Purlin Prop Hip Roof

Hip rafter in a hip roof these are fixed to the jack rafters.

Purlin prop hip roof. When rafter spans are too great a purlin is introduced to break the span by transferring the loads to gable walls or in this case to the hip rafters. Hip rafters are simply called hips and are shown here as brown. Crown rafter only found in hipped roofs in which it forms the centre joint between jack rafters. Hip roofs can be designed over square shaped buildings as well as on rectangular ones.

Stabilization typically involves installation of a purlin system. In a rafter and purlin loft roof the purlins provide the most tangible support to the roof and are the largest and strongest timbers in the structure. Rotations angles involved with a purlin in compound hip roof system. All angles can be found on the chappell universal framing square.

Rafters are sloped beams that run from the roof s ridge to the eaves. Purlins on a roof frame serve the purpose of preventing rafters from being over spanned and sagging. Rick arnold frequent contributor to fine homebuilding and the journal of light construction presenter at jlc live the katz roadshow the remodeling show. But a purlin is applied directly onto the roof rafters running perpendicular between them while a batten is nailed to roof sheathing or applied over an existing roof for installation of a new roof.

If you see sagging rafters recommend stabilization by a qualified contractor. A hip rafter extends from the wall plate to the ridge in the angle of a hip roof. Hip roofs have hip rafters which are oriented diagonally to the ridge and outside walls. The design of hip roofs can follow triangular sides as well as a combination of triangular and trapezoidal sides.

The purlins are supported by vertical or slightly angled bracing. The angles between these two lines and the hip mark the downslope ends of the mortises for the main and adjacent purlins in the side of the hip. Some hip roof designs follow pyramid shapes whereas others may have more symmetrical structures. The two words are often used interchangeably and both are long strips usually wood used for the attachment of roofing material.

A purlin is a horizontal piece of timber or metal which supports the roof s rafters or decking and helps to prevent your roof from sagging. Purlin side cuts and lip cuts fig. The purlins are therefore carrying half of the roof load and yet the load transfer is only through one third of the timber plus the mechanical fixing of one clout nail.