![]() ![]() ![]() They extend up from the top of the wall plate at a right angle (90°) to abut into an existing hip rafter. Jack rafterĪ jack rafter is any rafter that is shorter than the whole length of the sloping roof, such as one that begins or ends at a hip or valley. To put it another way, it’s the main rafter at the bottom of a hip and valley roof. The valley rafter is the rafter in the valley line that joins the ridge to the wall plate along the meeting line of two sloped sides of a roof that are perpendicular to each other in a roof framing system. Traditional stick-framing techniques can be used to make these rafters, or they can be integrated in a pre-engineered steel or timber truss system. A hip rafter connects to the ridge at a 45-degree angle, as opposed to ordinary roof rafters, which run perpendicular to the peak of the roof. These are rafters that runs diagonally between the roof ridge and the top of the wall plate, forming a hipped roof. Smaller rafters located in between the principals at both ends.įigure 8: The components of a hip and valley roof Hip rafter The roof is now ready for the next type of rafter once the ridge board has been installed. The common roof rafter is used to calculate the roof’s height and where the ridge board should be installed. This style of rafter starts at an outside wall and extends all the way to the roof’s ridge board or peak. The basic gable roof is constructed using a common rafter. 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 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. Note that these are normally only required to trussed rafter roofs and not for traditional purlin and rafter roof construction.Rafters are loading bearing structural members that are used in roof construction. This is the right way to fix truss clips connecting the rafter and wall plate. Vertical strapping at eaves pitched roofsĪt eaves level, vertical straps 1m long should be fixed as shown in the diagram opposite at a maximum of 2m centres. Effective strapping at gable wallĮach strap should be fixed as shown in the diagram opposite with noggins between the rafters to support the metal strap along its whole length. Gable walls need to be strapped to the roof at the maximum 2m centres using 30 x 5m galvanised mild steel straps. This diagram illustrates the typical arrangement of a rafter and purlin roof and shows the dimensions referred to in the tables above. Roof pitch between 30 and 45 degrees strength class C24 Size of purlins in mm ![]()
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