The principal rafters, when combined with the principal purlins, constitute a very stable roof construction system. Principal rafters run from the roof’s ridge to the wall plate they’re a little heavier than ordinary rafters, and they’re usually framed into a tie beam at a corner post, story post, or chimney post. They are commonly used to carry a purlin and sit directly on a tie beam. Principal rafters are the largest form of rafter found at the ends of a roof structure in a timber-framed roof. It could also be left as open space in an attic.įigure 7: Plan view of roof framing members Principal rafter
As a result, the area in the roof is left as a vaulted ceiling that may be finished with insulation and drywall. The rafters and external walls are then connected with ceiling joists. Hence, timber rafters are usually constructed in form of A-shape, consisting basically of the rafters, rafter ties, and ridge board/hips. Trussed rafters are generally employed for large scale timber roof construction, but direct timber rafters are more efficient for small scale constructions. Timber rafters rely on nails or screws for connection. The number of common rafter units needed for each project is mostly determined by the roof’s size and scope, as well as the distance each unit rafter must span. Many common, or general purpose, rafters make up each roof. The common rafters form the sloped sides of the triangle on a traditional gable roof, which has a triangular shape. Rafters are part of a basic wood framing system and are made of wood lumber.
Timber rafters are popular options in timber/wooden roof structures. The spacing of rafters can be determined from the design requirements, type of roof sheeting to employed, type and spacing of purlins, availability of materials, etc.įigure 4: Steel portal frame consisting of stanchions and rafters Timber Rafters
#BARGE RAFTER SERIES#
Furthermore, they are constructed in series and laid parallel to each other at usually a constant spacing. Rafters can be constructed using steel or timber. They are also important members for resisting upward wind pressure on roofs. They typically run from the ridge board or hip of the roof at a sloping angle to the roof wall plate, columns, or roof beams, depending on the support system adopted for the entire roof structure.īy implication, rafters receive the load from the roof covering/sheeting, accessories, and other services that may be attached to it. If the ends of the rafters on your home are not properly capped it is a pretty simple thing to fix and can save a lot of costly repairs later on.Rafters are loading bearing structural members that are used in roof construction. Fortunately the roof needs replacement as well, which will make replacement of the rafter easier-and should be replaced in conjunction with the roof replacement (these rafters are very difficult to replace without removing the roofing above it). In this case more than the end is deteriorated and most likely the whole rafter will need to be replaced. This next picture shows what will happen if it is not properly capped. This first picture shows good examples of nicely capped barge rafters (foreground and background). It is important that the top edge be properly flashed with either roofing materials or a metal flashing to prevent decay/rot in the ends of the rafter. Often these rafters extend past the eaves to create a place to hide the end of the gutter or as a decorative element. The fascia board on the Gable end of a home is called a "barge rafter".
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