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Roof pitch is the steepness of a roof expressed as a ratio of inch(es) rise per horizontal foot (or their metric equivalent), or as the angle in degrees its surface deviates from the horizontal. A flat roof has a pitch of zero in either instance; all other roofs are pitched .
Two king post trusses linked to support a roof. 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.
For longer span rafters, building materials manufacturers have created laminated veneer lumber (LVL) rafters that can be 2–5 times longer than typical wood rafter. In the US, most wood rafters have maximum length of 20 feet (6.1 m). [5] If a longer rafter is needed, LVL is an alternative.
A warm roof is a roof that is not ventilated, [9] where the insulation is placed in line with the roof pitch. [10] A hot roof is a roof designed not to have any ventilation and has enough air-impermeable insulation in contact with the sheathing to prevent condensation [ 11 ] such as when spray foam insulation is applied directly to the under ...
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.
The simplest form of roof framing is a common rafter roof. This roof framing has nothing but rafters and a tie beam at the bottoms of the rafters. The next step in the development of roof framing was to add a collar, called a collar beam roof. Collar beam roofs are suitable for spans up to around (4.5 meters). [5]
The final rafter fits on top of the previous rafter and under the very first one. The rafters are then tied before the temporary support is removed. The structure is most effective at lower pitches where there is minimal spreading force exerted at the ringbeam, most being transferred directly downward.
In engineering, span is the distance between two adjacent structural supports (e.g., two piers) of a structural member (e.g., a beam). Span is measured in the horizontal direction either between the faces of the supports (clear span) or between the centers of the bearing surfaces (effective span): [1] A span can be closed by a solid beam or by ...