Asphalt Shingle Types and Ratings
Asphalt shingles are the most common residential roofing material, installed on approximately 80 percent of homes in North America. Three-tab shingles are the basic type, providing a flat appearance with cutouts that create individual shingle tabs. Architectural or dimensional shingles have a laminated construction that creates a thicker, more textured appearance with deeper shadow lines. They typically carry longer warranties of 30 to 50 years compared to 20 to 25 years for three-tab shingles.
The wind resistance rating of asphalt shingles is critical in areas prone to high winds. Class H rating indicates resistance to winds up to 150 mph, while Class G is rated for 120 mph. Impact resistance ratings from Class 1 through Class 4 measure resistance to hail damage, with Class 4 being the highest. Many insurance companies offer premium discounts for Class 4 impact-rated shingles.
Underlayment and Flashing
Synthetic underlayment has largely replaced traditional felt paper due to superior tear resistance, UV stability, and slip resistance during installation. Ice and water shield membrane is required at eaves in cold climates to prevent ice dam damage. This self-adhering membrane seals around nail penetrations and extends 24 inches past the interior wall line. waterproof coating to protect the foundation. vapor barrier installation in crawlspaces. In valleys, a minimum 36 inch wide strip of ice and water shield provides extra protection at this vulnerable intersection.
Flashing at roof penetrations including chimneys, vents, and skylights must be installed according to manufacturer specifications. Step flashing at sidewalls is interleaved with the siding as the shingles are installed. Counter-flashing covers the top edge of step flashing on masonry walls. All flashing should be corrosion-resistant material such as galvanized steel, copper, or aluminum.
Nailing Patterns
Proper nailing is essential for shingle performance. Each shingle requires four to six nails placed on the nailing line indicated by the manufacturer. Nails must be driven straight with the head flush against the shingle surface. Over-driven nails that penetrate the shingle surface and under-driven nails that leave the head exposed both compromise shingle performance. The correct nail length is 1-1/4 inch for standard applications, with longer nails required for thicker shingles or when installing over existing roofing.