Architectural glulams: Beauty and brawn

Most builders are familiar with glue-laminated lumber, or glulams, as headers, ridge and floor beams, and for other long-span framing applications, as well as for post-frame and other columns. In such framing applications, glulams compete with dimensional lumber, steel beams, and engineered products such as LVL (laminated veneer lumber) and parallel-strand lumber (PSL). Deciding which to use depends on the situation and pricing, but preference often plays the biggest role. LVLs and PSLs are stronger than glulams of the same size, but the latter are often more cost-effective.
But in many architectural applications, glulams are the clear winner. In exposed trusses and post and beam frames, glulams can mimic solid-sawn lumber, with greater dimensional stability and lower cost. (PSLs are gaining acceptance in timber-frame construction, but only for those who want the distinctive, striped appearance of the parallel strands.) Glulams can also be curved or shaped during the manufacturing process, allowing some spectacular designs in buildings that accentuate their roof vaults. Depending on whether the style calls for visible laminations or not, glulams can be stained to mimic the look of solid-sawn timber or varnished to accentuate the grain and glue lines.
Glulams for architectural applications can be either stock or custom. Stock glulams are available in 1-1/2 in. increments and come either flat or with slight cambers. They are manufactured in lengths up to 80 ft. and shipped to distributors, who cut them to customers’ dimensions. Custom glulams are made individually, and can be assembled with an astonishing variety of shapes and curves.
There are four main grades of glulams. Industrial grade has allowances for knots, glue smears, and low laminations that make them unsuitable for architectural applications. Framing grade has similar visual criteria, but are sized to match dimensional lumber widths. Architectural grade glulams, in addition to fewer knots and color-matched filler, are planed and sanded down, resulting in widths of about a half inch less than standard framing sizes: 3-1/8, 5-1/8, 6-3/4, etc. There are also premium appearance grades and special rustic surfaces available.
Because knots are limited to a single ply, manufacturers can assign glulams precise design values, including bending stress (Fb), horizontal shear (Fv), and modulus of elasticity (E). The strength depends on the species and the physical lay-up of the laminations. Stronger boards are generally used for top and bottom laminations; some are made with machine stress-rated lumber in specified laminations for particular structural needs or fire ratings.
While Douglas fir and Southern pine predominate, glulams are made from hem fir, cedars, hardwoods, and other species. Glulams using preservative-treated wood have rot resistance superior to solid timbers, since the chemical penetrates more deeply into the plies. However, adhesives are still being developed for wood treated with some substitutes for chromated copper arsenate (CCA), such as alkaline copper quaternary (ACQ).
You don’t have to look far to find glulams keynoting architectural designs. Churches are particularly popular sites for curved and shaped glulams supporting vaulted ceilings, and the warmth of the material serves to bring the natural world into worship. Recreational facilities and many open commercial spaces also see a lot of glulams.
For custom, high-end applications, the specification, assembly, and erection is often delegated to a specialized glulam contractor. Wood-Lam, based in Pewaukee, Wis., handles much of the custom glulam work in southeastern Wisconsin. The company designs and assembles glulam trusses and framing systems, but the glulams themselves it buys — stock beams from Filler King in Homedale, Idaho, and custom beams from Alamco Wood Products in Albert Lea, Minn. The company owns a 40-ton crane and a boom truck to erect bigger frames.
For a complex design, says Wood-Lam’s Tom Osenga, it can take about six weeks to make shop drawings, and about as long to assemble the trusses. On some projects, glulam frames can be shipped fully assembled and quickly erected on site; others are put together in the field.
Nearly all of Wood-Lam’s work is architectural — about 60 percent churches, some commercial, a few indoor water parks, and a handful of custom residences. One atypical project was a car storage barn — if you can call Karl Otzen’s elegant building a barn. Otzen wanted a building to house his collection of classic automobiles and wooden boats on the grounds of the former Wrigley Estate, known as Green Gables, at Lake Geneva, Wis. Sensitive to local history, he set out to design a structure similar to an old gambrel-roofed barn that used to stand on the estate.
Otzen and his architect, Thomas Stelling of Burlington, Wis., inspected several other timber-framed buildings in the area and noted the warm aesthetic qualities of exposed wood framing and roof decking. They decided on a timber design for the new barn to evoke the traditional aesthetic of this century-old community.
But solid-sawn timber presented some problems. “The client originally considered solid-sawn timber framing, but determined that the glued-laminated members have more precise tolerances,” says Osenga. “The beams have greater stability to resist twisting and warping, often caused by higher moisture content in solid-sawn timbers.”
Glulams, he notes, are laminated from smaller boards already kiln-dried to a low (generally less than 15 percent) moisture content. Solid-sawn timbers are expensive and difficult to dry because of the extended kiln time necessary. Their dimensional stability also allows glulams to be fitted and assembled off-site.
