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World-Record Wood Structures: Mass Timber on The Rise

By Scott Lewis

wood1 — **Tallest Timber Building in the World: Mjøstårnet, Brumunddal, Norway, 85.4 meters.** The 18-story, 11,300 sq m building was designed by Voll Arkitekter, and completed in 2018. It contains a hotel, apartments, offices and a restaurant. Moelven Limtre, the project’s structural engineer, specified and supplied glue-laminated-timber columns, beams and diagonals, and cross-laminated-timber elevator shafts, stairs and floors. Moelven was also responsible for installing the mass timber structure. Hent AS was the turnkey contractor.

The building was erected with a crane lifting four-story engineered wood assemblies, weighing 10 tons each, into position. “This was the first time we used this technique on a large building,” says Rune Abrahamsen, CEO of Moelven. “Previously we had preassembled large trusses and components in our factory to ensure that all parts fit together. From now on we will rely on our machinery and production to a higher degree and install components without prior preassembly.”

]The glulam elements are connected with slotted-in steel plates and dowels. The curtain wall is made of prefabricated timber-frame elements with Rockwool insulation. On the outer side there is a gypsum windstopper and wooden boards. The boards are thermally treated and also pressure treated with a fire retardant liquid. The building is owned by AB Invest, a developer.

*Photo Courtesy Moelven*

wood2 — A vertical truss being lifted into position.

*Photo Courtesy Jens Haugen/Anti/Moelven Limtre AS*

wood3 — There are 2,600 sq m of timber in Mjøstårnet.

*Photo Courtesy Anti Hamar/Moelven Limtre AS*

wood4 — **Largest Mass Timber Building By Floor Area: T3, Minneapolis. 224,000 sq ft.** T3 is a seven-story office building completed in 2016. It was designed for developer Hines by Michael Green Architecture and architect-of-record DLR Group, with structural engineer Magnusson Klemencic Associates.

The building contains spruce-pine-fir nail-laminated timber (NLT) panels in combination with a spruce glulam post-and-beam frame and a concrete topping slab. Columns were connected to columns by epoxy-glued rods, while beams were joined to columns by steel bearing connectors. StructureCraft fabricated the engineered wood components. Hasslacher Norica Timber supplied the glulam to StructureCraft for the columns and beams.

Construction crews erected 180,000-sq-ft of timber framing in nine and a half weeks—a speed of nine days per floor. The building’s structural bays are 20 ft by 25 ft, with the timber beams spanning 25 ft and the NLT panels spanning 20 ft. The curtain wall is weathering steel. Kraus-Anderson Construction Co. was the general contractor.

*Photo Courtesy Ema Peter*

wood5 — The use of large prefabricated floor panels reduced erection time.

Photo Courtesy *Ema* Peter

wood6 — **Largest Wooden Dome: Superior Dome, Marquette, Mich.** Northern Michigan University’s dome stadium, also known as Yooper Dome, hosts football games, track meets and other sports. It is a 272,900-sq-ft geodesic dome, 163 m in diameter and 44 m tall.

The university chose wood because it was less expensive than concrete or steel. TMP Associates, Bloomfield Hills, Mich., designed the dome. R.E. Dailey & Co., Southfield, Mich., a subsidiary of Perini Corp., was the general contractor.

The dome consists of 400 preassembled wooden triangles, which form a three-dimensional grid system of intermeshing circular ribs. They are made up of 15- to 45-ft long glue-laminated beams supplied by Western Wood Structures Inc.

The 580 Douglas fir beams that make up the frame weigh 800 tons. The dome is designed to support 60 lb per sq ft of snow and to withstand up to 80 mph winds.

The dome’s 2-in.-thick Douglas fir deck is covered by 3 in. of insulation and a single-membrane roof of synthetic rubber. A five-sided, 20-ft-high cupola sits on top of the dome. Equipped with a skylight, it also exhausts air.

The arena has 15 canopy entrances with triangulated rooflines projecting outwards. The dome is supported by 40 reinforced-concrete buttresses, enclosed in the arena’s perimeter concrete wall, and anchored in a post-tensioned concrete ring 4 ft below grade.

The facility was completed in 1991 at a cost of $21.8 million. It seats 8,000.

*Photo Courtesy Bobak Ha'Eri/Wikimedia Commons*

wood7 — **World’s Largest Freestanding Wooden Structure: Hangar B, Tillamook, Ore.** Built in 1943 to house U.S. Navy blimps, Hangar B is the largest clear-span wooden structure in the world. It is 1,072 ft long, 296 ft wide and 192 ft tall, with a footprint of 7.28 acres. Its doors are 120 ft tall, with six sections, each weighing 30 tons.

The hangar was designed by Arsham Amerikian, chief engineer of the U.S. Navy’s Bureau of Yards and Docks, and built by Timber Structures Inc. During World War II it housed K-class airships, which carried out antisubmarine patrols and were equipped with radar, sonar buoys, machine guns and bombs. Naval Air Station Tillamook was decommissioned in 1948. Since 1994 it has housed the Tillamook Air Museum, with a collection of American and foreign military aircraft.

