Laminated Veneer Lumber (LVL)
Laminated Veneer Lumber (LVL) is a high-strength engineered wood product used primarily for structural applications. It is comparable in strength to solid timber, concrete and steel and is manufactured by bonding together rotary peeled or sliced thin wood veneers under heat and pressure. LVL was developed in the 1970s and is today used for permanent structural applications including beams, lintels, purlins, truss chords and formwork. LVL can be used wherever sawn timber is used however one of the main advantages is that it can be manufactured to almost any length, restricted only by transportation to site.
Prior to lamination, the veneers are dried and the grains of each veneer are oriented in the same direction. This makes LVL stronger, straighter and more uniform than solid timber and overcomes some of timber's natural limitations such as strength-reducing knots. This gives orthotropic properties (different mechanical properties against different axes) in a similar way to the properties of sawn timber, rather than the isotropic properties (the same mechanical properties in each direction) in the plane of plywood. The added durability of being an engineered wood product means LVL is less prone to shrinking or warping. LVL can also support heavier loads and span longer distances than normal timber.
Section sizes are then cut from 1200 m wide sheets or "billets". The ability to cut different shapes from the LVL sheets allows for structural innovation using angular and curved shapes.
LVL provides a cost-effective and sustainable building material, delivering high structural reliability and strength.
Note: Some LVL members can be made with a few laminations laid up at right angles to enhance the shear strength of the member. These are known as Cross-Banded LVLs and may need to be specially ordered, as it is not a commonly stocked item.
A truss is a structure comprising one or more triangular units. Each triangle is constructed with straight and usually slender members of timber, connected at the ends by joints. External loads, and the structure's reaction to those loads, act at the joints, resulting in forces that are either tensile or compressive.
The strength of a truss lies in its triangulation of banding members that work together to the advantage of the overall structure. For trusses, compression members often dictate the size of the elements, thus designs that have short compression members or restraint against lateral buckling are generally more efficient than trusses with longer compression members.
Within a building two forms of trusses can be found. Nail plated trusses are trusses hidden from view that use nail plates as connectors. Architectural trusses refer to those attractively detailed timber trusses, exposed to view. This guide focuses primarily on the application process of the latter.
The benefits of timber trusses are notable and numerous. Timber roof trusses are an ecologically sound choice, compared to conventionally pitched roofs, they use smaller dimension timbers that span greater distances and this in turn reduces the total timber volume contained within. Architectural timber trusses are lightweight, enabling speedy and efficient construction and installation that results that in a visual feature to be enjoyed for decades.
This article provides a comprehensive overview to the processes involved in specifying, assembling and installing an architectural roof truss.
Lightweight timber construction typically comprises framed and braced structures to which one or more types of cladding are applied. Framing configurations can range from the closely spaced light timbers commonly seen in stud frame construction to large, more widely spaced timbers. A timber framed building can be placed on a concrete slab or on posts/poles or bearers resting on piers/stumps supported on pad footings.
Used in houses or multi-residential dwellings, lightweight timber construction offers the flexibility of a wide range of cost effective design options.
When the timber comes from sustainable sources, this construction method can be environmentally advantageous as it combines timber's low embodied energy with its capacity to store carbon.
Timber portal frames are one of the most favoured structural applications for commercial and industrial buildings whose functions necessitate long spans and open interiors. As a material choice, timber offers designers simplicity, speed and economy in fabrication and erection.
Timber portal frames offer a strong, sound and superior structure. Structural action is achieved through rigid connections between column and rafter at the knees, and between the individual rafter members at the ridge. These rigid joints are generally constructed using nailed plywood gussets and on occasion, with steel gussets.
From material selection to finishing, this application guide provides a comprehensive overview of the process of using timber in the specification, fabrication and erection of portal frame structures.