Steel Roof Purlin Span

The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to.

Steel roof purlin span.

As per as1684 and as4055 spanman adopts a nett pressure coefficient applied along the full length of the purlin of cpn 2 0 for non cyclonic zones n1 to n6 and cpn 2 5 for cyclonic zones c1 to c4. Cleated or bracketed fixing only no flange bolting. The safe spans below are suitable for sheds and class 1 structures with the following assumptions. Dead load will be the actual weight of the roof steel and the roof purlins.

Meanwhile there are two kinds of purlin span for metal roof based on the shapes which are the c purlins and z purlins. Max roof span allowed 12m. Available in cee or zee shape red oxide primed or galvanized 16 14 or 12 gauge sizes from 4 up to 12 flange widths of 1 1 2 up to 4 cut to your specified lengths hole punching available load tables available for all material. All spans to have 1 row of bridging.

Spacing is typically 24 on center in low snow loads and is reduced based upon truss span and snow load. The cos of the purlin spacing is because the load on the purlins is vertical and the purlin spacing is with the run of the roof. To identify whether yours is the earlier or the latter type look for the end of the rails and check whether the shapes mimics the shape of letter c or letter z. The purlin are ultimately used to fasten the roof steel providing a diaphragm effect along with the siding when properly engineered and installed.

Steel roof purlins and wall girts are produced and available in house. For sake of discussion we will assume a minimal roof snow load of 20 psf pounds per square foot and a 4 12 roof slope. Engineered purlin metal mart offers a complete line of engineered purlin material. Steel z purlins and z girts are also available with other depths and flange widths.

Safe roof purlins spans. Contact flexospan for information on custom purlin and girt structural steel dimensions. The topic we want to discuss today is the purlin installation. Purlins near roof edges or changes of roof slope are subject to higher wind forces than interior purlins.

Purlins are non pressure treated 1 x 4 x 12 lumber that is installed on to the roof in a specific layout pattern and screw pattern. Cpe 0 9 and cpi 0 2. These tables are for spans in which purlins are lapped over each support where the lap length is 15 of the span. Continuous purlin span are simply supported at each end and at a series of equally spaced intermediate supports.

Tables are given for 5 or more spans.