Other metals are used in roofing such as zinc copper and lead which i m only going to mention these in passing.
Shed roof purlin.
This design is a lot stronger and more robust way of making a steel shed.
Cleated or bracketed fixing only no flange bolting.
Most sheds with overhangs incorporate both rakes and eaves into their design to give the shed a balanced look.
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.
Purlins are an important component in a pre engineered steel structural kit.
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.
The purlin are ultimately used to fasten the roof steel providing a diaphragm effect along with the siding when properly engineered and installed.
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.
The safe spans below are suitable for sheds and class 1 structures with the following assumptions.
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.
Purlins and girts are used longitudinally to support the roof sheeting which they were originally designed for.
Snap a chalk line horizontally across the roof two feet down from the top.
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.
These structural supports run perpendicular across the rafter beams.
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.
Building trusses on site is easily done for a shed.
And also are a target for thieves once installed.
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.
Insert two equally spaced nails into the rafter.
Max roof span allowed 12m.
High pressure zones kl 1 5 and 2 0 included.
Cpe 0 9 and cpi 0 2.
Safe roof purlins spans.
The purpose of purlins.
All spans to have 1 row of bridging.
Fasten the purlin with 16d common nails into each vertical rafter.
Here is the formula for calculation of a roof purlin.
