What are cross purlins?
Purlins & Cross Connectors are made of aluminum or steel for long lasting durability. Cross Connectors offer unique aluminum cross connecting system used for purlin to rafter connections, trellis systems for grapes and other vines and shade and wind barrier frames.
Can purlins be used as rafters?
A traditional purlin strictly by definition is a horizontal structural member in a roof. Purlins traditionally support the roof deck / cladding / sheeting and are in turn supported by the principal rafters / steel beams etc. In some instances, either 6″ or 8″ “C” purlins back to back can be used as rafters.
What is the difference between purlins and rafters?
The rafters are the beams of wood angled upward from the ground. They meet at the top of the gable at a ridge beam, which has extra bracing to attach it to the rafters. The purlins are the large beams perpendicular to the rafters; from this shot, it appears that there are three purlins on either side of the roof.
What size purlins do I need?
The sizes are as follows: A four-inch purlin can span 12 feet. A six-inch purlin can span 18 feet. An eight-inch purlin can span 25 feet.
How far apart should roof purlins be?
The purlin are ultimately used to fasten the roof steel providing a diaphragm effect, along with the siding, when properly engineered and installed. Spacing is typically 24″ on center in low snow loads and is reduced based upon truss span and snow load.
How do I support my roof purlins?
Roof purlins are usually supported by 2×4 or 2×6 posts or struts. The posts will be spaced in four-foot distances for 2×4 purlins, while 2×6 purlins have them spaced at six feet apart. If the space between the posts is bigger than eight feet, a brace will be needed to avoid buckling.
How far can purlins overhang?
Beam and rafter overhangs should not exceed 36″, purlins should not exceed 24″.