Steep Slope Roofing Systems
Asphalt shingles are composed of: a base material, either organic felt or glass-fiber mat, that provides support for the weather-resistant components and gives a shingle strength; asphalt and fillers; and surfacing material, generally in the form of mineral granules, that provides protection from impact and UV degradation and improves fire resistance.
They can be purchased in a wide variety colors and thicknesses.
Shingles may be produced in a single layer or two or more layers. The latter generally are known as laminated strip shingles, or architectural shingles, and they have a three dimensional appearance.
All shingle roof systems are installed over an underlayment. The underlayment (or "felt paper" as it is frequently called) is installed over the roof deck before the application of asphalt shingles. An underlayment performs two primary functions: it provides temporary weather protection until the asphalt shingles are installed, and it provides a secondary weatherproofing barrier if moisture infiltrates the asphalt shingles. Felt paper is typically installed in 15lb or 30lb sheets and are installed using roofing nails. An alternative underlayment is a peal n stick sheet such as Ice and Water Shield and it is fully adhered to the roofing substructure.
The warranty period available for composition shingles ranges from 20 years to a lifetime.
Wood Shakes and SHINGLES
Wood shakes and wood shingles are manufactured from western red cedar, cypress, pine and redwood trees. Shakes are split from logs and reshaped by manufacturers for commercial use. They are thicker at the butt end than shingles; generally, one or both surfaces are split to obtain a textured effect. A split and resawn shake has a split face and sawn back. A taper sawn shake has a natural taper and is sawn on both sides. Wood shingles are sawn on both sides and have an even taper and uniform thickness. When applied to shingles, the industry terms "Perfection" and "Royal" mean 18 inch and 24 inch lengths, respectively.
Cedar shakes and cedar shingles are available pressure treated with fire retardants and chemical preservatives for increased fire resistance and to prevent premature rot and decay in some climates.
All shingle roof systems are installed over an underlayment. Asphalt saturated, nonperforated organic felts are among the most common underlayments used for wood shakes and wood shingles; they commonly are designated as Type 15 and Type 30 or referred to as No. 15 and No. 30, which are reflective of a once used pound per square weight designation.
Wood roofing may be attached to a roof deck with noncorroding, galvanized steel or stainless steel nails or noncorroding metal staples. A minimum of two fasteners should be used to attach each shake or shingle. Nails should be long enough to penetrate through all layers of roofing materials and extend through the underside of the roof deck or penetrate at least 3/4 inch into wood plank or board decks.
Roofing slate is a dense, durable, naturally occurring material that is essentially nonabsorbent. Two properties of slate are cleavage and fracture. It has natural cleavage, which permits it to be easily split in one direction. Fracture, usually occurring at right angles to the cleavage, is called the grain. Roofing slate commonly is split so the length of the slate runs in the direction of the grain. The surface texture of slate after being split for commercial use derives from the characteristics of the rock from which it was quarried. Some slate splits to a smooth, practically even surface, while other yields a surface that is rough and uneven.
The color of slate is determined by its chemical and mineral composition. Because these factors differ in various regions, roofing slate can be obtained in a variety of colors. In addition, exposure to weather causes slate to change color. The degree of change varies depending on the slate. Slate exhibiting minimal color change is known as "permanent" or "unfading" slate. Slate that shows a more marked color change is known as "weathering" slate. Between unfading slate and weathering is "semi weathering" slate.
As with all of the steep slope options Slate requires an underlayment (or "felt paper" as it is frequently called) be installed over the roof deck before the application of slate. The underlayment performs two primary functions: it provides temporary weather protection until the slate is installed, and it provides a secondary weatherproofing barrier if moisture infiltrates the slate roof covering. Many slate roofs have outlived the underlayment felts over which they were installed. Therefore, an underlayment's service life should be comparable to the design service life of the slate roof covering.
Clay tile is produced by baking molded clay into tile. The density of the clay is determined by the length of time and temperature at which it is heated. Tiles may be glazed and also may have surface texture treatments applied. As a result, there are a wide variety of tile profiles, styles, finishes and colors available. In addition, there may be separate accessory tiles—matched to each field tile design—of various shapes designed for use on ridges, hips, hip intersections and gable ends. Installation methods depend on the nature of the tile being installed; that is, whether it is two piece, one piece, interlocking or flat.
Concrete tiles are made of Portland cement, sand and water in varying proportions. The material is mixed and extruded on molds under high pressure. The exposed surface of a tile may be finished with cementitious material colored with synthetic oxide additives. The tiles are cured to reach the required strength. They generally have lugs on their undersides for anchoring to batten strips. There are additional waterlocks or interlocking ribs on the longitudinal edges that impede movement and prevent water infiltration.
As with clay tile, there are a wide variety of profiles, styles, finishes and colors available. Color may be added to the surface of a tile or dispersed throughout (color through). Special texture may be added in surface treatment. Each type of tile roof system may make use of separate ridge, hip, hip intersection, gable end and finial accessory tiles of various shapes in addition to field tiles
As with all of the steep slope options tile requires an underlayment (or "felt paper" as it is frequently called) be installed over the roof deck before the application of slate. The underlayment performs two primary functions: it provides temporary weather protection until the slate is installed, and it provides a secondary weatherproofing barrier if moisture infiltrates the slate roof covering. Many tile roofs have outlived the underlayment felts over which they were installed. Therefore, an underlayment's service life should be comparable to the design service life of the tile roof covering
Metal roof systems
There are three general categories of metal roof systems used for steep-slope roofing applications: architectural metal panel, structural metal panel and metal shingle/shingle panels. Generally, architectural metal panel roof systems are watershedding and are intended for use on steep slope roofs. Structural metal panel roof systems are used on low and steep slope roofs. Structural metal panel roof systems can be used on low slope roofs because of their hydrostatic, or water barrier, characteristics.
Because architectural metal panel roof systems typically are designed to be used on steep slopes that will shed water rapidly over the metal panels' surface, the seams typically are not watertight. Many architectural metal roof systems are well suited for use on roof slopes of 3 inches per foot (14 degrees) or greater. One exception to the general slope guidelines for architectural metal panel roof systems is the traditional flat seamed, soldered or welded metal roof system, such as copper. It may be specified on slopes less than 3 inches per foot (14 degrees). Solid roof sheathing, or decking, is required for architectural metal panel roof systems, and NRCA recommends using underlayment.
Most structural metal panel roof systems are designed to resist the passage of water at laps and other joints, as sealant or anti capillary designs can be used in the seams. Structural metal panel roof systems possess strength characteristics that allow them to span supporting members.
Metal shingles and shingle panels are available in numerous varieties for use as steep-slope roof coverings. Most of the metal shingles are press-formed during the manufacturing process to provide a variety of shapes. These products can take the shape of individual or multiple asphalt, tile, slate or wood shingle configurations.
Metal roof system come in a wide variety of colors
Underlayment (or "felt paper" as it is frequently called) is installed over the roof deck before the application of a metal roof system. An underlayment performs two primary functions: it provides temporary weather protection until the metal roof system is installed, and it provides a secondary weatherproofing barrier if moisture infiltrates the metal roof panels.