Seal of Approval: How to Make the Most of Asphalt-shingle Sealants

Extreme weather events, such as the wide temperature swings during the recent winter and hurricanes that afflict coastal regions, have increased consumer demand for reliable and high-performance roofs. Asphalt-shingle roofs have been proven to provide the protection homeowners need, thanks to the material’s durability and longevity.

Many asphalt shingles rely on built-in sealants to provide a solid installation. This sealant material is an asphalt-based, heat-activated, viscous bonding material, which retains adhesion in difficult weather conditions, after the initial bonding of the shingles has occurred. The sealant will fuse the asphalt shingles together when each course is properly attached to the roof deck and previous courses.

IMAGE: Asphalt Roofing Manufacturers Association

Click to view a larger version of this image. IMAGE: Asphalt Roofing Manufacturers Association

The bonding sealant is factory-applied on the front or back side of the shingle, depending on the manufacturer’s design. Heat from the sun activates and softens the sealant, initiating the bonding process. After the bonding of the shingle sealant, the shingles provide a home with superior wind-resistance.

If not installed correctly, the sealant will not be able to do its job, which could result in shingle blow-offs and other performance issues. For the roofer, shingles that are not properly installed and allowed to bond could mean an unwanted call back to the job site. The Asphalt Roofing Manufacturers Association (ARMA) recommends contractors follow these essential steps to ensure asphalt shingles are installed properly the first time and that sealant adhesion is not impeded:

Scheduling: If an asphalt-shingle installation takes place in cold or windy weather, it could impact the ability of the sealant to cure. The sealant cannot bond in cold weather, and the wind could shift the shingles and break the bond before it has a chance to complete the process. Follow manufacturer instructions for cold-weather installation or plan for projects when weather conditions are more suitable.

Roof Deck: Making sure the substrate and roof deck are not damaged or deteriorated is key to maximizing the potential of the asphalt-shingle sealant. If these elements are overlooked, the shingles will not have a solid base for fastener attachment, and the sealant between the shingles could be less effective.

Underlayment: Proper installation of an approved underlayment will provide the appropriate surface for shingle installation and will help manage water. Ice-barrier underlayment materials, compliant with ASTM D 1970, are recommended for use in northern climates where accumulation of snow or ice on the roof is likely. The ice shield provides extra protection from the potential for water damage; this is especially important on reroofs of older homes where the placement or quantity of attic insulation allows heat to flow to the roof.

Accessories: Roofing accessories, such as flashings at penetrations, valleys and changes in direction of the roof, are essential to making sure the sealant can do its job. Roofers should select approved accessories, whether they are drip edges, ridge vents or other architectural details.

Nailing: The actual attachment of the asphalt shingles is where a roofer has the most control over the installation process. It is important to make sure shingles are attached to the deck with the proper type, size and quantity of nails, as well as in the precise location required. Make sure the nails are in the right place by driving them in the indicated “nailing zone.” Always ensure nails used in laminated shingles are driven through the double-thickness overlap area.

Selecting a shingle that meets or exceeds wind-speed requirements in local building codes will help a roof covering withstand windstorms and protect a home. Further, roofers should always follow all building codes and manufacturer installation requirements for shingle applications.

Asphalt shingles are manufactured to provide homeowners with beautiful, affordable and reliable protection for their homes. It is up to the installer to ensure the sealants can do their job by making sure other facets of the proper installation process are followed.

About Mike Fischer

Mike Fischer is codes and standards director for the Washington, D.C.-based Asphalt Roofing Manufacturers Association.

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