Presentation on theme: "Unit 55 Roof Finish Roof Overhangs and Cornices • Open Cornices • Closed Cornices • Cornice Soffit Systems • Covering Roofs • Asphalt Shingles • Wood Shingles."— Presentation transcript:
1Unit 55Roof FinishRoof Overhangs and Cornices • Open Cornices • Closed Cornices • Cornice Soffit Systems • Covering Roofs • Asphalt Shingles • Wood Shingles and Shakes • Tile Roofing • Metal Roof Covering • Built-up Roof Covering
2Finish fascia boards are nailed to a fascia backer or directly to the roof rafter tails. In open cornice construction, the undersides of the rafters and roof sheathing are exposed. A 1″ or 2″ thick fascia board is usually nailed to the tail ends of the rafters. See Figure 55‑1. Most spaces between rafters are blocked; some spaces are left open (and screened) to allow attic ventilation.
3In open cornice construction, the frieze board is cut between the rafters and molding is nailed over the frieze board.Usually a frieze board is nailed to the wall below the rafters. The frieze board is a horizontal piece that provides a watertight connection between the top of the siding and the cornice. In some cases, the frieze board is notched between the rafters and bed molding is nailed over it. See Figure 55‑2.
4For a flat box cornice with a plywood soffit, the soffit is nailed to the upper edge of the frieze board and to the underside of the lookouts. Note the metal soffit vent installed in the soffit for ventilation.A flat box cornice requires framing pieces called lookouts that are toenailed to the wall and facenailed to the ends of the rafters. Lookouts provide a nailing base for the soffit, which is the material that is fastened to the underside of the cornice. A typical flat box cornice is shown in Figure 55‑3.
5Lookouts are not required for a sloped box cornice Lookouts are not required for a sloped box cornice. The soffit is nailed directly to the underside of the rafters. Note the soffit angle when compared to the flat box cornice shown in Figure 55-3.For a sloped box cornice, the soffit material is nailed directly to the underside of the rafters. See Figure 55‑4. Sloped box cornice designs are common on houses with wide overhangs.
6A flat box cornice requires a cornice return at the corner intersection of the gable end overhang and eaves soffits.The construction of a gable end overhang, also known as the rake section, is explained earlier in this textbook. The basic trim pieces in the gable end overhang are the fascia board and soffit material. Figure 55‑5 shows the finished gable end overhang for a flat box cornice.
7A sloped box cornice does not require a cornice return at the gable end overhang. Figure 55‑6 shows the finished gable end overhang for a sloped box cornice.
8Vinyl cornice soffits and trim finish the overhang of this building Vinyl cornice soffits and trim finish the overhang of this building. Note the vent openings in the soffit panels of the upper level.Plywood, hardboard, OSB, and fiberboard panels may be used for cornice soffits. For a more rustic effect, different types of siding patterns may be applied. Cornice trim and soffit systems are also available in aluminum and vinyl, in a variety of colors and designs. See Figure 55‑7. Manufacturer instructions should be carefully followed when installing aluminum and vinyl systems.
9Gutters and downspouts drain water from a roof. Gutters fastened to fascia boards collect water runoff from the roof and channel the water to downspouts. Gutters and downspouts are made of aluminum, plastic, or galvanized steel. Sectional gutters and downspouts are commonly installed on residential structures. See Figure Seamless aluminum gutters generally are installed on light commercial and commercial buildings.
10Shingles and shakes must be properly lapped to ensure the roof is watertight. Wood shingles and shakes are produced from cedar logs. Wood shingles are cut from the logs. Shakes are similar to wood shingles but are split rather than sawn from logs. Shakes are applied when a more rustic effect is desired. Regardless of the shingle material, the following key terms are related to shingle application:• Shingle width: total distance across the top of either a strip or individual shingle. See Figure 55-9.• Toplap: distance that one shingle overlaps a shingle in the course (row) below it• Sidelap: distance that one shingle overlaps a shingle next to it in the same course• Headlap: distance that one shingle overlaps a shingle two courses below it. Headlap is measured from the bottom edge of an overlapping shingle to the nearest top edge of an overlapped shingle• Exposure: distance between the exposed edges of overlapping shingles
11In cold climates, eaves flashing is installed along the roof eaves and extends 12″ to 24″ inside the building wall line.Eaves may be flashed using asphalt-saturated felt or an ice and water guard membrane. A strip of 50-lb asphalt-saturated felt is applied over the regular layer of underlayment at the roof overhang. See Figure Flashing for the eaves should extend 12″ to 24″ inside the building. A drip edge at the top of the fascia is a metal piece that protects the edges of the roof deck and also helps to prevent leakage.
