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An asphalt shingle is a type of wall or roof shingle that uses asphalt for waterproofing. It is one of the most widely used roofing covers in North America because it has a relatively inexpensive up-front cost and is fairly simple to install. [1]
Asphalt shingles are an American invention by Henry Reynolds of Grand Rapids, Michigan. [2] They were first used in 1903, in general use in parts of the United States by 1911 and by 1939 11 million squares (100 million square meters) of shingles were being produced. [3] A U.S. National Board of Fire Underwriters campaign to eliminate the use of wood shingles on roofs was a contributing factor in the growth in popularity of asphalt shingles during the 1920s. [4] The forerunner of these shingles was first developed in 1893 and called asphalt prepared roofing, which was similar to asphalt roll roofing without the surface granules. [5] In 1897 slate granules were added to the surface to make the material more durable. Types of granules tested have included mica, oyster shells, slate, dolomite, fly-ash, silica and clay. In 1901 this material was first cut into strips for use as one-tab and multi-tab shingles.
All shingles were organic at first with the base material, called felt, being primarily cotton rag until the 1920s when cotton rag became more expensive and alternative materials were used. Other organic materials used as the felt included wool, jute or manila, and wood pulp. [6] In 1926 the Asphalt Shingle and Research Institute with the National Bureau of Standards tested 22 types of experimental felts and found no significant differences in performance. In the 1950s self-sealing and manually applied adhesives began to be used to help prevent wind damage to shingle roofs. The design standard was for the self-sealing strips of adhesive to be fully adhered after sixteen hours at 140 °F (60 °C). Also in the 1950s testing on the use of 3⁄4-inch (19 mm) staples rather than roofing nails was carried out showing they could perform as well as nails but with six staples compared with four nails. [3] In 1960 fiberglass mat bases were introduced with limited success; the lighter, more flexible fiberglass shingles proved to be more susceptible to wind damage particularly at freezing temperatures. Later generations of shingles constructed using fiberglass in place of asbestos provided acceptable durability and fireproofing. [7] Also in the 1960s research into hail damage found that it occurs when hail reaches a size larger than 1.5 inches (38 mm).
The Asphalt Roofing Manufacturers Association (ARMA) formed the High Wind Task Force in 1990 to continue research to improve shingle wind resistance. [8] In 1996, a partnership between members of the U.S. property insurance industry, the Institute of Business and Home Safety, and the Underwriter's Laboratory (UL) was established to create an impact resistance classification system for roofing materials. The system, known as UL 2218, established a national standard for impact resistance. Subsequently, insurers offered discounted premiums for policies on structures using shingles that carried the highest impact classification (class 4). In 1998, Texas Insurance Commissioner Elton Bomer mandated that Texas provide premium discounts to policyholders that installed class 4 roofs. [9]
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, [6] 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 absorption. 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 (140 km/h); Class G – Passed at basic wind speeds up to and including 120 mph (190 km/h); and Class H – Passed at basic wind speeds up to and including 150 mph (240 km/h). 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.[ citation needed ]
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 with solid granules. Such shingles contain around 40% more asphalt per unit area 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.
Almost all major asphalt shingle manufacturers stopped production of organic shingles during the mid-to-late 2000's, with Building Products of Canada being the last manufacturer to make organic shingles, finally ceasing production in 2011. [10]
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. Area density typically ranges from 1.8 to 2.3 pounds per square foot (8.8–11.2 kg/m2).
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[ citation needed ].
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.
Asphalt shingles come in two standard design options: architectural (also known as dimensional) shingles, and three-tab shingles. Three-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. Three-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. [7] 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 three-tab shingles typically need to be replaced after 15–18 years, Dimensional typically last 24–30 years.
Asphalt shingles have varying qualities which help them survive wind, hail, or fire damage and discoloration.
Shingles tend to last longer where the weather stays consistent, either consistently warm, or consistently cool. Thermal shock can damage shingles, when the ambient temperature changes dramatically within a very short period of time.[ citation needed ] "Experiments...have noted that the greatest cause of asphalt shingle aging is thermal loading." [5] Over time the asphalt becomes oxidized and becomes brittle. Roof orientation and ventilation can extend the service life of a roof by reducing temperatures. [13] Shingles should not be applied when temperatures are below 10 °C (50 °F), 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 to form a proper bond.
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| 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[ citation needed ]. 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.
