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In the imperial measurement systems, "pitch" is usually expressed with the rise first and run second (in the US, run is held to number 12; [1] e.g., 3:12, 4:12, 5:12). In metric systems either the angle in degrees or rise per unit of run, expressed as a '1 in _' slope (where a '1 in 1' equals 45°) is used.
The rafter table is expressed in inches, and the higher the numerical value of the pitch, the greater the difference between side cut angles within a given pitch. Only a level roof, or a 0 pitch will require a 45° angle side cut (cheek cut) for hip and jack rafters.
Bonnet roof: A reversed gambrel or Mansard roof with the lower portion at a lower pitch than the upper portion. Monitor roof : A roof with a monitor; 'a raised structure running part or all of the way along the ridge of a double-pitched roof, with its own roof running parallel with the main roof.'
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.
Key: 1: queen posts, 2: tie beam, 3: straining beam, 4: principal rafters. A queen post truss has two principal rafters and two vertical queen posts . [ 5 ] The queen post truss extends the span, and combined with spliced joints in the longer members extends the useful span for trusses of these types.
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 the advantage of giving a compact, solid appearance to a structure. The roof pitch (slope) may vary.
This avoids details which require a great deal of work or cost and which are prone to damage. If the pitch or the rafter lengths of the two roof sections are different, it is described as an 'asymmetrical gable roof'. A gable roof on a church tower (gable tower) is usually called a 'cheese wedge roof' (Käsbissendach) in Switzerland.
A hammer-beam is a form of timber roof truss, allowing a hammerbeam roof to span greater than the length of any individual piece of timber.In place of a normal tie beam spanning the entire width of the roof, short beams – the hammer beams – are supported by curved braces from the wall, and hammer posts or arch-braces are built on top to support the rafters and typically a collar beam.