1. EDT 300 - Cabin Design Project - Roofs1 Weekend Cabin Retreat Project Roofs Sacramento City College EDT 300 Kenneth Fitzpatrick, P.E.

2. 2EDT 300 - Cabin Design Project - Roofs Types of Roofs u The appearance of a house is affected greatly by the roof lines and material. u The roof should compliment the structure.

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5. 5 Gable Roof u The gable roof is very popular. u Easy to build. u Sheds water well. u Provides for ventilation. u Can be used on a variety of house designs.

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7. 7 Hip Roof u The hip roof is slightly more difficult to build than a gable roof. u The hip roof is a very popular choice. u Does not provide for ventilation as well as gable roof. u Increased chance of leaks because of hips and valleys.

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9. 9 Flat Roof u The flat roof is the most economical roof to construct. u Doesn’t add much to the appearance of the house. u Requires “built-up” or membrane roof covering instead of conventional shingles. u A built-up roof consists of layers of roofing felt and tar. u Usually pitched about 1/8” to 1/2” to provide for drainage.

10. 10EDT 300 - Cabin Design Project - Roofs Flat Roof u The flat roof is popular in warmer areas of the country where wide overhangs are desirable for shade and where little or no snow falls.

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12. 12EDT 300 - Cabin Design Project - Roofs Shed Roof u The shed roof is similar to flat roof but has more pitch. u Frequently used for additions to existing buildings. u A built-up roof is often required. u Pitch must be 3:12 to use shingles.

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14. 14EDT 300 - Cabin Design Project - Roofs Butterfly Roof u The butterfly roof has not been used widely in the past. u Provides plenty of light and ventilation. u Drainage is the problem. u Flashings must extend far up the roof to prevent leaks.

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16. 16EDT 300 - Cabin Design Project - Roofs Gambrel Roof u The gambrel roof is sometimes called a “barn roof”. u It has been used extensively for barns. u Provides the additional headroom required for the “Dutch colonial” building style.

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18. 18EDT 300 - Cabin Design Project - Roofs Winged Gable u The winged gable is a variation on the gable roof. u Ridge peaks are extended to form a point.

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20. 20EDT 300 - Cabin Design Project - Roofs Dutch Hip u The dutch hip is a combined gable and hip configuration.

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22. 22EDT 300 - Cabin Design Project - Roofs Mansard Roof u The mansard roof has not been popular for several years. u Is returning to popularity. u Is a French design. u Is more difficult to construct than hip or gable.

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24. 24EDT 300 - Cabin Design Project - Roofs A-Frame Roof u The A-frame is a combined wall and roof. u Originally used for cottages. u Now is used for homes, churches, and other structures.

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26. 26EDT 300 - Cabin Design Project - Roofs Curved Plate Roof u Similar to Folded Plate roof. u Limited residential application. u Some use in prefabricated modules.

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28. 28EDT 300 - Cabin Design Project - Roofs Folded Plate Roof u The Folded Plate Roof is a contemporary design. u It is finding some limited application in residential construction. u Quite popular for motels and small commercial buildings. u Many modular, prefabricated units have this type of roof.

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30. 30 Traditional Frame Roof Construction

31. 31EDT 300 - Cabin Design Project - Roofs Rafters u Roof covering material is supported by roof framing. u The framing must be strong and rigid. u Roof framing consists of several distinct structural elements. u The first and most basic of these elements is the rafter.

32. 32EDT 300 - Cabin Design Project - Roofs Rafters u Common rafters are perpendicular to the top wall plate. u They extend from the plate or beyond to the ridge of the roof. u Note that several types of rafters other than common rafters are identified.

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34. 34EDT 300 - Cabin Design Project - Roofs Rafters u Rafters are cut to the proper dimensions by locating the ridge cut, seat cut, plumb cuts, and tail cut. u The precise layout of these cuts is determined by u The slope or pitch of the roof. u The inside width or clear span of the building.

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36. 36EDT 300 - Cabin Design Project - Roofs Rafters u Terms that must be understood before calculating rafter dimensions and roof pitch are: u Rise. u Run. u Span.

37. 37EDT 300 - Cabin Design Project - Roofs Terminology u Rise - the vertical distance measured from the top of the wall plate to the underside of the rafters.

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39. 39EDT 300 - Cabin Design Project - Roofs Terminology u Run - one-half of the distance of the clear span.

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41. 41EDT 300 - Cabin Design Project - Roofs Terminology u Clear Span - is the horizontal distance from the inside of one stud wall to the inside of the opposite stud wall.

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43. 43EDT 300 - Cabin Design Project - Roofs Roof Slope u Roof slope may be indicated on the drawings by: u A slope ratio diagram u A fractional pitch indicator u An angular dimension. u The angular dimension method is seldom used u It is difficult to measure as accurately as either of the other methods.

44. 44EDT 300 - Cabin Design Project - Roofs Roof Slope u When designing a roof, use a standard roof pitch. u 3 in 12. u 4 in 12. u 5 in 12. u 6 in 12.

45. 45EDT 300 - Cabin Design Project - Roofs Rafters u Select rafters based on u The distance to be spanned. u The spacing of the rafters. u The weight to be supported. u Rafters for low-slope roofs may also serve as ceiling joists.

46. 46EDT 300 - Cabin Design Project - Roofs Roof Weights Per Square Foot u A “light roof” is one that weighs less than 4 lbs per square foot. u Examples: u Cedar shake roof. u Composition roof. u Metal roof.

47. 47EDT 300 - Cabin Design Project - Roofs Roof Weights Per Square Foot u A “heavy roof” is one that weighs more than than 4 lbs per square foot. u Examples u Slate. u Clay tile. u Concrete tile.

