2.3.4.5.6.Figure 3-26.-Installation of wood shingles.Use two rust-resistant nails in each shingle.Space them 3/4 inch from the edge and 1 1/2inches above the butt line of the next course.Double the first course of shingles. In allcourses, allow 1/8- to 1/4-inch space betweeneach shingle for expansion when they are wet.Offset the joints between the shingles at least 11/2 inches from the joints in the course below.In addition, space the joints in succeedingcourses so that they do not directly line up withjoints in the second course below.Where valleys are present, shingle away fromthem. Select and precut wide valley shingles.Use metal edging along the gable end to aid inguiding the water away from the sidewalls.Use care when nailing wood shingles. Drive thenails just flush with the surface. The wood inshingles is soft and can be easily crushed anddamaged under the nail heads.Wood shakes are usually available in several types,but the split-and-resawed type is the most popular. Thesawed face is used as the back face and is laid flat on theroof. The butt thickness of each shake ranges between3/4 inch and 1 1/2 inches. They are usually packed inbundles of 20 square feet with five bundles to the square.Wood shakes are applied in much the same way aswood shingles. Because shakes are much thicker (longershakes have the thicker butts), use long galvanized nails.To create a rustic appearance, lay the butts unevenly.Because shakes are longer than shingles, they havegreater exposure. Exposure distance is usually 7 1/2inches for 18-inch shakes, 10 inches for 24-inch shakes,and 13 inches for 32-inch shakes. Shakes are not smoothon both faces, and because wind-driven rain or snowmight enter, it is essential to use an underpaymentbetween each course. A layer of felt should be usedbetween each course with the bottom edge positionedabove the butt edge of the shakes a distance equal todouble the weather exposure. A 36-inch-wide strip ofthe asphalt felt is used at the cave line. Solid sheathingshould be used when wood shakes are used for roofs inareas where wind-driven snow is common.ROLL ROOFING.— Roll roofing is made of anorganic or inorganic felt saturated with an asphaltcoating and has a viscous bituminous coating. Finelyground talc or mica can be applied to both sides of thesaturated felt to produce a smooth roofing. Mineralgranules in a variety of colors are rolled into the uppersurface while the final coating is still soft. These mineralgranules protect the underlying bitumen from thedeteriorating effects of sun rays. The mineral aggregatesare nonflammable and increase the fire resistance andimprove the appearance of the underlying bitumen.Mineral-surfaced roll roofing comes in weights of 75 to90 pounds per square. Roll roofing may have onesurface completely covered with granules or have a2-inch plain-surface salvage along one side to allow forlaps.Roll roofing can be installed by either exposed orconcealed nailing. Exposed nailing is the cheapest butdoesn’t last as long. This method uses a 2-inch lap at theside and ends. It is cemented with special cement andnailed with large-headed nails. In concealed-nailinginstallations, the roll roofing is nailed along the top ofthe strip and cemented with lap cement on the bottomedge. Vertical joints in the roofing are cemented intoplace after the upper edge is nailed. This method is usedwhen maximum service life is required.Double-coverage roll roofing is produced withslightly more than half its surface covered with granules.This roofing is also known as 19-inch salvage edge. Itis applied by nailing and cementing with specialadhesives or hot asphalt. Each sheet is lapped 19 inches,blind-nailed in the lapped salvage portion, and thencemented to the sheet below. End laps are cemented intoplace.TILES.— Roofing tile was originally a thin, solidunit made by shaping moist clay in molds and drying itin the sun or in a kiln. Gradually, the term has come toinclude a variety of tile-shaped units made of clay,Portland cement, and other materials. Tile designs havecome down to us relatively unchanged from the Greeksand Remans. Roofing tiles are durable, attractive, and3-21
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