12The adhesive ice and water guard membrane is applied directly to the roof sheathing. Ice and water guards are installed along eaves and rake edges, in valleys, and on low-sloping roofs. Ice and water guard is applied directly to the roof sheathing and then rolled to ensure maximum adhesion and contact. See Figure Side laps should be a minimum of 3 1/2″, while end laps should be a minimum of 6″. Always work from the low point of a roof to its high point. Apply ice and water dam membranes in valleys prior to applying the membrane to the eaves. When applying the membrane in a valley, start at the bottom and work toward the top of the roof and roll the membrane from the center outward. When applying the membrane for a ridge, center the membrane over the peak and roll from the center outward in both directions. When the underlayment is installed, the release paper on the upper side of the membrane is removed, and the underlayment is positioned over it and rolled to provide proper adhesion. Always refer to manufacturer installation instructions for ice and water guard.
13A 2″ toplap and 4″ sidelap are required for shingle underlayment. Underlayment is always used under asphalt and fiberglass shingles, but is not always required under wood shingles and shakes. Asphalt‑saturated felt (tar paper) is used for underlayment. Underlayment should be applied over the entire roof surface as soon as the sheathing installation has been completed. A 2″ toplap is required at horizontal joints and a 4″ sidelap is required at end joints of the underlayment. See Figure 55‑12.
14Asphalt strip shingles are available in many designs Asphalt strip shingles are available in many designs. Seal-down adhesive tabs help to prevent wind damage to the shingles.Asphalt strip shingles are available in several different designs. See Figure 55‑13.
15Individual asphalt shingles are primarily used for restoration work. Strip shingles are commonly used for new construction. Individual shingles are primarily used for restoration work. See Figure 55‑14.
16Open valley or closed valley flashing may be used on asphalt‑shingled roofs. An asphalt‑shingle roof requires underlayment and usually some type of flashing. Open valley or closed valley flashing may be used. See Figure 55‑15. In open valley flashing, 18″ strips of mineral‑surfaced roofing material are placed face down at the valley. A second piece (36″ strip) is cemented face up over the first strip. The shingles are applied over the flashing. Shingle edges along the valley should be marked and trimmed parallel to the valley. To avoid penetrating the flashing, shingles should not be cut with a utility knife while they are laying in position.
17Metal stepped flashing is necessary where a joint occurs between a pitched roof and vertical wall. Flashing is required where a pitched roof meets a vertical wall, Figure 55‑16. Metal stepped flashing extends 3″ under the shingles and at least 4″ vertically on the wall. The flashing must overlap a minimum of 2″.
18Flashing is required where stacks project above the roof. Flashing must also be installed around roof projections such as ventilation vent pipes. One method of installing flashing around roof projections is shown in Figure 55‑17.
19Smooth, annular, or screw-shank nails are used to fasten asphalt shingles to roof sheathing. Special noncorrosive, hot‑dipped galvanized steel or aluminum nails are manufactured for asphalt shingles. See Figure 5518. These nails have flat heads 3/8″ to 7/16″ in diameter and sharp points. Staples are also commonly used to fasten asphalt shingles. Pneumatic nailers and staplers are commonly used to apply underlayment and asphalt shingles.
20Drip edges, underlayment, and eaves flashing must be installed prior to installing asphalt strip shingles. In this example, three‑tab strip shingles are used.Figure 55‑19 shows a procedure for laying down asphalt strip shingles. A starter strip is placed beneath the first course of shingles. The first course starts with a full shingle. Joints between subsequent courses must be staggered to provide a tight seal. To stagger the shingle cutouts on the next course, the first tab of the first shingle must be cut. For example, the first shingle of the second course is 30″ wide when the first tab (6″) is cut off (36″ – 6″ = 30″). An additional 6″ is cut off of the first shingle of the next course, resulting in a width of 24″ (36″ – 12″ = 24″). When the width of the first shingle of a course has been reduced to 6″, the next course begins with a full shingle.
21The Boston method may be used for finishing the ridge and hips of an asphalt shingle roof. A common procedure for finishing off the ridge and hips is the Boston method. See Figure 55‑20. In this method, shingles specially formed for the ridge and hips are overlapped with a 5″ exposure. Nails are driven into the areas of the shingles covered by the overlapping shingle.
