Types of Long Span Timber Beams Print E-mail
Only a specific range of engineered timber beams are large enough and strong enough to carry the loads involved in long span situations. The main options to suit the typical 4 to 8m span situations (See: Typical Long Span Beam Situations ) include:










Plywood Box Beams
These beams involve plywood sheets nailed to horizontal flanges and vertical stiffeners. The assembly looks similar to a stud frame. Features include:
  • Suitable for medium to long spans
  • Lightweight
  • Span increases with beam depth
  • Beams can be used to double as wall construction (subject to the exclusion of door and similar openings)
  • Can be built onsite or prefabricated offsite
Laminated Veneer Lumber beams (LVL)
These beams involve thin sheets of timber laminated together to form a solid section. The process serves to minimise weaknesses in the timber thus providing higher strength. Features include:
  • Deep standard size sections available
  • Many applications possible including short to long spans
  • Some LVL products are customised to suit specific beam applications e.g. strutting beams
Glued Laminated Timber Beams
These beams involve pieces of sawn timber glued together to form solid timber sections. Like LVL, the process serves to minimise weaknesses in the timber thus providing higher strength. Features include:
  • Standard or customised sizes possible
  • Suitable for mid to long spans
  • Many shape configurations possible
  • Well suited to decorative portal frame applications
Glued "finger joints" are often used to give continuity to the laminations. The geometry of the finger joints enables a large surface area of glue to transmit the force across the discontinuity at the end of one portion of the lamination to the next portion. The shallow angle of the finger joints means that the glue transmits load in shear across the glue line. This is much more effective than direct tension across a glued butt joint. Good quality glued finger joints give performance that is comparable with the design tension strength of the lamination material.

It is possible to manufacture a glulam beam with higher strength laminates in areas of high stress such as in the top or bottom of beams, and lower strength laminates in the areas of low stress.
Other Engineered Beam Options
Companies that specialise in nail plated timber trusses and similar components have a variety of beam options that involve specific design characteristics
  • Usually limited to short to mid span scenarios (e.g. double garage door openings) and limited load width
  • Lightweight
  • Are designed to be fabricated offsite (e.g. with frames and trusses)
 
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