Purlins Roof Design

The type and spacing of purlins is a design consideration which depends upon the incident roof loads as well as the limiting lengths of sheeting to be used.

Purlins roof design.

The plane surface of c purlin on its one side has made it a preferred material for cladding due to its easy installation on concrete structures or steel. Purlins are 2 by 4 feet and are installed much like metal roofing. The shape of cee purlins does not allow end lapping they are butted together. How to design c purlins and sag rods design according to nscp 2015 c purlinsare horizontal type steel section that are used to support the load from the roof deck or the sheathing.

The designis based on the maximum yeild strength mn fysx as stated in the aisc manual 13th ed. Designing of roof trusses as per is 800 and is 875 part 1 2 and 3. Purpose use cee purlins are secondary steel framing members most commonly used as roof purlins wall girts and header jamb and sill for windows and doors on metal buildings. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top.

Stratco purlins and girts are used to support roof and wall sheeting in industrial commercial and rural buildings and as structural framing in medium sized buildings and relocatable accommodation as well as garages patios and carports. The roof support system is a ridgepole and either rafters which run perpendicular from the top of the walls to the ridge or purlins which run parallel to the ridge. In structural steel or aluminum construction purlins usually w shapes or channels transfer roof loads to the major structural elements supporting the roof. Various types of roof trusses include king post truss scissor truss north light truss etc.

In timber construction purlins are nailed to the rafter or supporting trusses while in steel roof construction they are welded or bolted to the rafters or trusses by the means of cleats. Maximum span is 11 4m. Description this spreadsheet is to be used to check the adequacy of roof purlins for a specified combination of loads. They give added support to the roof and also provide a nailing surface for the end panels and drip edge.

Welded together they can be used as columns braces and ties. Metal roof purlins are installed horizontally under metal roofs. This spread sheet can only be used for load combinations with two variables. Butted purlins can be used over supports or within the depth of the supporting section.

Details are on page 32.