Many people associate glulam with striking applications, such as vaulted ceilings and large open spaces with exposed ceilings and beams. In churches, schools, restaurants, lodges, and other commercial buildings, glulam is often specified for its beauty, as well as its long-recognized strength. Glulam has the classic natural wood appearance that holds a timeless appeal.
From a more practical standpoint, glulam is a good choice for many custom and commercial applications because it is a versatile product that can be manufactured with the following features and additional services:
- Curved — glulam beams and arches can be manufactured to meet specific radius requirements as needed for any project
- Custom widths, depths, and lengths to meet virtually any design requirements
- Available in a range of appearance classifications including framing, industrial architectural and premium (special order only)
- Available in a variety of species, including Douglas-fir, Southern Pine, Alaska Cedar, Port Orford Cedar, and Spruce
- Preservative-treated glulam available in both custom and stock beam sizes, but may require special order, depending on member size
- Custom fabrication services available from some manufacturers
Longer Spans Open Design Possibilities
The superior strength of glulam allows longer clear spans than solid-sawn lumber. This opens up the design possibilities in both commercial and residential construction. In commercial design, custom glulam beams can span more than 100 feet. In reticulated glulam framed dome structures, glulam arches span more than 500 feet.
Glulam trusses also take many shapes, including simple pitched trusses, complicated scissors configurations, and long span bowstring trusses with curved upper chords. When designed as space frames, glulam truss systems can create great clear spans for auditoriums, gymnasiums, churches, and other applications requiring large, open-floor areas.
Panelized Roofs Top Large, Open Spaces
In large, commercial buildings, such as warehouses and large retail facilities, glulam beams are an integral component of panelized wood roof systems.
In a typical panelized system, pre-framed units are constructed with glulam purlins or trusses spaced 8 feet on center. Lumber stiffeners spaced 16 inches or 24 inches on center span between the glulam members. Structural wood panels are then attached to the stiffeners and purlins and the entire assembly, 8 x 72 feet or greater, is lifted to the roof elevation with forklifts. This greatly speeds the erection process and minimizes construction costs.
In some panelized roof designs, a cantilevered glulam girder system allows for long-span roofs with minimal need for intermediate columns, thus providing more open column grid spacings. This feature, combined with extra roof height, maximizes both space efficiency and storage versatility.
Designing for Deflection
In longer span applications, deflection is often a controlling design factor. While any wood bending member can be designed to minimize deflection, glulam is the only engineered wood product that can be easily cambered to reduce the aesthetic effect of in-service deflections. Camber is curvature built into a fabricated member which is opposite in direction and magnitude to the calculated deflection which will occur under gravity loads.
The glulam industry recommends that roof beams be cambered for 1-1/2 times the calculated dead load deflection. This will generally be sufficient to assure that the beam will not exhibit a sag over a period of many years of loading, as may occur with non-cambered wood products. To achieve a level profile it is recommended that floor beams only be cambered for 1.0 times the calculated dead load deflection.
Camber for glulam beams is specified as either “inches of camber” or as a radius of curvature that is to be used in the manufacturing process. Commonly used curvature radii for commercial applications are 1600 and 2000 feet, although any camber may be specified.
Because most residential applications require very little or no camber stock beams are often the ideal choice. Stock glulam beams are typically supplied with a relatively flat camber radius of 3,500 feet or zero camber. If more camber is required, custom beams are available through the manufacturers.
Commercial Case Studies
Featured Project: Reveley Nursery Facility at the University of Idaho
The University of Idaho's new Tom & Teita Reveley Nursery Facility is a flexible space that showcases the beauty and versatility of the region's natural wood. Architects from Patano + Hafermann used several common-sense green design principles, like incorporating locally sourced wood products, to create a multi-functional space that respects the vision of the College of Natural Resources: to maximize and preserve Idaho's forest resources.
According to Steven Hacker, Director of development for the College of Natural Resources, "We wanted the building to not only be classrooms for native plant regeneration, forest nursery operations, and forestry education, but also a real-world classroom for visitors to learn about wood from Idaho and the applications of wood as a sustainable and renewable material." The resulting facility serves several different purposes: as a classroom and research center, the sales office for the Franklin H. Pitkin Nursery and as an event space for special functions.
Wood products from Idaho are evident throughout the structure. Elements include: a wood-framed foundation, exposed glulam beams, and a layer of finished wood laminate on the ceiling, as well as handcrafted wood doors, wood-framed windows, and wood flooring made of larch and Douglas-fir from the college's own experimental forest.
Read more in the Reveley Nursery Facility Case Study.
