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Greek: the ridge height is 1 ⁄ 9 to 1 ⁄ 7 the span (an angle of 12.5° to 16°); Roman: the ridge height is 2 ⁄ 9 to 1 ⁄ 3 the span (an angle of 24° to 34°); Common: the rafter length is 3 ⁄ 4 the span (about 48°); Gothic: the rafters equal the span (60°); and; Elizabethan: the rafters are longer than the span (more than 60°). [7]
A gable roof [1] is a roof consisting of two sections whose upper horizontal edges meet to form its ridge. The most common roof shape in cold or temperate climates, it is constructed of rafters, roof trusses or purlins. The pitch of a gable roof can vary greatly.
Compass rafter: A rafter curved or bowed on the top (the top surface of a rafter is called its "back") or both the top and bottom surfaces. Curb rafter: The upper rafters in a curb (kerb, gambrel, Mansard roof) roof. Hip rafter (angle rafter): The rafter in the corners of a hip roof. The foot of a hip rafter lands on a dragon beam.
[5] [6] The term truss has often been used to describe any assembly of members such as a cruck frame [7] [8] or a couple of rafters. [ 9 ] [ 10 ] One engineering definition is: "A truss is a single plane framework of individual structural member [sic] connected at their ends of forms a series of triangle [sic] to span a large distance".
Key:1: ridge beam, 2: purlins, 3: common rafters. This is an example of a "double roof" with principal rafters and common rafters. 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.
This is accomplished by using metal ties fastened to each rafter or truss. This is not normally a problem in areas not prone to high wind or extreme weather conditions. In the UK, a concrete tiled roof would normally have rafters at 600 mm (24 in) centers, roof battens at 300 mm (12 in) centers and ceiling joists at 400 mm (16 in) centers.
The triangular faces of the roof are called the hip ends, and they are bounded by the hips themselves. The "hips" and hip rafters sit on an external corner of the building and rise to the ridge. Where the building has an internal corner, a valley makes the join between the sloping surfaces (and is underlain by a valley rafter). Hip roofs have ...
Sight distance, in the context of road design, is defined as "the length of roadway ahead visible to the driver".[1] Sight distance is how far a road user (usually a vehicle driver) can see before the line of sight is blocked by a hill crest, or an obstacle on the inside of a horizontal curve or intersection.