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All About Roofs: Pitches, Trusses and Framing (page 1 of 2)

Learn about the basic types of pitched roofs and roof frame designs.

Excerpted from Do It Yourself Home Improvement

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Roofs may be pitched (angled), or "flat" (which, in reality, is very slightly angled). Most roofs are pitched. There are many types of pitched roofs to suit different situations. As a result, there are many variations on the basic design and numerous combinations of design elements with construction methods.

Types of Pitched Roofs

Four main designs of pitched roofs are shown here. There are many variations on these themes. Roofs are usually defined according to their shape. Each type can be built in different ways, and from different materials.

Gabled
The roof slopes around a triangular extension of the end wall. This piece of wall is the gable.

Gable Roof Creates More Attic Space for Home

Courtesy of DK - Do It Yourself Home Improvement © 2009 Dorling Kindersley Limited

Hipped
A hip is the joint between two adjacent slopes of a roof. Some complex roofs have several hips.

Hipped Roof has Joint Between Slopes

Courtesy of DK - Do It Yourself Home Improvement © 2009 Dorling Kindersley Limited

Shed
This simple roof has only one slope. It is commonly used on lean-to structures, such as additions.

Shed Roof has Only One Slope

Courtesy of DK - Do It Yourself Home Improvement © 2009 Dorling Kindersley Limited

Mansard
A modified version of the pitched roof that creates a spacious living area in the roof space.

Mansard Roof Creates Spacious Living Area in Roof

Courtesy of DK - Do It Yourself Home Improvement © 2009 Dorling Kindersley Limited

Roof Detailing

Ridges, hips and valleys are the corners or joints where a roof changes direction; they are the points at which pitched roofs meet. Verges, abutments and eaves are the "edges" of a roof. The eaves are horizontal joints between a roof and a wall, whereas the verges are angled joints between a roof and a gable wall. Not all roofs feature all of these details, and some of them can be constructed in a number of ways.

Courtesy of © 2007 Dorling Kindersley Limited

Pitched Roof Frames

A pitched roof has a network of frames to support the structure and its covering. There are two main types of wooden frames — a cut roof and a trussed roof — which are sometimes combined to achieve more complex roofs. Both types of construction will support any common roof coverings.

Cut Roof Frame
Traditionally, all roofs were "cut" — carpenters cut rafters on site during construction. To cover greater spans, some of the roof’s weight may be transferred onto internal loadbearing walls using purlins (beams that brace the rafters; shown right). This forms a "double" roof. Although they are labor-intensive, single- and double-cut roofs are still constructed.

Common Trussed Roof Frame
Often referred to as A-frames because of their shape, modern trusses (lumber frames) are manufactured off-site by specialist companies. The A-frame combines rafters, joists and jacks. A roof is made up of several A-frames. Because of technological advances in calculating the stresses and loading requirements of roof lumber, trusses can be made slimmer than the boards in a cut roof. Trusses are manufactured in a number of different shapes and sizes to suit the needs of various types of roofs. For example, some trusses are designed to leave a lot of open space in a roof, so that it can be used as a room. Lean-to, or shed, trusses are commonly used for additions.

Common Trussed Roof Frame

Courtesy of DK - Do It Yourself Home Improvement © 2009 Dorling Kindersley Limited

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Excerpted from Do It Yourself Home Improvement

© Dorling Kindersley Limited 2009

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