Laminated veneer lumber
Laminated veneer lumber (LVL) is an engineered wood product that uses multiple layers of thin wood assembled with adhesives. It is typically used for headers, beams, rimboard, and edge-forming material.
LVL offers several advantages over typical milled lumber: Made in a factory under controlled specifications, it is stronger, straighter, and more uniform. Due to its composite nature, it is much less likely than conventional lumber to warp, twist, bow, or shrink. LVL is a type of structural composite lumber,
comparable to glued laminated timber (glulam) but with a higher allowable stress.
Quality
Laminated veneer lumber is similar in appearance to plywood, although in plywood the veneers switch direction while stacking and in LVL the veneers all stack in the same direction. In LVL, the direction of the wood grain is always parallel to the length of the billet. The stacking of these veneers into
a complete board, called a billet, creates a single piece of LVL sharing a common direction of wood grain. LVL is typically rated by the manufacturer
for elastic modulus and allowable bending stress. Common elastic moduli are 12 GPa (1,700,000 psi); 13 GPa (1,900,000 psi); and 14 GPa (2,000,000 psi); and common allowable bending stress values are 19 MPa (2,800 psi); and 21 MPa (3,000 psi). Although the creation of LVL is often proprietary and thus its make up is largely dependent on individual manufacturers, in general one cubic meter of North American lumber is composed of 97.54% wood, 2.41% of phenol formaldehyde resin, 0.02% of phenol-resorcinol-formaldehyde resin, and 0.03% fillers.
Use
Because it is specifically sized to be compatible with I-joist floor framing, residential builders and building designers like the combination of I joist
and LVL floor and roof assemblies.
LVL is considered to be a highly reliable building material that provides many of the same attributes associated with large sized timbers. LVL can also be used in combination with gluelam as an outer gluelam tension lam to increase the strength of the gluelam beam. However, due to the fact that the assembly adhesives limit the penetration of chemicals typically used to treat outdoor-rated lumber, LVL may not be suitable for outdoor load-bearing use.
A deck built using pressure-treated LVL collapsed due to internal rotting of the twelve-year-old LVL components, although the LVL beams had passed
regular visual inspections.The breakdown of LVL end uses in North America is 33% new single family residential construction, 25% residential
renovations and upkeep, 8% new non-residential construction and 34% manufacturing furniture and other products.
Manufacturing
LVL is commonly manufactured in North America by companies that also manufacture I-joists. LVL is manufactured to sizes compatible with the depth of I-joist framing members for use as beams and headers.
Additionally, some manufacturers further cut LVL into sizes for use as chord-members on I-joists.
In 2012, North American LVL manufacturers produced more than 1.2 million cubic metres (43.4 million cubic feet) of LVL in 18 different facilities,
and in 2013 the production increased with more than 14%. It is not coincidental that LVL mills are often co-located with I-joist
manufacturing facilities as many builders use a combination of I-joists and LVL in floor and roof assemblies.
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