers of 6.8 kg (15 lbs) roofing felt, placed only in the metal seam
area, offered sufficient thermal protection from a welding operation.
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Grace underlayments are not meant to
be left permanently exposed to the sun. In general, the membrane should
be covered with the final roof covering as soon as possible. However,
Grace underlayments may be left exposed as described below, if necessary,
to accommodate construction scheduling or weather problems.
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Grace Underlayment
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Maximum Exposure
Period |
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Grace Ultra |
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60 Days |
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Grace Ice & Water
Shield® |
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30 Days |
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Grace Select
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7 Days |
Most caulks and sealants are compatible with
the polyethylene coating on the face of the underlayment However, the
adhesive side will react with caulks and sealants that contain hydrocarbon
solvents, polysulphides, pentachlorophenol, creosote, and gasoline/oil
as well as EPDM and uncured neoprene sheets. Care should be taken if using
these compounds so that they do not contact the adhesive.
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No. Felt will act as a bond-breaker to the
substrate. Grace underlayments are intended for application directly to
the structural deck. Grace underlayments can be applied over existing
Grace underlayments in a reroof application.
The drip edge should be installed over the
underlayment.
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Yes. Grace Ice & Water Shield, Grace Select
and Grace Ultra are vapor barriers. In full coverage applications, proper
ventilation is necessary. When used in conjunction with metals that are
particularly susceptible to corrosion, such as zinc, care should be taken
to allow a means of escape for water that becomes trapped between the
membrane and the metal.
The most obvious difference is that while Grace
Ice & Water Shield is 40 mil thick, Grace Select is only 25 mil thick.
Grace Ice & Water Shield is designed to offer premium protection from
leaks caused by ice dams in all climates, clearly surpassing many of the
minimum standards of performance set by ASTM, ICBO and SBCCI. Grace Select
is designed to meet the code-based standards of performance. Grace Select
is also significantly lighter weight than Grace Ice & Water Shield making
it easier to handle a full roll.
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Grace Ice & Water Shield is well recognized
as the premium performance underlayment on the market today. However,
on some projects, all the performance that Grace Ice & Water Shield offers
may not be needed. If the project is in a mild climate area, or if the
specification is driven purely by code minimum standards of performance,
the premium nature of Grace Ice & Water Shield may be more than is necessary.
Grace Select offers contractors and specifiers the opportunity to choose
products with appropriate performance for the specific projects they are
working on. Grace Select is part of the Grace underlayments family of
products, which includes Grace Ice & Water Shield, Grace Select and Grace
Ultra. Each product is uniquely suited for specific roofing applications,
making it the most complete line available.
Yes. Grace Select meets the key performance
standards for fully adhered underlayments in severe climates prescribed
by ASTM and ICBO and has an ICBO Evaluation Services Report (No. 3997).
Grace Select also has a UL Class A fire classification under fiberglass
shingles and a Class C under organic felt shingles.
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The main difference between Grace Ice & Water
Shield and Grace Ultra is that while the adhesive in Grace Ice & Water
Shield is based on SBS rubber, the adhesive in Grace Ultra has a butyl
rubber base. There are other differences as well. Grace Ultra may be left
exposed to the sun for up to 60 days, and it is slightly thinner at 30
mil than Grace Ice & Water Shield, which is 40 mil thick.
Stated simply, butyl rubber offers exceptional
stability at high temperatures. In some roofing applications, such as
those in the desert southwest, roof temperatures can get high enough that
SBS based adhesives can flow under the extreme heat. Butyl rubber based
membranes remain stable for long periods of time even at extreme roof
top temperatures.
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Grace Vycor Plus Self-adhered Flashing is designed
to provide superior protection against water, air and moisture infiltration
around window and door openings, corner boards and other critical wall
penetrations. Grace Vycor Plus is 25 mil thick and is available rolls of 4",
6", 9, and 12" to accommodate a variety of job requirements. It should
not be installed on roofs.
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