What Is Glue-Laminated Wood (Glulam)?
Nov 18, 2020
Short for “glue laminated timber,” glulam is a newly popular addition to the family of engineered wood products with an unusual name. Glulam beams offer a unique combination of beauty and strength. According to APA, the Engineered Wood Association, it’s stronger than steel.
“What’s great about glulam is that you can sand them and bring out all of the grains. You can use more exotic woods and get pretty beams that are actually structurally solid. You’ll see a lot more of this in the future.” -Professional builder Jordan Smith
While glulam has attracted the interest of builders and architects in recent years, it in fact has a long history. The original Swiss patent for this type of engineered wood dates back to 1901 and one of the earliest buildings in the United States using it was a USDA Forest Products Laboratory in Madison, Wisconsin that was completed in 1934—it is still in use today.
An old postcard showing the Forest Products Building, c. 1930. BOSTON PUBLIC LIBRARY/PUBLIC DOMAIN.
How Is Glulam Made?
A glulam beam is, basically, a bundle of lumber pieces, or laminations. The strongest laminations are placed on the outside of the beam, creating a final product that is more durable and better able to absorb any stress placed on it. The different pieces are then joined together with a durable, moisture-resistant adhesive. Because the different laminations are laid end to end, it is possible to create long spans that can bridge large open spaces—an appealing design feature with applications including both commercial and residential projects.
Glulam products made of Douglas fir and southern pine are common, but this structural glue laminated timber product can also be made with a variety of types of wood, including cedar and spruce.
Uses of Glulam
Because of its inherent strength, glulam is often used in public buildings, like churches and performance spaces, where it allows for dramatic open spaces in applications such as vaulted ceilings. Open space designs in residential projects can also use these beams in places where long spans without intermediate supports are required. Though much of the appeal of glulam is that it highlights the beauty of exposed wood, it is also often used in structures where the glulam elements are not visible as with floor beams.
Some prominent buildings constructed with glulam include:
- The Aspen Art Museum by Shigeru Ban
- The BC Passive House Factory by Dürfeld Constructors
- The Gammel Hellerup Gymnasium by BIG (Bjarke Ingels Group)
- Sheffield Winter Garden by Pringle Richards Sharratt Architects and Buro Happold
- The Yusuhara Wooden Bridge Museum by Kengo Kuma and Associates
Pros and Cons of Glulam
Professional builder Jordan Smith predicts that glue-laminated timber and its CLT (cross-laminated timber) cousins will become much more common in the coming years, and there are many advantages to using glulam that are driving its current popularity. Architects and builders should also be aware of some concerns, however.
4 Advantages of Glulam
As an engineered wood product, glulam can be made in a variety of shapes and sizes in response to the structural and design needs of each project. Creating curved arches and other complex shapes is easy with glulam products.
Glulam is more expensive than traditional timber but it is generally cheaper than steel (especially if installation costs are included), the material it would typically replace when it is used to span large open spaces.
3. Green Factor
Because glulam is made from a renewable resource—trees—that are typically locally grown, it is arguably a more environmentally friendly product than other alternatives.
4. Design Considerations
Glulam provides buildings with the warm, inviting look of exposed wood. While steel beams can functionally play the same role in many structures, the beauty of glulam is a large part of its appeal to architects and builders.
3 Disadvantages of Glulam
If an improper adhesive is used, the different laminations in the beam may separate. Improvements in adhesives have vastly reduced the incidents of delamination, but if it is observed before beams are used, you should notify the manufacturer. If you notice delamination in a completed building, a structural engineer should be consulted to provide possible solutions.
2. Other Maintenance Concerns
All wood products, not just glulam, are prone to some common problems: rot, cracks (small openings that run parallel to the grain and which can develop into splits), damage from insects such as termites, and normal moisture fluctuations that occur with wood. The proper application of sealants and attention to ventilation can minimize these risks. Glulam made with preservative-treated wood is another possibility to consider.
Builders are divided on this question, though some are skeptical about the long-term durability of glulam when compared to steel. While glulam has been used for over a century, its new spike in popularity is fairly recent. Whether this type of wood beam will last as long as steel beams in a variety of different structures remains to be seen.
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