Stelling found Wood-Lam, and got a tour of the company’s various projects in the region. There were plenty to choose from. “We’ve done so much work around here,” says Osenga. “A timber-frame restaurant called Winchesters, a timber-framed office building, the carpenters’ union building, which has an entryway of Alaskan cedar glulams, and a couple churches with curved glulam arches. We can give quite a tour.”
The “barn” designed by Stelling has the traditional gambrel roof with exposed, oversized timber trusses and wood decking. The building is 28 ft. by 128 ft., with two 28 by 20 ft. wings projecting from the center. Glulam trusses span 28 ft., with 8-3/4-in. by 9-in. top chords and 8-3/4-in. by 21-in. bottom chords to support second floor loads. The web trusses are all 8-3/4 by 9-in.
Wood-Lam fabricated the trusses out of rough-sawn glulam stock and some dimensional lumber, then disassembled and shipped them to the jobsite for erection. Wood-Lam installed the 2×6 roof decking as well. Curved glulams were mounted on the roof deck to give the eave a gentle curve.
Although concealed connections were possible, Otzen, an engineer and inventor, preferred thick black hardware. Osenga concurred with the choice. “It’s more labor to install concealed connections, and you can’t see if anything is going wrong.”
The resulting structure fits into Green Gables nicely. “The warm aesthetics of the laminated timber framing give the building a strong presence that is compatible with its surroundings,” says Stelling. Dormers in the new barn also harmonize with the gables in many of the older buildings nearby.
But the design is still entirely modern. The structure has three levels with a full basement for boat and car repairs, a main floor display area, and an upper loft. The laminated framework is erected over a pre-stressed Spancrete floor. Stelling’s design also gives special attention to fire safety and proper HVAC climate control.
While glulams are well suited to traditional heavy timber framing, they are also suitable for clear-spanning areas with minimal weight and expense. One such application is in recreational facilities, ranging from football fields to backyard swimming pools. Wood-Lam has built long-span glulam roofs approaching 100 ft. for several indoor water parks in Wisconsin. Glulam’s ability to absorb and give off moisture, the resistance of treated wood to rot, and concerns about rust on steel alternatives make glulams the preferred material for many such enclosures.
Some 7 million U.S. homes have swimming pools, and those not in year-round moderate climates are all candidates for enclosures. In Upstate New York, homeowner Tom Bartodziej had a 28 by 66-ft. glulam-supported covering erected over his 16 by 32-ft. pool, with extra space for a bathroom, bar, and lounge area. The 6-in. wide curved glulams were designed and fabricated by Unadilla Laminated Products of Unadilla, N.Y.
The glulams were delivered in two pieces to the pool site, where they were bolted together at the peak and set in to place with a crane by John Cole of JRC Construction, a remodeling contractor.
“The timber arches provide a good combination of strength and aesthetic warmth,” says Cole. The space is heated by a half-million Btu wood-burning boiler, which also supplies hot water for radiant heat in the floor.
Ice rinks are also good candidates for glulam enclosures. At the high end, renowned architect Frank Gehry opted for wildly swooping glulams to cover the Disney ICE arena in Anaheim, Calif., several years ago. The curving glulams look like a deliberate architectural choice, but they actually won out over steel based on cost.
A bit closer to home, businessman Jim Maxwell had the large ice skating rink at his New Mexico home enclosed with 52-ft. clear-span glulam trusses. The trusses, made from 33-in. and 12-in. glulams 6-3/4-in. wide, were assembled by Timberweld, Inc., based in Billings, Mont., and erected by contractor Jim Pitcher.
Treated wood is often used for glulams in high-moisture situations, and CCA will remain permissible for glulams, but homeowner fears may create some problems. Alternative treatments such as ACQ are available, but new laminating adhesives need to be found and metal corrosion concerns addressed. In the short run, Wood-Lam has turned to glulams made from naturally rot-resistant Alaskan Yellow or Port Orford cedar for high-moisture applications; they’re more expensive, but don’t come with any restrictions.
Glulams were developed in the 1930s and have been in common use for decades. Osenga says that while his sales keep rising, glulam’s market share has suffered since the 1970s. “The steel guys have been doing a great job marketing metal construction, going to schools and architects, educating builders. Even LVLs are selling better than glulams, and glulams are cheaper. We just haven’t marketed them as well.”
New technologies may help boost glulams into new arenas. Fiber-reinforced glulams offer even higher design values. And glues that closely match wood tones promise new aesthetic avenues.
In either case, glulams seem guaranteed a secure future in architectural applications. No other product so adeptly combines the strength of material engineering with the natural warmth and appeal of wood.

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