Definition
The highest impact resistance rating for roofing materials per UL 2218 testing. Class 4 shingles withstand a 2-inch steel ball dropped from 20 feet. Important in Colorado's hail-prone climate and may qualify for insurance discounts.
Related Terms
Algae Resistant Shingles
Shingles manufactured with copper granules that inhibit the growth of blue-green algae, which causes dark streaks on roofs. Common in humid climates but beneficial in Colorado where moisture can collect in shaded areas.
Architectural Shingles
Multi-layered asphalt shingles that create a dimensional, textured appearance. Also called laminated or dimensional shingles. They're thicker, more durable, and more wind-resistant than 3-tab shingles.
Asphalt Shingles
The most common residential roofing material in North America. Made of a fiberglass mat coated with asphalt and surfaced with mineral granules. Available in 3-tab and architectural styles.
Attic Ventilation
The system of intake and exhaust vents that circulates air through the attic space. Proper ventilation prevents moisture buildup, ice dams, and premature shingle deterioration.
Blistering
Raised bubbles on the shingle surface caused by moisture trapped in the shingle during manufacturing or by excessive heat in poorly ventilated attics.
Boot (Pipe Boot)
A rubber or metal flashing fitted around plumbing vent pipes where they penetrate the roof. Boots deteriorate after 10-15 years and are a common source of roof leaks.
Built-Up Roofing (BUR)
A flat or low-slope roofing system made of alternating layers of bitumen and reinforcing fabrics. Common on commercial buildings.
Bundle
A package of shingles. Most architectural shingles require 3-4 bundles per square (100 sq ft).
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