An asphalt shingle is a type of wall or roof shingle that uses asphalt for waterproofing. They are one of the most widely used roofing covers in North America because they have a relatively inexpensive up-front cost and are fairly simple to install.
Two types of base materials are used to make asphalt shingles: A formerly-living organic base and fiberglass base. Both types are made in a similar manner with asphalt or modified-asphalt applied to one or both sides of the asphalt-saturated base, covered with slate, schist, quartz, vitrified brick, stone, or ceramic granules and the back side treated with sand, talc or mica to prevent the shingles from sticking to each other before use. The top surface granules block ultra-violet light which causes the shingles to deteriorate, provides some physical protection of the asphalt and gives the shingles their color. Some shingles have copper or other materials added to the surface to help prevent algae growth. Self-sealing strips are standard on shingles to help prevent the shingles from being blown off by 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 resistant to thermal cracking, as well as 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 formerly living (organic) materials such as paper (waste paper), cellulose, wood fiber, or other materials saturated with asphalt to make it waterproof, then a top coating of adhesive asphalt is applied and ceramic granules are then embedded. Organic shingles contain around 40% more asphalt per square (100 sq ft.) than fiberglass shingles. The paper-based nature of "organic" shingles leaves them more prone to fire damage, and their highest FM rating for fire is class "B". Organic shingles are less brittle than fiberglass shingles in cold weather.
The older organic (wood and paper pulp product) versions were very durable and hard to tear, an important property when considering wind uplift of shingles in heavy storms. Also, some organic shingles produced before the early 1980s may contain asbestos.
Fiberglass shingles have a base layer of glass fiber reinforcing mat. The mat is made from wet, random-laid fiberglass bonded with urea-formaldehyde resin. The mat is then coated with asphalt which contains mineral fillers and makes the fiberglass shingle waterproof. Fiberglass shingles typically obtain a class "A" fire rating as the fiberglass mat resists fire better than organic/paper mats. Fiberglass reinforcement was devised as the replacement for asbestos paper reinforcement of roofing shingles and typically ranges from 1.8 to 2.3 pounds/square foot.
Fiberglass shingles are slowly replacing organic felt shingles and by 1982 the production of fiberglass shingles overtook organic shingles. 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.
Architectural or 3-Tab
Asphalt Shingles come in two standard design options: Architectural (Dimensional) Shingles, and 3-Tab Shingles. 3-Tab are essentially flat simple shingles with a uniform shape and size. They use less material than Architectural Shingles, and are therefore lighter and lower cost for both the material and the installation. They are also thinner, and do not last as long or offer Manufacturer's Warranties as long as good Architectural Asphalt. 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 Architectural. Dimensional, or Architectural Shingles are thicker and stronger, and they offer more aesthetic appeal with their "dimensional" look with more shadow and varied shapes and sizes. While more expensive to install, they come with longer Manufacturer's Warranties, sometimes up to 50 Years. Though, it is worth noting that most Asphalt Shingles are still likely to be replaced after no longer than 24–30 years, and a long warranty such as this is often prorated. While no Asphalt Shingle is likely to last for 50 years, Dimensional Shingles will stand up better to the elements, and offer less potential for leaking (and the high costs of the damage that can come with roof leaks), typically for a longer period of time. While 3-tab shingles typically need to be replaced after 15–18 years, Dimensional typically last 24–30 years.
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