Highlights from this Month's e-Newsletter
One North Office Buildings
Can you design a building to reflect community values? How do you translate a mission focused on energy efficiency and waste reduction into a physical structure? How can you connect building tenants with their neighbors? One North, a three-building office development in Portland, Oregon, found answers to these three questions—with innovation, vision and ingenuity. And engineered wood stands tall in the center of it all.
One North is comprised of three multi-story timber-framed office buildings called The Radiator, One North: East Building and One North: West Building. The three structures surround a large 14,000-square-foot courtyard, open to the street for use by both tenants and neighbors. One North differentiates itself in a number of ways, said Ben Kaiser, project architect and developer from the Kaiser Group. “We started with the goal to have three buildings that shared resources for the benefit of the block. The courtyard was designed to be a community space, given back to the neighborhood."
In addition, the developers wanted the buildings to have a strong sustainability focus. The team chose glulam to frame the structures to take advantage of the beams’ carbon-sequestration capabilities. The glulam framing, which was left exposed to the interior, also met the aesthetic goals of the finished space. Wood’s natural insulating qualities help keep energy use extremely low—much lower than the standard for similar commercial buildings. The exteriors of the One North: East and One North: West Building structures were padded with three inches of insulation to optimize energy performance; The Radiator utilizes two layers of DensGlass® outside and batt insulation on the interior cavity. All three structures use solar panels and LED lighting throughout. Operable windows allow natural ventilation during warm months, and fins on the west face of one building even track with the sun during the day to provide shade. The development was designed to help attract environmentally-minded, creative firms who appreciate the open floor plans and high ceilings in each structure.
Radiator Building—Portland’s first five-story wood office building in a century
The Radiator (named because the designer wanted the structure to radiate out into the community and invite people in) is a 36,000-square-foot, five-story timber-framed structure. The Radiator is touted as the first five-story office building in Portland to be framed with timber during the last 100 years. The L-shaped structure features exposed Douglas-fir glulam beams and columns, as well as T&G cedar decking.
“The Radiator kicked off a heavy timber building boom in the city, proving the financial viability of building larger buildings in wood, and reminding the design and build industries to recall this tried-and-true construction type,” said Kaiser. “The main priorities of the project were the resuscitation of the Oregon timber industry, a critical part of the state’s economy and heritage, as well as to illuminate the environmental benefit of the carbon sequestration that is inherent in timber construction. In direct contrast to steel and concrete, building with timber actually reduces the carbon footprint of a building’s construction process.”
WoodWorks provided technical support to the designers, and The Radiator recently won the organization’s 2016 Multi-Story Wood Design award.
One North: East and One North: West Buildings— purpose-built for energy efficiency
The two adjacent structures, named One North: East Building and One North: West Building, were also designed to push the accepted standards for energy efficiency in commercial construction in Portland. Cory Hawbecker from Holst Architecture said both buildings are modeled to perform 50 percent more efficiently than an average office building. “Our sustainability strategies included exterior shading, a super-insulated, airtight building envelope, use of wood for the structure and use of sustainably-harvested cedar wood siding, which was locally sourced.”
Hawbecker said much of the vision for the One North: East and One North: West Buildings came from the developer, Eric Lemelson of Karuna Properties II, LLC. “Eric is interested in climate change and in helping people and society adapt. So, we wanted to create a model for an energy-efficient project that could also be built responsibly. Eric was particularly interested in the wood structure and the wood cladding; he didn’t want to see us use steel or concrete because wood is a much better construction material from a sustainability standpoint. He also wanted this to serve as a replicable financing model.” Wood’s affordability advances that goal.
Read more about the project in APA Case Study: One North Office Buildings, Form S120.
Mind the Gap
Temporary Expansion Joints in Large Structures
The building was large, but not unusual, with an equally sizeable floor sheathed with OSB. What was unusual was the enormous amount of rain that unexpectedly doused the site during construction. Luckily, the developers had the foresight to include temporary expansion joints, and the project continued without a hitch after the deluge dried up.
