Purlin Roof Framing Diagram

The rafters are the beams of wood angled upward from the ground.

Purlin roof framing diagram.

Also referred to as secondary structurals this type of framing runs in between primary framing elements creating a structure within a structure much like cross beams in a wooden building. In wide structures rafters are often supported by purlin. Where the tie beam joins the wall framing we have the tying joint. The purlin are ultimately used to fasten the roof steel providing a diaphragm effect along with the siding when properly engineered and installed.

When a tie beam joins the feet of principal rafters the result is a triangle a rigid struc tural shape. Component w cosθ perpendicular to the plane of the sheathing and a downslope. A view of a roof using common purlin framing. Shed roof framing process explained step by step instructions.

Figure 2 2 roof framing terms. Framing a shed roof is similar to framing a wall. The fascia board is the bottom plate and the ridge board the top plate. About the base of the purlin based on the free body diagram shown in figure 3.

This article and series of illustrated diagrams shows you all the parts of a basic roof truss king truss and queen truss. Secondary framing is an important component of many pre engineered metal buildings. They meet at the top of the gable at a ridge beam which has extra bracing to attach it to the rafters. Outward thrust of the roof planes.

Purlins support the loads from the roof deck or sheathing and are supported by the principal rafters and or the building walls steel beams etc. Component w sinθ in the plane of the sheathing. Line length is the hyptenuse of the triangle whose. There are many types of roof trusses as wall as many types of roofs more types than there are parts.

The roof truss structure and design is integral to roof structural integrity and shape. Tying joints are usually the only connections in a frame that must resist tension. 1 8 pitch is given so 24 x 1 8 equals 3 or unit of rise in inches. Stick to the basics of simplified design and use dimensions that don t generate waste.

This view is from the inside of the building below the roof. Keep it simple and remember. Purlins are dimensional lumber that are fastened to the top chord of trusses connecting them together for bracing purposes.