Shed Roof Purlin

Here is the formula for calculation of a roof purlin.

Shed roof purlin.

Spacing is typically 24 on center in low snow loads and is reduced based upon truss span and snow load. 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. The purpose of purlins. The purlin are ultimately used to fasten the roof steel providing a diaphragm effect along with the siding when properly engineered and installed.

Lay the first purlin at the ridge of the roof down to the chalk line beginning at either corner. This design is a lot stronger and more robust way of making a steel shed. The most common metal shed roofing material is thin steel sheet that is galvanised profiled and painted. 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. Cpe 0 9 and cpi 0 2. A rake overhang is created by extending the roof beyond the gables of your shed. Max roof span allowed 12m.

An eave is created by extending the slope of your roof beyond the walls of your shed. Cleated or bracketed fixing only no flange bolting. All spans to have 1 row of bridging. These structural supports run perpendicular across the rafter beams.

The rafters are angle cut at the ridge end and notched with a birdsmouth where it meets the top plate of the supporting wall. 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. Safe roof purlins spans. An eave overhang is located on the longer sides of the shed.

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. Fasten the purlin with 16d common nails into each vertical rafter. Insert two equally spaced nails into the rafter. Other metals are used in roofing such as zinc copper and lead which i m only going to mention these in passing.

And also are a target for thieves once installed. Purlins are an important component in a pre engineered steel structural kit. The safe spans below are suitable for sheds and class 1 structures with the following assumptions. Building trusses on site is easily done for a shed.

High pressure zones kl 1 5 and 2 0 included. Purlins and girts are used longitudinally to support the roof sheeting which they were originally designed for.