22Shingles have a smoother finish than shakes and are tapered from the butt to the concealed end. Shingles have a smoother finish than shakes. See Figure 55‑21. They are sawn from cedar blocks by a shingle‑cutting machine. Most wood shingles are produced in random widths ranging from 3″ to 14″ and in standard lengths of 16″, 18″, and 24″. Wood shingles are tapered to be thicker at the exposed butt end than at the concealed end.
23Spaced sheathing is commonly used with wood shake or shingle roofs to provide air circulation beneath the roof. Note that solid sheathing is installed over the eaves.Spaced or solid sheathing may be used as a base for nailing shingles and shakes. Spaced sheathing, except over the eaves, is recommended in most climates. See Figure 55‑22. Wood shingles and shakes tend to absorb rainwater. For this reason, air circulation underneath the shakes or shingles prevents uneven drying, which can eventually cause splits to develop.
24When nailing shingles or shakes, drive the nails until heads rest on the surface. If nails are driven into the surface, they will have less holding power. Use only two nails to a shake, placed 3/4″ from each edge and 1 1/2″ above the exposure line. Hot‑dipped, zinc‑coated nails are recommended when applying wood shingles. Aluminum and stainless steel nails are also acceptable.Hot-dipped, zinc‑coated nails are recommended for wood shingles and shakes. Aluminum and stainless steel nails are also acceptable. The nails must be long enough to pass through the shingle or shake and penetrate the sheathing at least 1/2″. A proper nailing procedure is shown in Figure 55‑23. The nail heads should rest on the surface. If the nail is driven further, it will have less holding power. Two nails are used per shingle, each 3/4″ from the edge and approximately 1 1/2″ above the exposure line.
25Greater shingle exposure is allowed for roofs with steeper slopes. The recommended exposure for wood shingles depends on the size of the shingle and the roof pitch. See Figure 55‑24.
26The first course of wood shingles should extend 1″ to 1 1/2″ beyond the eaves and 1″ beyond the rake edge of the gable.A procedure for installing wood shingles is shown in Figure 55‑25.
27Since wood shakes have rough and uneven surfaces, underlayment must be placed between each course. The rough and uneven surfaces of shakes increase the possibility of infiltration by winddriven rain and snow. For this reason, it is necessary to place a strip of underlayment between each course as the shakes are being applied. See Figure 55‑26. A 36″ wide strip of 15-lb (minimum) asphalt‑saturated felt is laid over the eave line. The bottom course of shakes is doubled. After each course of shakes, an 18″ wide strip of 15‑lb felt is placed over the top portion of the shake, extending onto the sheathing. The bottom edge of the felt placed on top of the shake is positioned from the butt a distance equal to twice the exposure of the shake. To allow for possible expansion, the shakes are spaced about 1/2″ apart and joints between the shakes are offset at least 1 1/2″ from adjacent courses.
28Hip sections of a roof are finished off with a hip cap. Hip sections of the roof are finished with a hip cap. See Figure 55‑27.
29When finishing a hip roof, shingles may be overlapped at the hip and flashing is installed in valleys.A strip of 15-lb asphalt-saturated felt, at least 8″ wide, must first be applied, and the starter course area of the hip cap is doubled. See Figure 55‑28. The joints between the shakes are beveled. The directions of the bevels are alternated with each course.
30Ridge and hip caps are also available as factory‑manufactured units. The ridge of a roof is finished off with a ridge cap, which is similar to a hip cap. See Figure 55‑29. The general procedure for placing a ridge cap is the same as for placing a hip cap.
31The open valley method is considered the most practical for finishing a valley. The potential for roof leaks occurs in areas where water is channeled for running off the roof, such as valleys between intersecting roofs. The open valley method is considered the most practical method of finishing a valley. See Figure 55‑30. The first step is to apply 15‑lb felt directly over the sheathing. Sheets of metal valley flashing at least 24″ wide, and with a 4″ to 6″ headlap, are then nailed down. The metal flashing should be 26‑ga or heavier galvanized iron. Shingles or shakes placed in the valley should be fitted so they run parallel to the valley and form a 6″ gutter.
