Sep. 26, 2022
First used during World War II to make airplane propellers, laminated veneer lumber (LVL) has been available as a construction product since the mid-1970s. LVL is the most widely used structural composite lumber (SCL) product and provides attributes such as high strength, high stiffness and dimensional stability. The manufacturing process of LVL enables large members to be made from relatively small trees, providing efficient utilization of forest resources. LVL is commonly fabricated using wood species such as Douglas fir, Southern yellow pine and Poplar.
LVL is used primarily as structural framing for residential and commercial construction. Common applications of LVL in construction include headers and LVL beams, hip and valley rafters, scaffold planking, and the flange material for prefabricated wood I-joists. LVL can also been used in roadway sign posts and as truck bed decking.
LVL slat is made of dried and graded wood veneer which is coated with a waterproof phenol-formaldehyde resin adhesive, assembled in an arranged pattern, and formed into billets by curing in a heated press. The LVL billet is then sawn to desired dimensions depending on the end use application.
The grain of each layer of veneer runs in the same (long) direction with the result that LVL is able to be loaded on its short edge (strong axis) as a beam or on its wide face (weak axis) as a plank. This type of lamination is called parallel-lamination and produces a material with greater uniformity and predictability than engineered wood products fabricated using cross-lamination, such as plywood.
LVL is a solid, highly predictable, uniform lumber product due to the fact that natural defects such as knots, slope of grain and splits have been dispersed throughout the material or have been removed altogether during the manufacturing process.
The most common thickness of LVL is 45 mm (1-3/4 in), from which wider beams can be easily constructed by fastening multiple LVL plies together on site. LVL can also be manufactured in thicknesses from 19 mm (3/4 in) to 178 mm (7 in). Commonly used LVL beam depths are 241 mm (9-1/2 in), 302 mm (11-7/8 in), 356 mm (14 in), 406 mm (16 in), 476 mm (18-3/4 in) and 606 mm (23-7/8 in). Other widths and depths might also be available from specific manufacturers. LVL is available in lengths up to 24.4 m (80 ft), while more common lengths are 14.6 m (48 ft), 17 m (56 ft), 18.3 m (60 ft) and 20.1 m (66 ft). Timber beam LVL can easily be cut to length at the jobsite.
All special cutting, notching or drilling should be done in accordance with manufacturer’s recommendations. LVL is a wood-based product with similar fire performance to a comparably sized solid sawn lumber or glued-laminated beam. Manufacturer’s catalogues and evaluation reports are the primary sources of information for design, typical installation details and performance characteristics.
LVL is mainly used as a structural element, most often in concealed spaces where appearance is not important. Finished or architectural grade appearance is available from some manufacturers, usually at an additional cost. However, when it is desired to use LVL in applications where appearance is important, common wood finishing techniques can be used to accent grain and to protect the wood surface. In finished appearance, LVL resembles plywood or lumber on the wide face.
The distance an LVL beam can span depends on its width and depth. Laminated veneer lumber typically comes in 1-3/4”, 3-1/2”, 5-1/4”, and 7” widths or thicknesses, and depths of 5-1/2” to 24”, including standard and nonstandard depths. The lengths commonly range from 4’ to 48’, usually available in 4’ increments. Plus, special orders between up to 60’ or 80’ are available – depending on the manufacturer.
Most building suppliers will carry 8’, 12’, and 16’ lengths and order in longer lengths as required. The length often depends on the manufacturer, with 80’ being available but 60’ or less are more common due to transportation restraints. Formwork LVL beams can be cut to length and notched or drilled at the building site, and double, triple, or quadruple ply is used for strength, the same as dimensional lumber, making it a versatile choice.
The depth of the beam along with its width, combined with common construction variables such as building width, loads, number of stories, joist spacing, etc., determine its span. Whether the span is multiple or a single is also important. As is how it will be used – floor beam, joist, rafter, ridge beam, header, or lintel.
The structural design variables for the beam are vital and vary with the manufacturer. This means trying to compare different products is often difficult, so always check with your local building department or a Structural Engineer. Additionally, if holes need to be drilled through an LVL wood beam, it is recommended that the beam be 3-1/2” or wider.
A 1-3/4” 2.1E 2800 beam with 100% load duration that is 7-1/4” deep will span up to 16’, an 9-1/2” deep will span to 20’, and 11-7/8” deep to 26’. A 14”, 16”, and 18” deep will all span 30’, but 16” and 18” are typically doubled or tripled for greater loads. 3-1/2” 2.1E 3100 at 7-1/4” deep will span 20’, a 9-1/2” up to 26’, and other depths 30’. A 7” 2.1E 3100 at 24” deep can potentially span up to 60’ depending on load and construction variables, and application.
Structural LVL beams are used for a variety of structural framing and construction purposes, including floor and ridge beams, joists, headers, lintels, rafters, trusses, rim boards, and scaffold planks. Laminated lumber is also used for road signposts, ramps, flange wood for I-joists, and even truck bed decking and skateboards, as well as numerous other uses. Most LVL lumber is for dry interior use, but H3 and other chemically treated laminated lumber can be used outdoors and exposed to various weather conditions.
Installing an LVL beam depends upon whether the installation is part of a new build or a renovation. A new build install is much like using standard lumber. The beam is typically supported at each end on exterior walls and may have one or more support posts along its span.
The depth and width, as well as the length, contribute to the weight and may require a crane to lift it into place. The beam may be composed of two or more widths or plies of LVL for lighter lifting, or a solid width up to 7”. Once in place, the beam is leveled and braced, awaiting joist placement.
Removing drywall or lathe and plaster, rearranging plumbing, electrical, and HVAC are often necessary. It commonly requires one or two temporary “walls” to support the ceiling or floor structure while support posts are placed or king studs installed, and the new beam measured, cut, and lifted into place.
The length of the beam may require opening a section of the exterior wall to allow passage into the location too. Once installed and secured, the temporary “walls” are removed. Using 1-3/4” wide LVL beams is lighter than wider beams, and placing and bolting two or more together provides the same structural support as a wider beam.
The distance an LVL beam can span depends on a plethora of factors. Some manufacturers limit their beams to 60' due to transportation issues, while others have the capability to manufacture beams up to 80’ long. So, the longest unsupported span possible using LVL would be 80-feet.
Typically, though, it is common for a continuous LVL span to be between 20' and 30'. Hopefully, you have a better understanding of what LVL beams are and how they may be used on your next project.
