Asphalt Roofing Shingles
Types of Asphalt Roofing Shingles
Two types of base materials are used to make asphalt shingles, organic and fiberglass. Both are made in a similar manner, with an asphalt-saturated base covered on one or both sides with asphalt or modified-asphalt, the exposed surface impregnated with slate, schist, quartz, vitrified brick, stone, or ceramic granules, and the under-side treated with sand, talc or mica to prevent shingles from sticking to one-another before use.
The top surface granules block ultra-violet light, which causes the shingles to deteriorate, provides some physical protection of the asphalt core, and provides color – lighter shades preferred for their heat reflectivity in sunny climates, darker in cooler ones for their asborption. Some shingles have copper or other biocides added to the surface to help prevent algae growth. Self-sealing strips are standard on the underside of shingles to provide resistance to lifting in high winds. This material is typically limestone or fly-ash-modified resins, or polymer-modified bitumen. American Society of Civil Engineers ASTM D7158 is the standard most United States residential building codes use as their wind resistance standard for most discontinuous, steep-slope roof coverings (including asphalt shingles) with the following class ratings: Class D – Passed at basic wind speeds up to and including 90 mph; Class G – Passed at basic wind speeds up to and including 120 mph; and Class H – Passed at basic wind speeds up to and including 150 mph. An additive known as styrene-butadiene-styrene (SBS), sometimes called modified or rubberized asphalt, is sometimes added to the asphalt mixture to make shingles more pliable, resistant to thermal cracking, and more resistant to damage from hail impacts. Some manufacturers use a fabric backing known as a scrim on the back side of shingles to make them more impact resistant. Most insurance companies offer discounts to homeowners for using Class 4 impact rated shingles.
Organic shingles are made with a base mat of organic materials such as waste paper, cellulose, wood fiber, or other materials. This is saturated with asphalt to make it waterproof, then a top coating of adhesive asphalt is applied, covered withd solid granules. Such shingles contain around 40% more asphalt per square (100 sq ft.) than fiberglass shingles. Their organic core leaves them more prone to fire damage, resulting in a maximum class "B" FM fire rating. They are also less brittle than fiberglass shingles in cold weather.
The early wood material-based versions were very durable and hard to tear, an important quality before self-sealing materials were added to the underside of shingles to bond them to the layer beneath. Also, some organic shingles produced before the early 1980s may contain asbestos.
Fiberglass Asphalt Roofing Shingles
Fiberglass reinforcement was devised as the replacement for asbestos in organic mat shingles. Fiberglass shingles have a base layer of glass fiber reinforcing mat made from wet, random-laid glass fibers bonded with urea-formaldehyde resin. The mat is then coated with asphalt containing mineral fillers to make it waterproof. Such shingles resist fire better than those with organic/paper mats, making them eligible for as high as a class "A" rating. Weight typically ranges from 1.8 to 2.3 pounds/square foot.
Fiberglass shingles gradually began to replace organic felt shingles, and by 1982 overtook them in use. Widespread hurricane damage in Florida during the 1990s prompted the industry to adhere to a 1700-gram tear value on finished asphalt shingles.
Per 2003 International Building Code Sections 1507.2.1 and 1507.2.2, asphalt shingles shall only be used on roof slopes of two units vertical in 12 units horizontal (17% slope) or greater. Asphalt shingles shall be fastened to solidly sheathed decks. Shallower slopes require asphalt rolled roofing, or other roofing treatment.
Architectural Asphalt Roofing Shingles
Asphalt Shingles come in two standard design options: Architectural (also known as Dimensional) Shingles, and 3-Tab Shingles. 3-Tab are essentially flat simple shingles with a uniform shape and size. They use less material and are thinner than Architectural Shingles, and are therefore lighter and lower cost for both the material and the installation. They also do not last as long or offer Manufacturer's Warranties as long as good architectural asphalt shingles. 3-Tab are still the most commonly installed in lower-value homes, such as those used as rental properties. However, they are declining in popularity in favor of the architectural style. Dimensional, or architectural shingles are thicker and stronger, vary in shape and size, and offer more aesthetic appeal; casting more distinct, random shadow lines better mimics the appearance of traditional roofing materials such as wood shake shingles. The result is a more natural, traditional look. While more expensive to install, they come with longer manufacturer's warranties, sometimes up to 50 Years - typically prorated, as virtually all asphalt shingle roofs are replaced before such an expiration could be reached. While 3-tab shingles typically need to be replaced after 15–18 years, Dimensional typically last 24–30 years.