32Flashing and counterflashing must be placed around a chimney on a wood shake roof. Other areas vulnerable to leakage are where a roof butts up against a vertical wall or around a chimney. Base flashing and counterflashing should be installed to prevent leakage. The bottom leg of the L-shaped base flashing rests on the roof and extends 6″ under the shingles. The counterflashing laps a minimum of 3″ over the base flashing. When flashing a brick chimney, the upper edge of the counterflashing is inserted at least 3/4″ into a mortar joint. Caulking is placed between the counterflashing and the chimney. See Figure
33Tile roofing provides an attractive and fireproof finish roof covering. Tile is one of the oldest types of finish covering used on pitched roofs. Tile roofing has grown increasingly popular because of its fireproofing qualities. See Figure 55‑32. Clay or concrete tile roofing is available in a variety of styles. Clay tile is manufactured by baking plates of molded clay into tile. Clay tile is lighter than concrete tile; however, concrete tile is more durable and is used more often than clay tile. Concrete tile is composed of portland cement, sand, and water.
34Tile roofing is available in a variety of field tiles and accessories. Field tile is generally classified as flat tile or roll tile. Flat tile is flat in cross section. Roll tile is curved in cross section. Accessory tiles are specially designed tiles used for different intersecting points on a roof. See Figure
35Battens are laid out to provide proper headlap for tiles. The line snapped for the upper edge of the first batten measured from the eaves is 15″ to allow for a 1″ tile overhang past the eaves. To determine the number of courses required, the distance between the chalk lines is measured and divided by 13. The exact spacing of the battens is then found by dividing the number of required courses into the distance between the top and bottom chalk lines. See Figure 55‑34.
36Metal flashing is placed in all roof areas where leaks may occur. Pan flashing is used where tiles butt against a vertical wall. Counterflashing is also recommended. Flashing placed around flues and vents is copper or other approved material that can be formed to follow the shape of the tile. See Figure 55‑35. The sides of chimneys and skylights are flashed in the same manner as straight walls. The top and bottom areas require flexible flashing material.
37Metal shingles are textured to provide the appearance of wood shakes or shingles. Metal shingles are made of aluminum or galvanized steel and are available in many solid colors as well as designs that give the appearance of wood shingles or shakes. See Figure
38Battens may be installed beneath metal shingle panels. Metal shingles may be applied individually or in panels. Battens should be installed when installing metal shingles. See Figure Metal shingle panels may have prefabricated battens attached to the backs of the panels.
39Standing-seam metal roofs provide excellent water drainage. Roll-formed panels are manufactured from aluminum, copper, zinc, and galvanized steel. Galvanized steel is the most common panel material. The panels can be preformed and/or textured to provide the panels with the appearance of shingles or tiles. Standing-seam pitched metal roofs provide good drainage for rainwater and melting snow. See Figure
40Standing-seam roll-formed panels are secured in place with clips concealed inside the seams. A factory-applied sealant inside the seam produces a watertight connection when the seams are properly installed.Standing-seam roll-formed panels are secured in place using clips that are concealed inside the seams. The clips are attached to the roof sheathing using lag bolts. While securing the roof in place, the clips also allow the panels to expand and contract with temperature changes, reducing the chance of roof leakage. See Figure
41When applying a built‑up roof, each felt layer is hot‑mopped When applying a built‑up roof, each felt layer is hot‑mopped. The final surface is covered with gravel embedded in asphalt or tar.A built‑up roof covering consists of three, four, or five individual layers of roofing felt. Built-up roofs are usually used on flat decks. Each layer is mopped down with hot tar or asphalt. The final layer is coated with gravel, which is embedded in the tar or asphalt. See Figure 55‑40.
42Built-up roof coverings are commonly used with flat roof decks constructed with parapets. Flashing, counterflashing, and asphalt-saturated felt are installed around the edges of the roof deck and other roof projections to provide a watertight seal.Built-up roofs are also used with flat roof decks constructed with parapets. Parapets are low walls along the edges of a roof. Flashing and counterflashing are installed along the edges of the roof deck where it intersects the parapet wall. Asphalt-saturated felt is then installed over the flashing and counterflashing. See Figure Flat roofs are pitched to direct rainwater and melting snow toward the gutters and downspouts. Nail holes are avoided in the upper felt layers.
43Gravel stops are used to finish the edges of built‑up roofs. Built‑up roof coverings are installed by roofing contractors who specialize in built-up roofing. Carpenters are not involved in the application of the built‑up roof; however, they may perform certain preparatory work such as installing gravel stops, cant strips, and flashing. See Figure 55‑42.