Shed Roof Purlin

Safe roof purlins spans.

Shed roof purlin.

The purpose of purlins. And also are a target for thieves once installed. Here is the formula for calculation of a roof purlin. Most sheds with overhangs incorporate both rakes and eaves into their design to give the shed a balanced look.

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. This design is a lot stronger and more robust way of making a steel shed. The purlin are ultimately used to fasten the roof steel providing a diaphragm effect along with the siding when properly engineered and installed. Building trusses on site is easily done for a shed.

Purlins are an important component in a pre engineered steel structural kit. Cleated or bracketed fixing only no flange bolting. Purlins and girts are used longitudinally to support the roof sheeting which they were originally designed for. These structural supports run perpendicular across the rafter beams.

Snap a chalk line horizontally across the roof two feet down from the top. The most common metal shed roofing material is thin steel sheet that is galvanised profiled and painted. The safe spans below are suitable for sheds and class 1 structures with the following assumptions. An eave is created by extending the slope of your roof beyond the walls of your shed.

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. 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. A rake overhang is created by extending the roof beyond the gables of your shed. An eave overhang is located on the longer sides of the shed.

Max roof span allowed 12m. High pressure zones kl 1 5 and 2 0 included. Also known as sheeting rails purlins create the roofing members of the secondary framing of a steel building. 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.

Fasten the purlin with 16d common nails into each vertical rafter. All spans to have 1 row of bridging. Insert two equally spaced nails into the rafter. Lay the first purlin at the ridge of the roof down to the chalk line beginning at either corner.

Spacing is typically 24 on center in low snow loads and is reduced based upon truss span and snow load. Other metals are used in roofing such as zinc copper and lead which i m only going to mention these in passing.