If you work in the construction industry, you've likely heard mention lately of CLT and glue-laminated timber. Just recently, CLT was indicated as the cause of a flooring failure at a new, $800 million building on the Oregon State University campus in Corvallis, Oregon. Fortunately, no one was injured when the flooring gave out, but the incident did raise questions about CLT and glulam and whether they have a place in public, commercial and residential construction. Let's start answering that question by defining just what CLT and glulam are.
What is CLT?
CLT, short for cross-laminated timber, is wood produced by gluing multiple panels of sawn wood together with moisture-resistant structural adhesives. With CLT, each piece of wood is placed perpendicularly to the piece of wood next to it. Although CLT is similar to plywood, it uses thicker pieces of timber in its construction and is, thus, better suited for structural support beams. Both CLT and glulam are extremely versatile and can be used in walls, roofings, flooring and ceilings. The thickness of these products can be modified by adding more or fewer layers.
What is Glue-Laminated Timber?
Glue-laminated timber, often referred to as glulam, differs from CLT in that the pieces of wood are all set in the same direction (the grain lines all go the same way). Like CLT, this type of engineered lumber has a number of construction applications. Glulam is often used to make curved beams and supports, since its multi-piece construction allows it to be "shaped" without losing its structural integrity.
Benefits of using CLT and glulam in construction
Both CLT and glulam off a number of benefits when used in residential, commercial and public construction projects. Just a few of these are highlighted below:
1. Strength. The cross pattern of CLT gives these engineered wooden panels much greater strength than each piece of lumber would have on its own. While a single board is vulnerable at the grain lines, CLT has no single grain line that runs through the entire panel. Even glulam is inherently stronger than traditional lumber since it adds multiple layers.
2. Environmentally friendly. Since no fossil fuels are used in the construction of CLT and glulam, these products are considered to be "green" and sustainable. It is generally made from smaller, second growth trees, and doesn't deplete old growth forests.
3. Fire resistant. CLT and glulam char rather than burn when exposed to flame. Even charred, these materials retain up to 90 percent of their structural integrity, according to a recent study.
4. Prefabrication. CLT and glulam are put together by the manufacturer and shipped to the job site, saving precious time over walls and sub-floors that have to be put together onsite.
5. Insulation properties. CLT and glulam also help with insulating the building. The more layers to the product, the higher the thermal insulation value.
6. Weight. CLT and glulam are relatively lightweight compared to other building materials, such as concrete. This is especially valuable in the construction of high rise structures.
While CLT and glulam have been somewhat controversial recently, these products offer a myriad of benefits for construction firms, not the least of which is saving money and time by being put together off site. If you are in the planning stages of a new project, consider adding these products to your construction plans.
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