Frequently Asked Questions

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Steep-Slope FAQs

How many homes are topped by asphalt shingles? Why?

 

Asphalt shingles are the leading choice for residential roofing in the United States because they provide quality, durability, versatility and economy. Over 12.5 billion square feet of asphalt shingle products are manufactured annually – enough to cover more than 5 million homes every year. Four out of five homes are roofed with asphalt shingles.

Asphalt shingles offer consumers the broadest array of colors, shapes, and textures available. With an enormous range of styles, asphalt shingles can match almost every type of architectural design and achieve virtually any desired effect – and do it affordably.

What are some of the benefits of asphalt shingles?

 

  • Product Performance. Asphalt shingles perform well in extreme temperatures and in areas where wind, water, and ice are prevalent.

  • Affordability. The efficient, high-volume production and relatively low application cost of asphalt shingles provide consumers with an overall value that’s tough for other roofing materials to match, especially in terms of comparable life expectancy.

  • Low Maintenance. Asphalt shingles, when properly chosen and applied, require little or no regular upkeep, and are easily repaired if damaged.

  • Ease of Application. Asphalt shingles are considered to be the easiest of all standard roofing materials to apply. In addition, the flexibility and strength of asphalt shingles supports their application on a wide variety of roof designs.

  • Fire and Wind Resistance. Asphalt shingles are manufactured to resist external fire and flammability standards, and carry Class A, B or C fire ratings, with Class A providing the greatest fire resistance. These fire ratings are defined by nationally recognized standards and tested by independent testing agencies. In addition, many asphalt shingles carrying a "wind resistance" label indicate that they have been manufactured and tested to demonstrate acceptable resistance in high-wind locations."

How are asphalt shingles made?

In the United States, asphalt shingles are categorized as either organic-based or fiberglass-based. Organic-based asphalt shingles are manufactured with a base (also termed mat or substrate) made of various cellulose fibers, such as recycled waste paper and wood fibers. This organic base is then saturated with a specially formulated asphalt coating and surfaced with weather resistant mineral granules. Fiberglass-based asphalt shingles are manufactured with mat composed entirely of glass fibers of varying lengths and orientations. This fiberglass base is then surfaced with a specially-formulated asphalt coating, followed by weather-resistant mineral granules.

What are the different types of asphalt shingles?

 

  • Strip Shingles -- these asphalt shingles are approximately three times as long as they are wide. Manufactured in both standard and metric dimensions, strip shingles are distinguished by the number of cutouts or tabs that they have. The most common type of strip shingle is the "three-tab" shingle. Different textural and lighting/shadowing effects can be achieved with strip shingles depending on the number, shape and alignment of the cutouts.

  • Laminated Shingles -- these special shingles contain more than one layer of tabs to create extra thickness. They are also referred to as three-dimensional or architectural shingles because they create visual depth on a roof and impart a custom look. Laminated shingles continue to be a favorite among builders, roofing contractors and homebuyers.

  • Interlocking Shingles -- as the name suggests, interlocking asphalt shingles are individual shingles that mechanically fasten to each other, and are used to provide greater wind resistance. They come in various shapes and sizes providing a wide range of design possibilities.

  • Large Format Shingles --generally rectangular or hexagonal in shape, these shingles do not utilize cutouts or tabs.

How do I determine if a roof should be replaced?

 

Sooner or later, every roof needs to be replaced, usually due to the long-term effects of weathering. If a residential roof is more than 20 years old, it is a prime candidate for reroofing. To determine if you need a new roof:

  • On the ground, walk around your home with binoculars and inspect your roof for cracked, curled or missing shingles, as well as any excessive loss of the protective mineral granules. DO NOT CLIMB ON THE ROOF; walking on the roof is dangerous and can damage your roof.

  • In your attic, take a flashlight and look at the underside of the roof deck and rafters for any stains or wet spots indicating water leaks.

Asphalt shingles can often be applied directly over existing roofs without the necessity of tearing off the old roof. However, new shingles can not be properly applied over hard or brittle materials, uneven surfaces for nailing or roof decks with warped, rotted or unsound support that should first be replaced or repaired.

Some local ordinances forbid reroofing over two or more layers of shingles. If a home already has been shingled several times, it is important to first determine if the roof deck can support another layer of shingles before undertaking any re-roofing project.

What is roll roofing?

 

In addition to asphalt shingles, asphalt roll products are used for residential roofing applications (primarily for underlayments and flashings). There are four basic types of roll roofing materials, each tailored for use in certain job requirements:

  • Smooth Surfaced Roll Roofing. Also termed coated felt, this smooth-surfaced roll roofing is covered with ground talc or mica. It is used primarily as flashing to seal the roof at intersections and protrusions, and for providing extra deck protection at the roof’s eaves and valleys.

  • Saturated Felt. This asphalt-impregnated, organic-based felt is used as an underlayment between the roof deck and the roofing material. Saturated felt is produced in a variety of weights.

  • Specialty-Eaves Flashings. This self-adhering, polymer-modified bituminous sheet material is designed for special flashing applications along roof eaves and in other areas. It is used particularly in regions where ice dams and water backups are common.

  • Mineral-Surfaced Roll Roofing. This type of roll roofing is used alone as a primary roof covering, most frequently on small or secondary-use buildings such as supply buildings, barns, garden sheds, etc. The top surface of the roll is imbedded with mineral granules.

What are some steep-slope roofing terms?