While temporary expansion joints may seem like a minor detail, omitting them can have severe consequences where humidity or moisture come into play. When wood structural panels (plywood and OSB) are exposed to moisture during construction, the wood absorbs moisture, and panel expansion may occur.
“We recently saw an example of just how important expansion joint detailing is,” said Karyn Beebe, PE, an engineered wood specialist for APA. “In a large condominium project, a 174-foot long floor was exposed to nine inches of rain within two months during the framing stage of construction. The floor panels expanded and the framer reported the first story walls were leaning out of plumb up to 1-1/2 inches, forcing the crew to realign the walls.”
The accumulated panel expansion and resulting misalignment occurred in the first phase of a two-phase development. The design team was able to learn from the incident and incorporate temporary expansion joints in the plans for the second phase of the project.
For smaller buildings, the recommended 1/8-inch spacing of floor, wall or roof sheathing panels will usually allow panels to expand without affecting wall alignment, assuming no unusual moisture conditions or aggressive fastening schedules. The larger the building, the larger the potential for adverse effects to framing caused by expansion of moisture-laden panels, Beebe explained. In large buildings with continuous floor or roof decks constructed of plywood or OSB, the effects can be more noticeable. Results of the expansion can include the displacement of framing at the building’s perimeter and out-of-square window and door openings.
Builders can eliminate displacement from the equation during construction by using temporary expansion joints for buildings that have a length or width exceeding 80 feet. This should be done in addition to providing 1/8-inch spacing at all panel ends and edges.
Temporary Expansion Joints for Large Floors
These joints consist of an extra-wide spacing gap, such as 3/4 inch for floors, between panel ends at the desired expansion intervals. Panel ends can be supported on adjacent doubled floor joists, but not fastened to them until later, allowing for expansion. (Temporarily placed panels should be held in place with enough fasteners to prevent unsafe jobsite conditions, such as fall or trip hazards.) It is also important to ensure that wall bottom plates do not extend across the expansion joint. After the building is closed in, fastening of the floor panels can be completed. If necessary, a filler piece or non-shrink grout can be installed to fill the gap between panels. For shear walls or braced wall panels, a short lumber bottom plate filter block and doubler can be added between studs to splice the bottom plate of walls over the expansion joint.
Temporary Expansion Joints for Large Roof Decks
While constructing large roof decks, sheath 80-foot sections at a time, omitting a roof panel between sections. This provides effective temporary expansion joints. The installation can be completed with “fill-in” panels cut to size as necessary. Cover the roof deck with roofing underlayment as soon as practicable for protection against excessive moisture prior to roofing application. This process can be scheduled in sections to avoid exposing an entire expanse of roof deck to weathering during construction.
Curtail Callbacks and Corrections
While designers or contractors may opt out of including temporary expansion joints in large buildings—for example, in warm, dry regions or in summer months—this omission should be undertaken in the full understanding that the designer or contractor may face the potential risk of structural modifications or repairs if moisture-related expansion causes problems. Incorporating temporary expansion joints in large buildings is good construction practice, and APA recommends this for all buildings 80 feet or greater in length or width.
For more detailed information on temporary expansion joints, including temporary drainage holes, consult APA Technical Note: Temporary Expansion Joints for Large Buildings, Form U425.
Coming in 2017
- Floyd Cultural Center: Many stakeholders played a part in directing the vision for the new Floyd Cultural Center at Washington State University. A free-flowing space that honors the Nez Perce tribe, the center used custom glulam to achieve a "unique signature form and image with non-western approach." Look for our Designers Circle ad, featuring the Floyd Center, in the Winter edition of Wood Design & Building magazine.
- New Year, New eNewsletter Platform: We’re updating the look and feel of our eNewsletters in 2017. The informational content won’t change, but you can expect a refreshed, accessible layout and improved deliverability.
Outside the Circle