Asphalt shingle
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An asphalt shingle is a type of roof shingle. They are one of the most widely used roofing covers because they are relatively inexpensive and fairly simple to install.
[edit] Types of Asphalt Shingles
Two types of asphalt shingles are used: organic and fiberglass or glass fiber. Organic shingles are generally paper (felt) saturated with asphalt to make it waterproof, then a top coating of adhesive asphalt is applied and ceramic granules are then embedded. In the case of algae-resistant shingles, a portion of the granules contain leachable copper or tin designed to inhibit moss growth and discoloration from algae on the roof.
Shingles are judged by weight per square. Organic shingles contain around 40% more asphalt per square (100 sq. ft.) than fiberglass shingles which makes them weigh more and gives them excellent durability and blow-off resistance. Shingle durability is ranked by waranteed life, ranging from 20 years to 50 years; in some cases lifetime warranties are available.
Fiberglass shingles have a base layer of glass fiber reinforcing mat. The glass fiber mat is not waterproof by itself. Fiberglass 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 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.
The older asbestos versions were very durable and hard to tear, an important property when considering wind uplift of shingles in heavy storms. Fiberglass is slowly replacing felt reinforcement in Canada and has replaced mostly all in the United States. Widespread hurricane damage in Florida during the 1990s prompted the industry to adhere to a 1700 gram tear value on finished asphalt shingles.
A newer design of fiberglass asphalt shingle, called laminated or architectural, uses two distinct layers which are bonded together. Laminate shingles are heavier, more expensive, and arguably more durable than traditional shingle designs. Laminated shingles also give a more varied, contoured visual effect to a roof surface.
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-percent slope) or greater. Asphalt shingles shall be fastened to solidly sheathed decks.
[edit] Durability
Asphalt shingles usually last longer in cooler climates than warmer ones. Thermal shock is one thing that is damaging to shingles (thermal shock is what roofing materials experience when the ambient temperature changes dramatically within a very short period of time). Another factor affecting asphalt shingle roofs is attic ventilation. Proper roof ventilation has been known to extend the service life of a roof. Shingles should not be applied during cold weather. Each shingle must seal to the layer below it to form a monolithic structure. Sun and heat to soften the underlying exposed asphalt is a requirement during the initial phase of a new roof. Staple guns should not be used on shingles because they tear into the substrate too easily. Traditional roofing nails remain the best method of applying shingles.
