What is Laminated Veneer Lumber (LVL)?

Laminated Veneer Lumber (also known as peeled and glued wood, Laminated Veneer Lumber, LVL for short) originated in North America in the 1970s and has since been widely used in North America and Europe. LVL is an engineered wood product made by laminating veneers of a certain thickness (3~6 mm) along a certain grain direction and hot-pressing and gluing them with a weather-resistant adhesive.

Europe divides LVL into two types, LVL-P and LVL-C, based on the way the veneers are assembled. Among them, the veneers of LVL-P are all assembled along the grain, while about 20% of the veneers in LVL-C are assembled transversely. Unless otherwise specified, LVL generally refers to LVL-P. LVL-C is an orthogonally glued panel product. Its along-grain strength and stiffness are lower than those of LVL-P, but because some of the veneers are assembled transversely, it also has certain transverse strength, stiffness, connection ductility and dimensional stability. Compared with cross-laminated timber (CLT) and glulam, the size of LVL is not limited by the size of raw materials, and small-diameter and short-length timber can be fully and efficiently used to meet the strength and stiffness requirements of the structure. Compared with solid wood, the natural defects of wood can be effectively removed during the production process of LVL, and it has the advantages of uniform material, high strength, and good dimensional stability, which can meet the construction requirements of engineering fields such as wood structures and bridges. In addition, LVL has a high degree of prefabrication and is easy to drill, cut, and install. It can be used in modern prefabricated wood structures. At present, LVL has been widely used in wood structure walls, floors (roofs), etc. abroad. It can also be used as lvl beams and columns in beam-column structures. In some cases, it is also used as rafters, purlins, joists, lintels, etc. Due to the particularity of its assembly structure, LVL-C is used in elevator shafts, load-bearing walls, floor panels, etc. in multi-story wood structures, which have high strength and stiffness requirements. Domestic LVL often uses fast-growing wood from artificial forests such as poplar and fir as raw materials. Its raw materials have the disadvantages of soft material, low strength, and poor dimensional stability. However, LVL produced from small-diameter fast-growing wood can be effectively used as building structural materials, realizing the use of inferior materials and small materials. It is also of great significance to alleviate the current situation of forest resource scarcity and wood shortage in my country.

As an engineering wood product, the production cost of LVL is higher than that of sawn wood, but because of its good physical and mechanical properties, it can not only efficiently use fast-growing wood, small-diameter wood and short wood, but also the cross-sectional size of LVL components can be smaller than that of sawn wood components under the same structural mechanical performance requirements. At present, domestic LVL is mainly used in non-structural application fields such as furniture and packaging, while there are few related research and applications in civil engineering, and basic theory and experimental data are relatively lacking.

LVL classification Laminated veneer lumber (LVL) can be divided into the following two categories according to its use:

(1) Non-structural laminated veneer lumber Non-structural laminated veneer lumber can be used for furniture manufacturing and interior decoration, such as making wooden products, partition walls, doors, door frames, interior partitions, etc., and is suitable for indoor dry environments.

(2) Structural laminated veneer lumber Structural laminated veneer lumber can be used to make structural components that bear loads instantly or for a long time, such as beams or columns of large-span building facilities, load-bearing structural components of wooden houses, vehicles, ships, bridges, etc., and has good structural stability and durability. It is usually treated with anti-corrosion, insect-proof and flame-retardant treatments according to different uses.

LVL characteristics

Laminated veneer lumber (LVL) has the characteristics of light weight, high strength, stable mechanical properties, and flexible size specifications. It is a new type of high-performance, ecological and environmentally friendly building composite material.

(1) Strength

The strength-to-weight ratio of laminated veneer lumber is better than that of steel. Because the natural defects such as knots, wormholes, cross holes, cracks and diagonal lines that are common in sawn timber are randomly distributed between veneers, it has the characteristics of uniform strength and small coefficient of variation, high allowable design stress and good dimensional stability.

(2) Specifications

Veneer laminated lumber is a new type of structural board. Due to its special production method, its size is not limited by the size of the log or the specifications of the veneer. The width size can be adjusted arbitrarily without restriction. The specification size range is wide, so it can meet the needs of large-span beams, vehicles and ships.

(3) Dimensions

Stability

Veneer laminated lumber has uniform strength, stable dimensions and good durability.

(4) Flame retardancy

Due to the timeliness of the wood pyrolysis process and the glued structure of veneer laminated lumber, veneer laminated lumber as a structural material has better fire safety than steel. The fire test conducted by Japan on American wooden houses showed that its fire resistance was not less than 2h, while the lighter steel structure would lose its support capacity within 1h after being exposed to fire.

(5) Economical efficiency

The economic efficiency of LVL is reflected in the value-added effect of using small materials for large purposes and inferior materials for high-quality purposes. It can be produced using small-diameter wood, bent wood, and short logs, and the yield rate can reach 60%~70%. LVL can be assembled into single boards according to the purpose of wood products, and the single boards can also be easily processed to make the wood products have anti-corrosion, insect-proof, and fire-proof properties. The disadvantage is that the cost of wood products depends on the type and amount of adhesive.

LVL application

Due to its unique advantages in specifications, strength, performance, etc., LVL has a very wide range of applications. According to its use, it can be divided into non-structural and structural uses. Among them, structural LVL is divided into small-size structural materials and large-size structural materials.

Non-structural LVL is mainly used in furniture manufacturing, as the core material or frame of high-end furniture tabletops; small-sized structural materials are mainly used as door and window frames, internal wall pillars and door and window frames, stairs and other building components; large-sized structural materials can be widely used in building joists, roof trusses, I-beams and other components, roofs of family houses, structural frames and floor systems, and can also be used as vehicle and ship materials, sleepers, etc.