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51. 51EDT 300 - Cabin Design Project - Roofs Cornice u The cornice is the overhang of the roof at the eaves line. u It forms a connection between the roof and the side walls. u In a gable roof, the cornice is formed around two sides of the building u In a hip or flat roof, the cornice is formed around all four sides of the building.

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53. 53EDT 300 - Cabin Design Project - Roofs Cornice u Three types in residential construction: u Open cornice u Box cornice u Close cornice

54. 54EDT 300 - Cabin Design Project - Roofs Open Cornice u The Open Cornice may be used with: u Exposed beam construction. u Contemporary designs u Rustic designs u Rafter ends are exposed and are usually tapered or curved to prevent a bulky appearance.

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56. 56EDT 300 - Cabin Design Project - Roofs Three Types of Box Cornice u Narrow Box. u Wide Box with Lookouts. u Wide Box without Lookouts.

57. 57EDT 300 - Cabin Design Project - Roofs Narrow Box Cornice u Usually between 6” and 12” wide. u The soffit board is nailed directly to the bottom side of the rafters. u Usually used for Cape Cod or colonial homes.

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59. 59EDT 300 - Cabin Design Project - Roofs Wide Box Cornice with Lookouts u Is usually between 6” and 12” wide. u Requires additional support members called “lookouts” for fastening the soffit u The soffit board is nailed directly to the bottom side of the rafters.

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61. 61EDT 300 - Cabin Design Project - Roofs Wide Box Cornice without Lookouts u Has a sloped soffit u The soffit material is nailed tot he underside of the rafters. u Frequently used where overhangs are very wide.

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63. 63EDT 300 - Cabin Design Project - Roofs Close Cornice u Is one in which the rafter does not project beyond the wall. u The roof is terminated by a frieze board and molding.

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65. 65EDT 300 - Cabin Design Project - Roofs Rake or Gable End u Is the extension of a gable roof beyond the end wall of the house. u The overhang should be about the same size as the cornice. u If a close cornice is used, a close rake should be used.

66. 66EDT 300 - Cabin Design Project - Roofs Rake or Gable End u Wide overhangs provide side wall protection and less frequent painting. u In California, wide overhangs provide shading from hot summer sun.

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68. 68EDT 300 - Cabin Design Project - Roofs Roof Trusses u Roof trusses are an assembly of members that form a rigid framework of triangular shapes. u They permit wide unsupported spans with a minimum amount of material.

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78. 78EDT 300 - Cabin Design Project - Roofs Roof Trusses u Lightweight wood roof trusses are designed to span distances of 20 to 32 feet. u Many times trusses are less expensive than conventional framing. u Time and expense is saved.

79. 79EDT 300 - Cabin Design Project - Roofs Roof Trusses u Prefab trusses for standard widths are readily available. u Custom trusses for non-standard dimensions are factory produced. u Most trusses are made from 2 x 4 lumber. u 2 x 6 may be used for wider spans and heavier loads.

80. 80EDT 300 - Cabin Design Project - Roofs Roof Trusses u W-type truss u King-post truss u Scissors truss u are commonly used in residential construction.

81. 81EDT 300 - Cabin Design Project - Roofs Roof Trusses u Most are designed to be installed at 24” on center. u Ceiling materials are nailed directly to the bottom of the truss. u Information required to make u Span u Roof pitch u Spacing of the trusses u Anticipated roof load.

82. 82EDT 300 - Cabin Design Project - Roofs Ventilation u Adequate attic ventilation is critical. u Moisture will form on the underside of the roof sheathing and damage will result. u A well-ventilated attic will help to cool the house in the summer.

83. 83EDT 300 - Cabin Design Project - Roofs Ventilation u Ventilation is usually achieved by louvered openings on the gable end. u Ridge ventilators are also available. u The total are of the ventilation openings should be 1/300 of the ceiling area. u 1200 sq ft. Ventilation openings at least 4 sq ft.

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92. 92EDT 300 - Cabin Design Project - Roofs Flashing u Flashing should be used where u the roof comes in contact with a wood or masonry wall. u At a chimney. u At a roof valley. u Common flashing materials: u Aluminum u Copper u Galvanized sheet steel.

93. 93EDT 300 - Cabin Design Project - Roofs Flashing u The flashing is placed under the roofing material a sufficient distance to prevent the penetration of water. u Roof valleys u flash with metal or two thicknesses or roll type roofing. u Asphalt roofing mastic is used under the shingles adjacent to the valley to aid in waterproofing this area.

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95. 95EDT 300 - Cabin Design Project - Roofs Flashing u A small metal edging is normally used at the gable and eave line to act as a drip edge u Its purpose is to prevent water from entering behind the shingles and to protect the fascia boards.

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97. 97EDT 300 - Cabin Design Project - Roofs Gutters and Downspouts u Gutters collect the water and prevent it from running directly off the eaves and splattering the house. u Downspouts are the pipe to channel the roof water to the ground. u Copper, vinyl, aluminum and galvanized sheet steel are common materials.

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103. 103EDT 300 - Cabin Design Project - Roofs Roof Sheathing and Roofing u Sheathing is placed over rafters u Supports the roofing material u May be u planks u individual boards u plywood u Plywood is most common.

104. 104EDT 300 - Cabin Design Project - Roofs Roof Sheathing and Roofing u Sheathing thickness varies with the spacing of the rafters and supporting beams. u Sheets are laid with grain perpendicular to the rafter u Joints are staggered

105. 105EDT 300 - Cabin Design Project - Roofs Roofing u Common materials: u asphalt singles u wood shingles u tile u slate u roll roofing u copper, aluminum and galvanized sheet steel u layers of felt and tar u rubber membrane roofing

106. 106EDT 300 - Cabin Design Project - Roofs Roofing u Factors affecting choice of material: u cost u local codes u roof pitch u design u individual preference

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