*Photo Courtesy Tillamook Air Museum*

wood8 — Because of the demand for steel for war needs, the hangar was built out of wood. The building contains 2.5-million board ft of Douglas fir.

*Photo Courtesy Tillamook Air Museum*

wood9 — The naval blimps were 252 ft long, 90 ft in diameter and filled with helium.

*Photo Courtesy Tillamook Air Museum*

wood10 — **World’s Tallest Conventional Wood Building: Sakyamuni Pagoda of Fogong Temple, China**. Erected in 1056, the Sakyamuni Pagoda is the oldest fully wood temple in China.

Located in a rural area of Shanxi Province, the 67.3-tall temple has a 4-m-tall stone base, nine stories, five sets of eaves and a 10-m steeple. Its pillars and columns are joined to the roof frame with interlocking wooden brackets, known as dougong.

First developed over 2,000 years ago in China, dougong reduce the amount of strain on beams when transferring their weight to a column. Dougong also provide structural elasticity, and have enabled the pagoda to withstand damage from numerous earthquakes over the centuries.

*Photo Courtesy Wikimedia Commons*

wood11 — **Tallest Wooden Tower: Gliwice Radio Tower, Gliwice, Poland, 118 m**. At the time of its erection in 1935, Gleiwitz (now Gliwice) was part of Germany. The tower was constructed of wood because steel structures caused interference with radio signals.

The tower is fashioned with timbers made of larch wood, impregnated with carbolite, a resin, as a preservative. The timber elements are fastened together with bolts of brass, which do not corrode.

The wood members weigh 100 tons, and are supported by four concrete foundation blocks weighing a total of 90 tons. The tower was designed by Carl Lorenz Aktiengesellschaft, and constructed by Christoph & Unmack, Niesky OL. It currently carries multiple transceiver antennas for mobile phone services and a low-power FM transmitter.

The current administrator of the tower is Śląska Sieć Metropolitalna (Silesian Metropolitan Network). The tower has a sobering historical pedigree: on Aug. 31, 1939, Germany staged a fake “Polish” attack on the Gleiwitz radio station as a justification for their invasion of Poland that night—the opening act of World War II.

*Photo Courtesy Wikimedia Commons*

wood12 — The tower's wooden components are held together with 64-cm-long brass bolts.

*Photo Courtesy Wikimedia Commons*

wood13 — **World's Longest Wooden Vehicular Bridge—Powder Point Bridge, Duxbury, Mass., 2,200 ft.** The bridge was originally constructed of southern yellow pine in 1892, at a cost of $30,000. It was 20 ft wide and included a 24-ft wide drawbridge to allow boats to pass. The drawbridge was damaged in the 1930s and removed. Originally, the span served pedestrians, bicyclists and horse-drawn carriages. After sustaining fire damage in 1985, the bridge was rebuilt using tropical hardwoods that would resist marine borers and fire—basralocus wood from Suriname for the piles, and bongossi wood from West Africa for the superstructure. The replacement bridge cost $3 million and opened in 1987.

*Photo Courtesy Laurie Wenham*

wood14 — **Tallest Existing Wooden Trestle: Goat Canyon Trestle, Calif., 186 ft.** The trestle was constructed in 1933 as part of the San Diego and Arizona Eastern Railway. The canyon is an offshoot of Carrizo Gorge, within the Jacumba Mountains in Anza-Borrego Desert State Park. The trestle was designed by the railroad’s chief engineer, Carl Eichenlaub.

Redwood timber was used, rather than steel, because of the extreme temperature fluctuations in the gorge—up to 75°F in a day. To resist the canyon’s high winds, the trestle was built with a 14° curve. Sections of the trestle were assembled at the bottom of the canyon and lifted into place.

The section of railway that includes the trestle closed indefinitely for repairs in 2008. A Mexican freight railroad, Baja California Railroad, is currently assessing the line before deciding whether to repair it and resume operating. Meanwhile, the trestle remains a popular destination for hikers. It is currently owned by the San Diego Metropolitan Transit System, with Baja holding a lease.

*Photo Courtesy Wikimedia Commons*

wood15 — **Longest Existing Wooden Trestle: Rochfort Trestle, Mayerthorpe, Alberta, Canada, 2,414 ft.** The Canadian Northern Railway erected the trestle in 1914, 78 miles northwest of Edmonton. Piles were driven by horsepower, with horses traveling in a circle to raise the weight on the pile driver.

The construction cost was $11,000. In 1934 the portion of the trestle spanning the Little Paddle River was replaced with a steel superstructure, and a large section had to be rebuilt in 1956, following a fire.

In 2005 a 30-m-long section was removed to create a highway underpass and replaced with a steel girder section. Since 1917, the trestle has been owned and operated by CN, also known as Canadian National Railway Co.

