A roofing underlayment is a rubberized membrane that goes under
shingles to prevent water penetration. It is the one piece of a roofing
system that is expressly designed to be waterproof. Without an
underlayment, water from wind-driven rain or ice dams can infiltrate
under your shingles and severely damage your roof—or even worse, the
inside of your home.
Grace roofing underlayments, widely regarded as
the best in the industry, offer premium waterproofing protection.
is an excellent article on roofing underlayments which outlines the
function, design considerations, and current NRCA recommendations for
the use of underlayments with your average steep-slope roof.
Steep-slope roof systems require different underlayment installations
Since 1981, The NRCA Roofing and Waterproofing Manual has contained
underlayment recommendations in its steep-slope roofing section.
Although these recommendations have evolved during the years, some
basic design principles have remained the same. For instance, different
steep-slope roof coverings require underlayments that correspond with a
roof covering's anticipated service life and roof slope. Because of the
many variations possible, I will discuss the function, design
considerations and current NRCA recommendations for the use of
underlayments with different steep-slope roof coverings.
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Ice dams form when warmth from inside the home melts the bottom layer
of snow on the roof, sending water trickling down to the edge. Exposed
to frigid air, it immediately refreezes, clogging gutters and causing
the water behind it to pool up and find a path into the home below,
usually through the shingles. Ice dams are more common in older or poorly
insulated homes and those with low-pitch roofs. But even in newer homes,
a new roof can leak if water runs backward in between the shingles.
Wind Driven RainWind-driven rain can cause sloped roof coverings to shift and lift.
Rain can then be easily driven under the roof covering directly to the
unprotected roof deck, where it causes leaks and damage to the inside
of the home. Follow this link to see an illustrated example of wind
Grace Ice & Water Shield®
The leading self-adhered roofing underlayment, Grace Ice & Water Shield offers premium leak protection for sloped roofs in climates subject to ice dams and wind-driven rain. It is applied to the roof deck prior to the application of the finished roof covering, which is most often shingles but can also be tile or metal. The membrane goes under shingles and seals around nails that hold the shingles in place, so water that doesn't drain properly cannot penetrate the roof. It also creates a weather-tight barrier against wind-driven rains that cause shingles to lift and leak. Affordable and easy to install, it provides added peace of mind for many years, even in the most brutal winters.
Grace Ultra protects sloped roofs from the effects of wind-driven rain and ice dams in climates that experience high temperatures over extended periods of time. This underlayment offers excellent performance at elevated temperatures, in hot desert southwest climates, or any place that requires superior heat resistance.
Grace TRI-FLEX 30®
Grace TRI-FLEX 30® is an innovative spunbonded polypropylene coated with a layer of U.V. stabilized polypropylene on both sides. This technology, available only from Grace, creates a very durable and tough weather resistant fabric. It has excellent tear resistance, designed to withstand even the strongest wind conditions.