Glued-Laminated Timber (GLT) Design + Construction


What is Glulam?

Glued-laminated timber (glulam) is a structural engineered wood product commonly used for beams and columns in residential and commercial applications. It is a highly visible form of mass timber in contemporary projects, with long spans framing signature designs left exposed to take advantage of wood’s natural aesthetic.

Illustration of Glulam

How It Works

To form a glulam component, wood laminations (dimensional lumber) are positioned according to their stress-rated performance characteristics. In most cases, the strongest laminations sandwich the beam to absorb stress proportionally and ensure longevity. The laminations are jointed end to end, allowing for long spans, and are bonded with a durable, moisture-resistant adhesive. The laminations’ grains run parallel with the member’s length to improve its strength.

Glulam members come in standard and custom sizes. Depths range from 6 inches to 72 inches, and widths range from 2.5 inches to 10.75 inches, according to APA. Components are cut to length when ordered and can surpass 100 feet. Commercial projects often require longer spans and accommodate bigger loads than residential projects, meaning custom widths and depths are often required. In addition to straight spans, glulam can also be used for curved and pitched applications.

How It's Used

Glulam has a reputation for being used in exposed applications such as vaulted ceilings and designs with large open spaces. With four appearance grades—framing, industrial, architectural, and premium—glulam is used when you seek a combination of structural and aesthetic attributes. This includes a range of architectural applications, including churches, higher education facilities, offices, and homes.

Glulam can work behind the scenes, too, as trusses, purlins, floor beams, cantilevers, and other necessary structural elements. Glulam has found use as floor and roof decking planks as well. 

Strength for long spans.

Glulam is stronger than steel at comparable weights. According to APA — the Engineered Wood Association.

That makes glulam a cost-effective choice for long, structural spans and tall columns with minimal need for additional support.

Glulam mass timber beam

Case in Point

Bullitt Center

For its design of the Bullitt Center—a six-story office building in downtown Seattle—local architecture firm The Miller Hull Partnership picked mass timber, specifically glulam, over concrete for the structural frame.

The material choice proved beneficial for this Living Building Challenge-certified structure due to its low carbon footprint and sustainable, local sourcing.

Bullitt Center exterior street view

Download the 2022 Mass Timber Manual.

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