*Photo Courtesy Jason Woodhead/Wikimedia Commons*

While still trailing far behind concrete and steel as the structural material of choice, mass timber frames in the U.S. are on an upswing, in great part because the sustainable material is renewable. There are 445 engineered wood projects completed or under construction, and 534 in design, according to WoodWorks, a nonprofit technical support group promoting the use of wood in nonresidential and multifamily buildings. And the number of new mass-timber buildings in North America will double every two years, predicts the Forest Business Network.

“North America is in the early stages of a mass-timber construction boom, driven by increasing demand and expanded building code acceptance of larger mass-timber structures,” says Robert Malczyk, director of mass timber engineering at Katerra, a supplier and fabricator of cross-laminated timber (CLT). “We’ve seen adoption of mass timber across a range of building types, market sectors and [locations] particularly in academic, institutional and multifamily sectors.”

The U.K. market is more mature. There are some 550 completed mass timber buildings, estimates architect Andrew Waugh. His data is based on a study he conducted in 2018, as well as on subsequent conversations with major suppliers of engineered wood products, such as glue-laminated timber (GLT) and cross-laminated timber. Waugh designed the first mass timber building in the U.K., which was completed in 2003.

Late to the Game

“The U.S. was late to the game, but now momentum has hit our shores,” says Ben Kaiser, founding partner of Kaiser + Path, an owner-architect-general contractor in Portland, Ore., that has been producing mass timber buildings in the area for over 20 years.

Mass timber generally refers to buildings whose primary load-bearing structure is made of solid or engineered wood. The oldest solid-wood product, glue-laminated timber, consists of a number of layers of dimensioned timber bonded with structural adhesive, and is used mostly for columns, beams and trusses. Structural composite lumber, made by layering veneers, strands or flakes with adhesive, is used for rafters, headers, beams, joists, studs, columns and I-joist flanges.

Cross-laminated timber is made from solid-sawn lumber, with adjacent layers cross-oriented and bonded with structural adhesive. It typically is used for load-bearing walls and floor diaphragms with spans of up to 20 ft.

Tall wood buildings have faced regulatory restrictions, as well as a general reluctance to innovate. But change is on the way. The 2021 International Building Code, issued in November,, allows tall wood buildings of certain occupancy types to reach up to 18 stories. Washington, Oregon, Utah and the city of Denver have already adopted the new tall wood provisions, and they will become effective in California next July.

U.S. Suppliers Increase in Number

In the U.S., in response to greater demand for mass timber, there has been an increase in the number of suppliers, especially of CLT. The first two U.S. CLT plants opened in 2012. Currently, there are eight operating and three more in development. Three of these have earned chain-of-custody certifications from the Forest Stewardship Council-U.S.

The estimated annual manufacturing capacity of the 14 mass-timber panel plants operating across the U.S. and Canada at a practical, versus a maximum, capacity is 910,000 cu m, as of late 2019, according to WoodWorks.

Even tall mass timber is no longer as much of an oddity. Arup is the structural engineer for the Haut building, a 73-meter-tall residential tower in Amsterdam. Construction reached the sixth of 21 floors in August. Completion is expected next summer.

Takenaka Corp. is currently building Proud Kanda Surugadai, a 14-story, hybrid concrete and wood-framed condominium in Tokyo. Floors two to 11 will incorporate laminated veneer lumber and reinforced concrete walls, while floors 12 to 14 will use cross-laminated timber. It is expected to be completed next March.

Tallest Mass Timber Building

The tallest mass timber building in the world at present is Mjøstårnet, an 85.4-m tall, mixed-use building in Norway (see longer entry in accompanying slide show). It is expected to be surpassed by Ascent, a 19-story hybrid timber-and-concrete building under construction in Milwaukee. The joint venture general contractor of Catalyst Construction and C.D. Smith expects to start timber framing next May and complete it by the summer of 2022.

Last month the developer First Community Housing selected Lendlease to build the 305,000-sq-ft McEvoy Apartments in San Jose, Calif.—a hybrid structure. Plans for the affordable housing complex call for two, 12-story towers over a concrete podium. As designed, the towers will consist of a mass timber frame with a traditional lateral-load resisting system of either steel or concrete.

“It was determined that mass timber would be the optimal building technology, given its environmentally sustainable benefits of carbon sequestration, biophilic impacts on residents, speed in construction and adaptability of design,” says Russell White, general manager for design build at Lendlease Americas.

Panzica Construction Co. is constructing the mixed-use Intro building in Cleveland. The 515,000-sq-ft building has a hybrid structure, with levels two to nine in timber and the lower levels, the core and the stairwells in concrete. “Mass timber for us really started as [a market] differentiator and then snowballed to become a national case study project for sustainable vertical, transit-oriented urban development,” says Dan Whalen, vice president of Harbor Bay Real Estate Advisors, Intro’s developer. Completion is expected in early 2022.

“Just in the last two years owners have come to us and asked for timber,” reports Waugh. “Before that we had to convince them. With the commercial market we are seeing a real difference. The market is led by investment – money wants to be green.”

Scott Lewis was Associate Editor of ENR.

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