Shed Roof Purlin

Snap a chalk line horizontally across the roof two feet down from the top.

Shed roof purlin.

These structural supports run perpendicular across the rafter beams. A rake overhang is created by extending the roof beyond the gables of your shed. Fasten the purlin with 16d common nails into each vertical rafter. Cleated or bracketed fixing only no flange bolting.

All spans to have 1 row of bridging. Also known as sheeting rails purlins create the roofing members of the secondary framing of a steel building. The most common metal shed roofing material is thin steel sheet that is galvanised profiled and painted. High pressure zones kl 1 5 and 2 0 included.

Cos of live load dead load x cos of the purlin spacing x purlin span squared 8 x sm section modulus of the member x duration of load 1 15 in areas with snowfall x cr repetitive member factor of 1 15 where members are 24 on center or less fb fiberstress required. The purpose of purlins. Lay the first purlin at the ridge of the roof down to the chalk line beginning at either corner. Purlin roof structure civil engineering design in architecture or structural engineering or building a purlin or purline is a horizontal structural member in a roof.

Purlins and girts are used longitudinally to support the roof sheeting which they were originally designed for. The purlin are ultimately used to fasten the roof steel providing a diaphragm effect along with the siding when properly engineered and installed. In a structural steel shed the main portal frames and roof rafters are made from strong steel sections which are welded together and later bolted together. Building trusses on site is easily done for a shed.

This design is a lot stronger and more robust way of making a steel shed. 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. The safe spans below are suitable for sheds and class 1 structures with the following assumptions. Most sheds with overhangs incorporate both rakes and eaves into their design to give the shed a balanced look.

A simple gable shed roof is often built using 2 4 or 2 6 lumber for the rafters and 2 4 for the collar ties. Cpe 0 9 and cpi 0 2. An eave is created by extending the slope of your roof beyond the walls of your shed. The rafters are angle cut at the ridge end and notched with a birdsmouth where it meets the top plate of the supporting wall.

Here is the formula for calculation of a roof purlin. Spacing is typically 24 on center in low snow loads and is reduced based upon truss span and snow load. Max roof span allowed 12m. Safe roof purlins spans.

And also are a target for thieves once installed. Insert two equally spaced nails into the rafter.