Featured Project: Curved Glulam Beams Bring Sense Of Grandeur to LeMay Museum
When entering the exhibit hall at the LeMay Museum in Tacoma, Washington, visitors may find themselves gazing up at the ceiling as well as taking in the lines of gleaming classic cars. A soaring roof system made with curved glulam beams offers a striking sense of grandeur while simultaneously lending a warm, grounded aesthetic to the vast space.
Nicknamed “America’s Car Museum,” the 165,000-square-foot facility was created to celebrate America’s love affair with the automobile. Across its 4-story, 9-acre campus, the museum houses up to 350 cars, trucks and motorcycles from private owners, corporations, and the expansive Harold LeMay collection, from a 1906 Cadillac Model M to a 1965 Lotus racecar to a 1983 DeLorean DMC 12. Rotating exhibits, such as a collection of glass hood ornaments, also are showcased.
Read more in the LeMay—America's Car Museum Case Study.
Featured Project: Glulam Timber Truss Bridge Spans Remote River
The Placer River Pedestrian Bridge, completed in July 2013, is the longest clear-span glulam timber truss bridge in North America. The 280-foot long camelback bridge is located in Chugach National Forest in Alaska at the Spencer Glacier Whistle Stop, one of five stops planned along a new railway in Alaska’s National Forests and Parks. Designed by Western Wood Structures, the bridge was constructed with preservative-treated Douglas fir glulam trusses, Alaskan Yellow Cedar decking, and steel connectors.
The Placer River Pedestrian Bridge faced unique design challenges. Aesthetically, the US Forest Service wanted the bridge to evoke a look and feel reminiscent of an early 20th century railroad camp. At the same time, the backcountry bridge’s design had to not only withstand extreme weather, but also be placed high enough to avoid collisions with icebergs and ice floes from nearby Spencer Glacier. Sitting 25 feet above the waters of the Placer River, the bridge design meets every requirement for appearance, durability, and strength—and was achieved with cost-effective materials. “People are pleased with the bridge—with the way it looks and with the way it fits in with the setting,” says Rod Dell’Andrea, a structural engineer for the USFS. “It’s truly a context-sensitive design and installation.”
Read more in the Placer River Trail Bridge Case Study.
Featured Project: Glulam Meets Sustainable Building Goals in Bullitt Center
Described as "the greenest commercial building in the world," the Bullitt Center in Seattle, Washington, pushes the envelope in urban sustainability. The six-story, 52,000-square-foot structure is designed to meet the stringent requirements of the Living Building Challenge (LBC), a performance-based certification program. “We wanted a sustainable building that would last 250 years,” said Brian Court, project architect with The Miller Hull Partnership. “That’s just one of the reasons we chose wood.”
Because wood is a sustainable, renewable resource, and because glulam makes efficient use of the materials by bonding smaller pieces of dimension lumber together to form larger beams and columns, glulam was a logical choice over concrete for the Bullitt Center. The podium structure is built with a Type IV heavy timber frame that consists of Douglas-fir glulam beams and columns finished to an industrial appearance grade. According to Brian Oberg of APA-member Calvert Company in Vancouver, Washington, the project required approximately 119,000 board feet of glulam.
Read more in the WoodWorks Bullitt Center Case Study.
Featured Project: Glulam Creates Unique Place of Worship
The framing of Cathedral of Christ the Light, in Oakland, California is unlike any other structure. Two large glulam and steel space frames form the outer walls. The frame consists of two intersecting circles, creating a football-like shape. The inner chords are made with (26) 10-3/4-inch curved glulam ribs, roughly 100 feet in length, varying in depth from 30 inches at the base to 19-1/2 inches at the top. The outer chords are made of straight glulam mullions, which are roughly 103 feet long.
Because the framing is so unique and doesn’t follow any of the structural types listed in the 2001 California Building Code, the City of Oakland Building Department required the engineer of record to establish a peer review committee to help develop the requirements of this framing system. This peer review committee consisted of three university professors and an industry expert. The committee developed the criteria for the structure’s ductility and toughness to resist seismic activity. The building is designed to withstand a 1000-year seismic event. In addition to its magnificent outer beauty, the sanctuary also features two organ lofts built with curved glulam members.
APA EWS member Western Wood Structures, Inc. of Tualatin, Oregon, was the supplier and erector of all the glulam and steel components. The glulam ribs and the frames for the organ loft were manufactured by Alamco Wood Products, Inc. of Albert Lea, Minnesota. All other glulam members were manufactured by APA EWS member American Laminators of Drain, Oregon.
Read more in the Cathedral of Christ the Light Case Study.