Cycles of wet and dry environmental conditions, as well as organic growths such as algae and foliose lichen and woody debris which remains on the shingles, will cause premature deterioration through both chemical and physical processes. [4] [14] Performed regularly, physical removal of debris, and physical or chemical removal of organic growth (for example, using a copper sulfate, zinc chloride, or other solution carefully applied and thoroughly rinsed), can prolong the life of asphalt roofing materials. [4] Algae and moss growth may be prevented through installation of zinc or copper strips or wire at the ridge and every four to six feet down the roof; black algae growth can be removed with a bleach solution. [4] [15]
According to a 2007 study conducted for the United States Environmental Protection Agency (EPA), approximately 11 million short tons (10.0 Mt) of asphalt shingle waste is generated each year in the United States, with the most common disposal method being landfilling. [16] Waste asphalt shingles, however, can be recycled.
Reclaimed asphalt shingles (RAS) can be broken down and incorporated into asphalt concrete mixtures, which are used to form pavements and road surfaces. RAS are an attractive component in recycled asphalt mixes, primarily due to their relatively high content of asphalt cement, [17] which acts as the binding element in asphalt concrete. [18]
There are two forms of RAS: post-manufacturer shingles that are reclaimed from factory waste, and post-consumer shingles that are reclaimed at the end of their service life (also referred to as “tear-offs”). [19] The majority of asphalt shingle waste is post-consumer. [16] Post-consumer RAS have fewer appealing properties for recycling, primarily because the asphalt cement component in shingles naturally hardens during its service life, resulting in higher stiffness, melting point, and susceptibility to fatigue cracking. [17] [19] Post-consumer RAS also require additional processing, such as the removal of nails and other metal waste through the use of a magnetic sieve. [19]
Recycled asphalt mixtures may contain post-manufacture and/or post-consumer RAS, provided that the quality of the asphalt cement binder is accessed and accounted for. Aged binders are typically combined with soft virgin asphalt binder and/or rejuvenating additives to produce a binder that is workable and resistant to fatigue cracking. [17] [19] Standard practice for accessing the binder quality in RAS and blending it with virgin binder has been established by The American Association of State Highway and Transportation Officials (AASHTO). [20] When RAS binder is combined with low-grade virgin binder, it has been demonstrated to provide some beneficial properties, such as increased resistance to rutting. [16] [17]
In 2019, an estimated 1.1 million tons of RAS were accepted by asphalt plants. Of those accepted, approximately 423 thousand tons were pre-processed, 334 thousand tons were unprocessed post-manufacturer shingles, and 277 thousand tons were unprocessed post-consumer shingles. [21]
The use of RAS in recycled asphalt mixes is entirely prohibited in 10 states, and the majority of states that allow the use of RAS restrict it to certain sectors and pavement types. [21] The primary reason restrictions on the use of RAS exist is the rare presence of asbestos in asphalt shingles manufactured before the early 1980s. [16] Although the lifespan of a typical asphalt shingled roof is approximately 25 years, [19] concerns remain due to the practice of layering newly installed shingles on top of old ones. [16]
In addition to shingles, asbestos has also been found present in felt paper, roll roofing, roof paints/coatings, caulking, and mastic, all of which may be present in the post-consumer shingle waste accepted by asphalt plants. [16] Still, testing has demonstrated the percentage of asbestos-containing post-consumer shingles to be low. A 2007 survey of over 27,000 samples tested at 9 different facilities detected asbestos in less than 1.6% of samples. [16]
The National Asphalt Pavement Association continues to recommend that all post-consumer RAS be inspected for asbestos and that all recycling operations have an asbestos management plan in place. [22]
Asphalt also naturally contains polycyclic aromatic hydrocarbons (PAHs) which may leach out of RAS stockpiles or be emitted when RAS are heated. [16] Some PAHs are carcinogenic and may put workers at risk. The recycling of RAS may lead to PAH emissions, however, there is no evidence to show that PAH emissions are lower when virgin asphalt is used in place of RAS. [16]
A roof is the top covering of a building, including all materials and constructions necessary to support it on the walls of the building or on uprights, providing protection against rain, snow, sunlight, extremes of temperature, and wind. A roof is part of the building envelope.
Asphalt concrete is a composite material commonly used to surface roads, parking lots, airports, and the core of embankment dams. Asphalt mixtures have been used in pavement construction since the beginning of the twentieth century. It consists of mineral aggregate bound together with bitumen, laid in layers, and compacted.
Owens Corning is an American company that develops and produces insulation, roofing, and fiberglass composites and related materials and products. It is the world's largest manufacturer of fiberglass composites. It was formed in 1935 as a partnership between two major American glassworks, Corning Glass Works and Owens-Illinois. The company employs approximately 19,000 people around the world. Owens Corning has been a Fortune 500 company every year since the list was created in 1955. The Pink Panther acts as the company's mascot and appears in most of their advertisements.
Tar paper is a heavy-duty paper used in construction. Tar paper is made by impregnating paper with tar, producing a waterproof material useful for roof construction. Tar paper is similar to roofing felt, historically a felt-like fabric made from recycled rags impregnated with melted asphalt, and today evolving into a more complex underlayment of synthetic mesh or fiberglass strands waterproofed by synthetically enhanced asphalt.
