Roof Purlin Deflection

Deflection is the bending or sag caused by loading.

Roof purlin deflection.

Butted purlin system butted connection roof sag system roof angle brace system mono pitch roofs steep pitch roofs shallow pitch roofs long roof slopes curved roofs tiled roofs cantilever purlins introduction zed and cee section range overview product range page 1 sections eaves beam details typical connections. An example is air conditioning put on top of a roof this may well minimize wind uplift whilst increasing dead load downwards. In architecture or structural engineering or building a purlin or purline is a horizontal structural member in a roof. If purlins are undersized missing or poorly connected to the party wall to support the rafters it can result in deflection which often has a dipping or bulging appearance to the roof surface.

All structural members will deflect or flex under load. Another clients on the odd occasion suspend ceilings to office complexes from roofing systems designed to have deflection ratios of 1 150 when most office ceilings are designed for around 1 300. The use of purlins as opposed to closely spaced rafters is common in pre engineered metal building systems and both the ancient post and beam and newer pole building timber frame construction methodologies. The amount of flex depends on the magnitude of the load applied span of the member and stiffness of the member.

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. Image copyright belongs to albion sections limited uk roof purlin are members used to directly support roof sheeting materials and could be made of timber or steel.