LVL - Beams and veneer panels for the construction of wooden houses and structures

LVL - Laminated Veneer Lamber - is a wood building material in the same category as glulam (glued laminated timber) and CLT (cross laminated timber). Concern for the protection of wood resources and their rational exploitation has led to the emergence of materials that tend to replace more and more solid wood in construction. wooden houses. On the other hand, the issues of carbon emissions, the need to use products with the lowest possible carbon footprint, are driving us towards building materials manufactured with the lowest possible emissions. As a result, materials such as reinforced concrete, steel and even brick are increasingly being replaced by this industrialised wood, which in many cases has superior properties to traditional materials.

What is LVL

The English name - laminated veneer lamber - can be translated as laminated veneer lumber. That is, construction timber - panels, beams, support posts - made from veneer sheets laid one on top of the other along the grain and glued together. The difference with tackleThe main feature of this material, with which we are quite familiar, is that the veneer sheets are laid not perpendicular to each other but in the same direction. Another difference is that the number of veneer sheets can be odd without the risk of a warping panel.

Unlike plywood, which appeared at the beginning of the 20th century, LVL emerged in the second half of the 20th century with the advent of advanced woodworking technologies and the need for rational timber harvesting. This involved the use of qualitatively inferior, lesser-used species and much smaller timber.

There is no uniform idea of the first appearance of the material. Some sources say the term was first used by Wayerhauser - an American company - in the 1960s, when it manufactured LVL by pressing veneers. Others say that LVL came after OSB and cites as its inventor Arthur Troutner, also from the US, who in 1971 built a house using only LVL to demonstrate the material's qualities. In the US, however, the material was first mentioned in the National Design Specifications - the document governing the construction of wooden houses - in 1991.

How to get LVL

To obtain the LVL panels, the logs are first cut to size and peeled. No particular species is specified, but the species found in the greatest quantity in the region is used. Mostly resinous, and while in northern Europe (Finland, Russia) pine is used, in the USA it is used spruce or fir.

Before the veneer is cut by peeling, the logs are kept in hot water for 24 hours to increase the elasticity of the wood, and the veneer not to break when cutting. Then they go to the peeling where the veneer is cut to a thickness of up to 3 mm. Unrolling is used to obtain a long sheet of veneer that can be cut to sizes of up to 1.4 m. The veneer sheets have defects removed and are then dried to a moisture content of 8-10%.

After drying, the veneer is straightened by cutting the edges, sprayed with glue and placed on the platen of a continuous, hot-pressed press, where it is laid sheet on sheet with a gap of a few cm. A continuous panel will then emerge from the press, which is then cut to size. To understand how the veneers are laid to make the continuous panel watch the video below.

During production the wood can be treated against moisture, insect infestation or mould, depending on the requirements and the required quality level.

Main properties

The material obtained by pressing veneers has a lot of qualities that make it a very good building material. Here are some of the qualities of LVL:

• elasticity - the arrangement of the veneers in the same direction allows to obtain a material with high elasticity. For example, the modulus of elasticity of LVL is 24% higher than that of spruce;
• resistant to bending - it is twice as strong as spruce;
• homogeneous - as it is made from many wood boards stacked on top of each other and defects are eliminated, the final product has equal properties over the whole surface of the board, unlike solid wood;
• stability - it is a much more stable material than solid wood, as water absorption is much reduced making dimensional variation non-existent;
• better fire resistance than solid wood - being a material that has successive layers of wood and adhesive it burns more slowly (phenol-formaldehyde or phenol-resorcinol adhesives do not burn). In addition, the high density decreases the air content inside, which slows the spread of fire;
• better resistance to salt air, water vapour, ammonia than concrete or steel. This is why it is used in buildings housing swimming pools, swimming pools or animal farms;
• has the same strength at a much lower weight compared to concrete. This makes it possible to build strong constructions on a smaller foundation and makes installation quicker and easier;
• is a good insulating material and allows the production of prefabricated elements containing insulation material. It is widely used in Western Europe and in the USA to make passive houses and those energy efficient.

Like any material, it must have its drawbacks. Firstly, it is not recommended for outdoor use. There are manufacturers who say that their products have very good moisture resistance due to treatments during production, but I have not found many recommendations for unprotected outdoor construction.

LVL panels without special treatments should not be placed directly on the ground because they absorb moisture over time and can be attacked by insects.

Types of LVL

LVL can be in the form of panels or beams. The method of production is the same for both. The resulting panel can then be cut as a beam or a column.

There are types of LVL, called Q or T, which also have veneers placed perpendicular to each other. The number of parallel veneers along the fibre is much higher than the number of perpendicular veneers. Such products are much stiffer, as the presence of perpendicular veneers prevents the panel from twisting or bending.

What it is used for

LVL is mainly used as a building material. Although it is almost unknown in our country, it is widely used in Western European countries and in the USA for both civil and industrial construction. It can be used in both new and renovated construction.

Being strong and dimensionally stable it is used for:

• load-bearing walls
• floors
• roofing elements
• beams and columns for wooden structures
• achievement prefabricated walls
• elements for doors and windows
• stairs and steps

LVL panels or beams can be made so that the visible face is formed from the ends of the veneers. It's a sort of "end grain" look, but being veneers they look like thicker parallel lines, horizontal or vertical.

Being easy to process, it allows for special design constructions. Below is an example of an office building in Boston using LVL as wood. The top-floor layout is quite spectacular.

Comparison with glulam and CLT

If you've read our articles on glulam and CLT you're probably wondering what the difference is between them and why you should choose one or the other.

The glulam is similar in the way it is made. The laying of the layers of wood is also parallel to the fibre, but with LVL it is 3 mm veneer and with glulam 30-35 mm timber. They are both elastic, but LVL accepts more pressure without the risk of warping.

Compared to CLT, they differ both in the way the layers are laid out - in CLT they are laid perpendicular, as in plywood - and in their size. It is not veneer but timber, like glulam. CLT panels are very strong and stable over time and can also be used in tall timber constructions. But they are heavier and stiffer.

There are factories in Romania that have been producing glulam for years now. In the meantime I understand that some also manufacture CLT. I have not yet heard of a LVL manufacturer in the country, but I found the product in the Holver showroom in Bucharest.

I hope I have managed to come up with new and useful information, and if you think it might be helpful to others you can share it. If you have any questions, queries or additional information on the topic please leave them below in the comments.