Architectural Shingles: (See Laminated Shingles)
Asphalt: A bituminous waterproofing agent applied to roofing materials during manufacture. 
Deck: The structural surface to which the roofing or waterproofing system (including insulation) is applied. 
Flashing: Pieces of metal or roll roofing used to prevent seepage of water into a building around any intersection or projection in a roof, such as vent pipes, chimneys, adjoining walls, dormers and valleys.
Granules: Ceramic-coated colored crushed rock that is applied to the exposed surface of asphalt roofing products. 
Hip: The inclined external angle formed by the intersection of two sloping roof planes. Runs from the ridge to the eaves.
Incline: The slope of a roof expressed either in percent or in the number of vertical units of rise per horizontal unit of run. Also referred to as slope. 
Interlocking Shingles: Individual shingles that fasten together mechanically and provide greater wind resistance. 
Laminated Shingles: These shingles have more than one layer of tabs to create extra thickness. They are often referred to as three-dimensional or architectural shingles because they create visual depth on a roof and impart a custom look.
Large Format Shingles: Generally rectangular or hexagonal in shape, these shingles do not have cutouts or tabs.
Membrane: A roof covering or waterproofing layer whose primary function is the exclusion of water.
Pitch: The degree of roof incline or slope expressed as the ratio of the rise, in feet, to the span, in feet.
Re-covering: The process of covering an existing roofing system with a new roofing system. 
Re-roofing: The practice of removing an existing roofing system and replacing it with a new roofing system. 
Ridge: The uppermost, horizontal external angle formed by the intersection of two sloping roof planes.
Roll Roofing: Asphalt roofing products manufactured in roll form, either smooth- or mineral-surfaced. 
Saturated Felt: An asphalt-impregnated felt used as an underlayment between the deck and the roofing material. 
Self-Adhered Eave and Flashing Membrane: A self-adhering water-proofing shingle underlayment designed to protect against water infiltration due to ice dams or wind driven rain.
Strip Shingles: Manufactured in both standard and metric dimensions, these asphalt shingles are approximately three times as long as they are wide, and are distinguished by the number of cutouts or tabs that they have. The most common are three tab.
Square: A unit of roof measure covering 100 square feet. 
Thermal Insulation: A material applied to reduce the flow of heat.
Three-Dimensional Shingles: (See Laminated Shingles)
Underlayment: Asphalt saturated felt used beneath roofing to provide additional protection for the deck.
Valley: The internal angle formed by the intersection of two sloping roof planes. 
Vapor Retarder: A material designed to impede the passage of water vapor into the roofing system.

Low-Slope FAQs

What are the major low-slope roofing systems?

The two broad categories of asphalt roofing systems for commercial, industrial and institutional buildings are Built-Up Roofing (BUR) and Modified Bitumen Systems (MBS).

What is Built-Up Roofing (BUR)?

 

Built-up Roofing (or BUR) is the most popular choice of roofing used on commercial, industrial and institutional buildings. BUR is used on flat or low-sloped roofs and consists of multiple layers of bitumen and ply sheets. Components of a BUR system include the roof deck, a vapor retarder, insulation, membrane and surfacing material. The components are assembled at the job site to actually form the built-up roof. At the heart of this roofing system is the roofing membrane, which consists of roofing bitumen and multiple reinforcing plies of roofing felt.

Roofing bitumen is the primary adhesion/waterproofing agent used between roofing plies. Bitumen arrives at the job site in solid form, but is heated and applied as a liquid. Roofing bitumens may be either a product of petroleum refining (asphalts) or a product of the coal-cooking process (coal tar pitch).

Multiple reinforcing “plies” are asphalt-coated roofing sheets or felts installed in three or more layers to strengthen and stabilize the BUR membrane. These multiple reinforcing felts also make the membrane more pliable and resilient, protect the bitumen from water degradation, and serve as a fire-retarding element in the membrane system.

BUR roofing membranes can be protected from solar radiation by embedding gravel in the bitumen, applying a surface coating or applying a granular-surfaced “cap” sheet. Light-colored surfacing materials can be used to reflect heat from the building. In addition, surfacing agents can provide additional fire protection.

How is BUR applied for maximum performance?

 

It's critical to get secure bonding of the roofing felts (plies) using bitumen. To achieve this bond the roofing contractor applies thin, uniform moppings of bitumen. This waterproofs the system and ensures proper adhesion for fusing the membrane system together. The temperature of the bitumen is critical. By heating it to the proper temperature the roofing contractor gets the right viscosity for proper mopping. The contractor heats the bitumen to its EVT or Equiviscous Temperature, the temperature at which it can be most effectively mopped into uniform layers. Each batch of bitumen should be labeled by the supplier with its EVT.

Once felts are rolled into place on the heated bitumen applicators pull brooms or squeegees over the felt or use some other method to make sure that its embedded in the bitumen.

The strength of the membrane depends on the type of felt used, the number of plies, overall ply construction, and the lapping of the overlaying felts. Typically, membrane ply construction is defined by headlap, endlap, and sidelap. Headlap is the distance of the overlap that exists between the lowermost and the uppermost plies of the shingled portion of the roof membrane when measured perpendicular to the long dimension of the membrane. Endlap is the overlap distance that is measured from where one roll of felt ends to where another begins. Sidelap is the overlap distance along the length of the felt where one roll of felt overlaps the adjacent overlying felt.

The application of Built-Up Roofing systems is detailed work, but the professional who pays particular attention to those details such as curbs, walls, flashings or other projections that interrupt the membrane, achieves a quality, efficient, long-lasting product for the building owner.

ARMA offers many sources of information to enable the roofing professional to do just that.