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Chapter 16 Roof Designs. Chapter 16 Roof Designs.

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Presentation on theme: "Chapter 16 Roof Designs. Chapter 16 Roof Designs."— Presentation transcript:


2 Chapter 16 Roof Designs

3 Objectives • Identify and sketch 12 different types of basic roof designs. • Draw a roof that has a typical roof slope (pitch). • Describe the construction of a typical frame roof. • Explain the importance of proper attic ventilation and roof flashing. • Compare the advantages and disadvantages of new roofing materials. • Explain the purpose of a roof plan.

4 Types of Roofs The roof greatly affects the overall appearance of a house Many standard styles Style should complement the basic design

5 Gable Roof Triangular with a gable at both ends
Easy to build and sheds water well Applicable to most house designs

6 Winged Gable Roof Attractive design feature
Gable roof, extended at the peak Requires lookout rafters

7 Hip Roof Sloped roof section or hip at ends
Slightly more difficult to build than gable roof Does not provide for ventilation as well as others

8 Dutch Hip Roof Hip roof with a small gable at either end
Steeper gables than hips Gables can be used for ventilation

9 Flat Roof Most economical to build
Requires “built-up” or membrane roof covering Popular in warm climates

10 Shed Roof More pitch than flat roof
Used for additions or with other roof styles Less than 3:12 pitch requires a built-up roof

11 Gambrel Roof Also known as “barn roof” Two different slopes
Provides additional headroom

12 Mansard Roof French design Provides additional living space
Difficult to build

13 A-Frame Roof Provides roof and walls for structure
Pitch allows for smaller second floor Popular for cottages, homes, churches

14 Butterfly, Folded Plate, and Curved Panel Roofs
Limited residential construction Used in commercial construction Can cause drainage problems

15 Contemporary Roof Types
Warped roof: Limitless in design Common shape is hyperbolic paraboloid Made from concrete, plywood, or plastic Expensive to build Free-form roof: Freedom with design Any shape can be formed with fabric and frame Strong and weather resistant Limited residential use

16 Green Architecture Living Roofs: Covered with soil, capable of growing plants Benefits: Used for growing food Provides excellent insulation Reduces storm water run-off Creates habitat for wildlife May lower air temperatures in large cities

17 Traditional Frame Roof Construction
Before designing a roof: Consider the features of traditional frame roof construction Understand the features impact on the design

18 Rafters Rafter: Structural element of the roof that supports the sheathing Common rafters lay perpendicular to wall plate Rafters extend from roof’s ridge to plate or beyond Several types

19 Rafters

20 Rafters Rafters are cut to proper lengths by locating ridge cut, seat cut, plumb cut, and tail cut

21 Rafters Layout of rafter cuts are determined by: Additional factors:
Roof slope (roof pitch) Clear span Additional factors: Rise Run

22 Rafters

23 Rafters Roof slope (roof pitch) is slant of roof Shown on drawing as:
Slope ratio diagram Fractional pitch

24 Rafters Slope diagram Fractional pitch is rise/clear span
Indicated by triangle Shows ratio between rise and run of roof Run is always expressed as 12 units Fractional pitch is rise/clear span Pitch = Rise/Clear Span

25 Rafters Rafter sizes depend on: Spanned distance Rafter spacing
Supported weight

26 Rafters Rafters may serve as ceiling joists on low-sloped roofs

27 Cornice Cornice: Roof’s overhang at the eave line that forms connection between roof and side walls Three types used in residential construction: Open cornice Box cornice Close cornice

28 Open Cornice Used with exposed-beam construction, contemporary, or rustic designs Rafter ends: Exposed Tapered or curved

29 Box Cornice Space between the ends of projecting rafters and wall is enclosed with a soffit board Three basic types: Narrow box Wide box with lookouts Wide box without lookouts

30 Wide Box Cornice With Lookouts

31 Close Cornice Rafter does not project beyond wall
Roof is terminated by frieze board and molding

32 Rake or Gable End Gable end (rake): Extension of gable roof beyond exterior walls of house Proportions should be similar to cornice Special framing is used for wide overhang Close rake is least expensive to build

33 Rake or Gable End Framing for gable end with wide overhang

34 Roof Trusses Roof truss Information needed to purchase a truss:
Assembly of members that form rigid framework that supports roof Information needed to purchase a truss: Roof span Roof pitch Truss spacing Roof load

35 Roof Trusses Adequate roof load is 40 pounds per sq. ft.
Lightweight wood trusses can span distances of 20' to 32' Typical residential trusses are 2  4 or 2  6 lumber Gussets fasten members of wood truss together

36 Roof Trusses Prefabricated trusses Common wood trusses:
Less expensive than conventional framing Available in standard widths and pitches Common wood trusses: W-type truss King-post or K-post truss Scissors truss

37 W-Type Truss

38 K-Post Truss

39 Scissors Truss Scissors truss

40 Raised Heel Truss When bottom chord of truss extends beyond exterior wall Provides space for additional insulation

41 Ventilation Attic ventilation is a necessity
Reduces moisture condensation under sheathing Helps cool house interior Screened openings or ventilators provide attic ventilation Ventilator openings should be at least 1/300th of ceiling area

42 Ventilation Types of ventilators Gable ends and underside of overhang
Ridge and soffit ventilator

43 Flashing Flashing repels water from areas of potential leakage
Used where roof contacts a wall, chimney, roof valley, or at any roof penetration Placement is beneath surface material per specifications

44 Flashing May be weather-resistant metal
Aluminum, copper, galvanized sheet metal Roof valley flashing can be metal or two layers of 90# roll-type roofing Metal drip edge flashing Prevents water from entering behind shingles Protects fascia and rake boards

45 Chimney Flashing Composed of shingle flashing and counterflashing

46 Gutters and Downspouts
Collects water from roof and directs it to downspout that diverts it away from house Prevents water from running directly off eaves and splattering house Pitched 1" to 1.5" per 20' Available in several styles and materials

47 Roof Sheathing and Roofing
Roof sheathing supports roofing material Generally plywood or other approved panel product Thickness depends on rafter spacing 1/2" sheathing-grade plywood is used when rafters are 16"OC

48 New Roofing Materials Asphalt laminate shingles Metal roofing

49 Asphalt Laminate Shingles
Thicker, heavier, and more wind resistant than traditional asphalt shingles Appear three-dimensional

50 Roofing Materials Metal roofing:
Gaining wider acceptance for residential construction Resists high winds Simulates other roofing materials

51 Roof Plan Roof plan—Top view plan that shows information needed to construct roof Shape Roof pitch Size and location of framing Size and location of roof vents

52 Roof Plan Roof framing plan shows: Exterior house walls
Exterior roof lines Size and location of all roof framing members Any additional information needed for roof construction

53 Employability Computer ethics
Unethical to use computer for personal activities without permission Unethical to access confidential information, download copyrighted material, or harass others Many organizations monitor computer users

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