16 Roof Designs Chapter Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Objectives Identify and sketch 12 different.

16Roof Designs

Chapter

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.

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.


Types of Roofs

• The roof greatly affects the overall appearance of a house

• Many standard styles• Style should complement the basic design


Gable Roof

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


Winged Gable Roof

• Attractive design feature• Gable roof, extended at the peak• Requires lookout rafters


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


Dutch Hip Roof

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


Flat Roof

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


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


Gambrel Roof

• Also known as “barn roof”• Two different slopes• Provides additional headroom


Mansard Roof

• French design• Provides additional living space• Difficult to build


A-Frame Roof

• Provides roof and walls for structure• Pitch allows for smaller second floor• Popular for cottages, homes, churches


Butterfly, Folded Plate, and Curved Panel Roofs

• Limited residential construction• Used in commercial construction• Can cause drainage problems


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


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

Green


Traditional FrameRoof Construction

• Before designing a roof:– Consider the features of traditional frame roof

construction – Understand the features impact on the design


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


Rafters


Rafters

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


Rafters

• Layout of rafter cuts are determined by:– Roof slope (roof pitch)– Clear span

• Additional factors:– Rise– Run


Rafters


Rafters

• Roof slope (roof pitch) is slant of roof• Shown on drawing as:

– Slope ratio diagram– Fractional pitch


Rafters

• Slope diagram– 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


Rafters

• Rafter sizes depend on:– Spanned distance– Rafter spacing– Supported weight


Rafters

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


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


Open Cornice

• Used with exposed-beam construction, contemporary, or rustic designs

• Rafter ends:– Exposed– Tapered or curved


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


Wide Box Cornice With Lookouts


Close Cornice

• Rafter does not project beyond wall• Roof is terminated by frieze board and molding


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


Rake or Gable End

• Framing for gable end with wide overhang


Roof Trusses

• Roof 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


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


Roof Trusses

• Prefabricated 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


W-Type Truss


K-Post Truss


Scissors Truss

• Scissors truss


Raised Heel Truss

• When bottom chord of truss extends beyond exterior wall

• Provides space for additional insulation


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


Ventilation

• Types of ventilators– Gable ends and underside of overhang– Ridge and soffit ventilator


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


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


Chimney Flashing

• Composed of shingle flashing and counterflashing


Gutters and Downspouts

• Gutter– 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


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


New Roofing Materials

• Asphalt laminate shingles• Metal roofing


Asphalt Laminate Shingles

• Thicker, heavier, and more wind resistant than traditional asphalt shingles

• Appear three-dimensional


Roofing Materials

• Metal roofing:– Gaining wider acceptance for residential

construction– Resists high winds– Simulates other roofing materials


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


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


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

16 Roof Designs Chapter Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Objectives Identify and sketch 12 different.

Documents

educational use

builtup roof slide

roof run

roof styles

flat roof

rafters roof slope roof

membrane roof

barn roof