Different Pitched Roofs

Dual-pitched roof

iii) Trussed or Framed Roof

A timber roof truss is a structural framework of timbers designed to bridge the space above a room and to provide support for a roof. Trusses usually occur at regular intervals, linked by longitudinal timbers such as purlins. The space between each truss is known as a bay.[1]

Timber roof trusses were a medieval development. Earlier roofs had been supported by coupled rafters – pairs of rafters linked by horizontal beams. But such roofs were structurally weak, and lacking any longitudinal support were prone to racking, a collapse resulting from horizontal movement.

Ref:

Wikipedia on "single pitched roof"

http://en.wikipedia.org/wiki/Mono-pitched_roof

Wikipedia on "double pitched roof"

http://en.wikipedia.org/wiki/List_of_roof_shapes

Wikipedia on "trussed roof"
http://en.wikipedia.org/wiki/Timber_roof_truss

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.

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.

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.

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.

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.