An asphalt shingle is a type of roof shingle

Roof shingle

Roof shingles are a roof covering consisting of individual overlapping elements. These elements are typically flat rectangular shapes laid in rows from the bottom edge of the roof up, with each successive higher row overlapping the joints in the row below...

. They are one of the most widely used roofing covers because they are relatively inexpensive and fairly simple to install.

Types

Two types of asphalt shingles are used: organic and fiberglass

Fiberglass

Glass fiber is a material consisting of numerous extremely fine fibers of glass.Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the invention of finer machine tooling...

or glass fiber. Organic shingles are generally paper (waste paper) saturated with asphalt

Asphalt

Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...

 to make it waterproof, then a top coating of adhesive

Adhesive

An adhesive, or glue, is a mixture in a liquid or semi-liquid state that adheres or bonds items together. Adhesives may come from either natural or synthetic sources. The types of materials that can be bonded are vast but they are especially useful for bonding thin materials...

 asphalt is applied and ceramic

Ceramic

A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...

 granules are then embedded. In the case of algae

Algae

Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

-resistant shingles, a portion of the granules contain leachable copper

Copper

Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 ceramically coated, designed to protect against discoloration from algae on the roof. This does not protect from moss

Moss

Mosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...

 growth but does slow the growth. Moss feeds on algae and any other debris on the roof. Most manufactures offer a 5- to 10-year warranty

Warranty

In business and legal transactions, a warranty is an assurance by one party to the other party that specific facts or conditions are true or will happen; the other party is permitted to rely on that assurance and seek some type of remedy if it is not true or followed.In real estate transactions, a...

 against algae growth.

Shingles are judged by warranty and ASTM test standards. Organic shingles contain around 40% more asphalt per square (100 sq ft.) than fiberglass shingles. But this extra needed asphalt makes them less environmentally friendly (despite its "organic" nickname). The paper-based nature of "organic" shingles leaves them more prone to fire damage, and their highest FM

FM Global

FM Global is a U.S.-based insurance company, with offices worldwide, that specializes in loss prevention services primarily to large corporations throughout the world in the Highly Protected Risk property insurance market sector. "FM Global" is the communicative name of the company, whereas the...

 rating for fire is class "B". Shingle durability is ranked by warranted 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 mat is made from wet, random-laid fiberglass bonded with urea

Urea

Urea or carbamide is an organic compound with the chemical formula CO2. The molecule has two —NH2 groups joined by a carbonyl functional group....

-formaldehyde

Formaldehyde

Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...

 resin

Resin

Resin in the most specific use of the term is a hydrocarbon secretion of many plants, particularly coniferous trees. Resins are valued for their chemical properties and associated uses, such as the production of varnishes, adhesives, and food glazing agents; as an important source of raw materials...

. 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

Asbestos

Asbestos is a set of six naturally occurring silicate minerals used commercially for their desirable physical properties. They all have in common their eponymous, asbestiform habit: long, thin fibrous crystals...

 paper reinforcement of roofing shingles and typically ranges from 1.8 to 2.3 pounds/square foot.

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. Fiberglass is slowly replacing felt reinforcement in Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 and has replaced mostly all in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. Widespread hurricane damage in Florida

Florida

Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

 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 with asphalt sealant. Laminated shingles are heavier, more expensive, and more durable than traditional 3-tab shingle designs. Laminated shingles also give a more varied, contoured visual effect to a roof surface.

Per 2003 International Building Code

International Building Code

The International Building Code is a model building code developed by the International Code Council . It has been adopted throughout most of the United States.-History:...

 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

Slope

In mathematics, the slope or gradient of a line describes its steepness, incline, or grade. A higher slope value indicates a steeper incline....

) or greater. Asphalt shingles shall be fastened to solidly sheathed deck

Roof Deck

The roof deck is the roofing material layer between the primary structural components and either insulative layers or weatherproofing layers in a typical roof system.-Structure:...

s.

Durability

Asphalt shingles usually last longer in cooler climates than warmer ones. Thermal shock

Thermal shock

Thermal shock is the name given to cracking as a result of rapid temperature change. Glass and ceramic objects are particularly vulnerable to this form of failure, due to their low toughness, low thermal conductivity, and high thermal expansion coefficients...

 can damage to shingles, when the ambient temperature changes dramatically within a very short period of time. Proper roof ventilation

Ventilation (architecture)

Ventilating is the process of "changing" or replacing air in any space to provide high indoor air quality...

can extend the service life of a roof. Shingles should not be applied when temperatures are under 50 degrees, as each shingle must seal to the layer below it to form a monolithic structure. The underlying exposed asphalt must be softened by sunlight and heat. A few shingle types utilize release tape which must be removed just prior to installation.

Aging and failure of asphalt shingles

Left: Example of faster asphalt shingle wear along eaves due to channeled water running down the roof. Right: Severe shrinkage resulting in tearing away of entire flaps. Water running down the roof can seep around the exposed nails into the interior space.

The protective nature of asphalt shingles primarily comes from the long-chain hydrocarbons impregnating the paper. Over time in the hot sun, the hydrocarbons soften and when rain falls the hydrocarbons are gradually washed out of the shingles and down onto the ground. Along eaves and complex rooflines more water is channeled so in these areas the loss occurs more quickly. Eventually the loss of the heavy oils causes the fibers to shrink, exposing the nail heads under the shingle flaps. The shrinkage also breaks up the surface coating of sand adhered to the surface of the paper, and eventually causes the paper to begin to tear itself apart. Once the nail heads are exposed, water running down the roof can seep into the building around the nail shank, resulting in rotting of roof building materials and causing moisture damage to ceilings and paint inside.