Graphical Construction Glossary >> Roofs and roofing. >> Roof Framing >> purlin cleat

Steel purlin cleat
A MS plate or angle punched to a set pattern of holes or slots to suit a particular size of steel purlins. Either welded or bolted to the support member.
Timber cleat
A short piece of timber fixed to a support member to hold timber purlins in position.

steel purlin cleats
Galvanized steel roof framing showing steel cleats for fixing purlins to the support beams.

Steel purlins are punched to very specific locations, and these details are provided by the manufacture. Be aware that these positions can vary from manufacturer to manufacturer, and even from State to State with the same Manufacturer. Follow the purlin manufacturer's guidelines for cleat dimensions and hole centers.

Steel purlins are punched with horizontal slots (elongated circular holes) to give tolerance for fixing and steelwork fabricators can do the same when making the cleat.

These steel cleats are invariably MS flats with complete 6mm fillet welds to the supports. Mostly in kit type construction are the formed out of angle steel and bolted to both members, as an aid in mass production.

purlin cleats, timber

mortise and tennon joint

You may be forgiven for thinking that the cleats in the sketch above are plain blocks just nailed on. Not so, for the most part like the rest of the truss what appears on the outside to be a simple joint is in fact a well designed and structurally sound mortise and tenon joint.

For fixing timber to timber in today's cost effective world, the ubiquitous pressed metal nail clips or straps are used instead of these timber cleats.

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Please Note! The information on this site is offered as a guide only!  When we are talking about areas where building regulations or safety regulations could exist,the information here could be wrong for your area.  It could be out of date!  Regulations breed faster than rabbits!
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