A flat roof is a roof which is almost level in contrast to the many types of sloped roofs. The slope of a roof is properly known as its pitch and flat roofs have up to approximately 10°. Flat roofs are an ancient form mostly used in arid climates and allow the roof space to be used as a living space or a living roof. Flat roofs, or "low-slope" roofs, are also commonly found on commercial buildings throughout the world. The U.S.-based National Roofing Contractors Association defines a low-slope roof as having a slope of 3 in 12 (1:4) or less.
Roof shingles are a roof covering consisting of individual overlapping elements. These elements are typically flat, rectangular shapes laid in courses from the bottom edge of the roof up, with each successive course overlapping the joints below. Shingles are held by the roof rafters and are made of various materials such as wood, slate, flagstone, metal, plastic, and composite materials such as fibre cement and asphalt shingles. Ceramic roof tiles, which still dominate in Europe and some parts of Asia, are still usually called tiles. Roof shingles may deteriorate faster and need to repel more water than wall shingles. They are a very common roofing material in the United States.
A metal roof is a roofing system featuring metal pieces or tiles exhibiting corrosion resistance, impermeability to water, and long life. It is a component of the building envelope. The metal pieces may be a covering on a structural, non-waterproof roof, or they could be self-supporting sheets.
Solar shingles, also called photovoltaic shingles, are solar panels designed to look like and function as conventional roofing materials, such as asphalt shingle or slate, while also producing electricity. Solar shingles are a type of solar energy solution known as building-integrated photovoltaics (BIPV).
A roof coating is a monolithic, fully adhered, fluid applied roofing membrane. Many roof coatings are elastomeric, that is, they have elastic properties that allow them to stretch and return to their original shape without damage.
GAF is an American manufacturing company based in Parsippany, New Jersey, that has roots dating back to the late 19th century. The GAF acronym stands for General Aniline & Film. The company has historically been primarily focused on manufacturing of roofing materials for residential and commercial applications. At one time GAF was also active in manufacturing photographic film as well as cameras and projectors, and was the manufacturer of the View-Master, the famous line of 3D transparencies, viewers and projectors. Briefly in the 1970s, it was the official film of Disneyland and Walt Disney World, and at this time actor Henry Fonda served as the company's spokesman in several television commercials, including one that featured Jodie Foster in her first acting role. John Altmeyer is the CEO of GAF, an operating subsidiary of Standard Industries.
Building insulation materials are the building materials that form the thermal envelope of a building or otherwise reduce heat transfer.
Bituminous waterproofing systems are designed to protect residential and commercial buildings. Bitumen is a material made up of organic liquids that are highly sticky, viscous, and waterproof. Systems incorporating bituminous-based substrates are sometimes used to construct roofs, in the form of "roofing felt" or "roll roofing" products.
Gloeocapsa magma is a species of bacteria in the gloeocapsa genus of cyanobacteria, an ancient line of photosynthesizing bacteria, which photolyze water generating oxygen gas. Ancient cyanobacteria were ancestral to the chloroplasts of all plants on earth. Gloeocapsa magma may resemble "algae" in that they are green, but in fact cyanobacteria are bacteria whereas algae are single-celled eukaryotes that are closely related to plants.
Asphalt roll roofing or membrane is a roofing material commonly used for buildings that feature a low sloped roof pitch in North America. The material is based on the same materials used in asphalt shingles; an organic felt or fiberglass mat, saturated with asphalt, and faced with granular stone aggregate.
CertainTeed is a North American manufacturer of building materials for both commercial and residential construction and is a wholly owned subsidiary of Saint-Gobain SA, based in Paris.
Roof cleaning is the process of removing algae, mold, mildew, lichen and moss from roofs. Also cleaning oxidation on metal roofs. Cleaning can extend the duration of a roof's ability to function. Algae and other types of build-up often form on the north and west parts of roofs that are shaded or receive less sun, and can reduce a roof's life expectancy. The presence of soot, dirt, or biomass can affect how much sunlight is absorbed by a roof and thus the amount of heat a building absorbs.
Liquid roofing is the process of waterproofing a roof by the application of a hydrophobic liquid roof coating. It can be applied to most roof styles, including flat, pitched, and domed roofs.
Copper has earned a respected place in the related fields of architecture, building construction, and interior design. From cathedrals to castles and from homes to offices, copper is used for a variety of architectural elements, including roofs, flashings, gutters, downspouts, domes, spires, vaults, wall cladding, and building expansion joints.
Rubber shingle roofs are a roof system made from recycled rubber typically EPDM or TPO rubber. The rubber shingle can emulate shake or slate in appearance.
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