When Oregon-based contractor R&H Construction got the commission to build a pair of office buildings on an urban lot in Portland, the assignment came with some heavy demands in terms of sustainability, environmentally responsible sourcing of materials, and community involvement.

Owner group Karuna Properties II is headed by Eric Lemelson, a noted advocate for sustainability in a city at the forefront of the green building movement. His vision for the One North development called for a multi-use, commercial development incorporating innovative design attributes, high standards of energy efficiency and the use of environmentally sustainable and ethically sourced materials.  

One North comprises three office and retail buildings, the Radiator and East & West Buildings surrounding a 14,000-square-foot landscaped public courtyard. R&H Construction was the contractor for the East building (42,938 gross square feet over four stories) and the West building (42,610 GSF over five stories). 

Sustainability in Design

The most visible distinction of the East and West buildings are the curves and apertures which are designed not just to look great, but to optimize the use of sunlight and shade for lighting and temperature control inside the buildings so that they perform 50 percent more efficiently than required by code. A highly insulated and airtight shell, efficient mechanical systems and limited thermal bridging inside maximize the energy-saving potential. Additionally, the buildings are timber-framed, using glulams and engineered wood decking as the primary structure, with bolted steel connections. According to the owner, these are the first new timber-framed office buildings built in Oregon in over 100 years. The advantages are sustainability, along with the ability to support open floor plans, high ceilings and large windows.

"The unique design elements presented challenges to the entire construction team," said Adam Petersen, Project Manager for R&H Construction.

Post-tension concrete was used in construction on the second floor of the East and West buildings in order to facilitate the wood construction above. Petersen said the concrete work was not particularly challenging except for the curves, one factor that led the company to acquire the Autodesk Revit software to create 3-D models of the design. Although they still printed out paper plans, with marked elevations and so forth, the computer model directed a lot of work on the ground. R&H used a beta version of Point Layout, an AutoDesk bridging software to connect the 3-D model directly to their survey equipment. On this project they used a Topcon DS-203 Robotic Total Station with Tesla Data Collector.

"Using the Total Stations along with Point Layout was like doing the work on an iPad," said Petersen. "Rather than using string and pencil to mark a radius, or masonite cutouts for the PT decks, we just input points every 6 inches on the computer model and the data directed the machine." Having the system point the laser saved enormous amounts of time and effort in measuring and cutting structural timber as well. Petersen said supervisors, foremen and carpenters who worked with the system are sold on its benefits. "Now they won't do any job without it," he said.

Choosing Efficient Materials

One change during the course of the project was the steel framing for the apertures. Originally, these were going to be red iron in cages, covered with a lighter gauze framing. Based on a prior experience, R&H suggested the use of cold-formed steel frames for the apertures instead. The change increased the project's use of LEED-certified materials, and meant the frames were almost 60 percent lighter in weight, could be installed more quickly. The curved, cold-formed steel framing was pre-fabricated by Radius Track Corporation in Minneapolis.

Weekly cross country meetings took place with the partners gathering in front of 60-inch screens in their respective conference rooms and "flying around in the model" together as they discussed issues that came up.

Meeting the desire to use only second-growth western red cedar for the siding, sparing old growth, was another challenge. The owner also wanted the ability to track the exact source of the material used. "We went to our normal suppliers with that request and sort of got nowhere," said Petersen.

Finally, they got a referral to the Northwest Natural Resource Group, a coop of private owners in Mossy Rock, Washington. The design and construction team visited the property, met the foresters, and those who would be harvesting the wood. "It was not the usual scenario where you dial up the lumber supplier and get your order dispatched immediately," said Petersen. In this case it took up to six months for delivery. "Sometimes we would get a call, sorry, there was a heavy snowfall this week and we couldn't bring in another tree."  

The small batch lumber added to the character of the project, you can almost see the individual trees in the successive panels. Though not much more expensive than conventional sourcing of lumber, Petersen said, the process did take its toll on project timelines, and in the end supplemental sources had to be located, while still meeting most of the criteria desired by the owner.

Innovative Project Solutions

Creative solutions were also found to deal with other issues. East building core and shell construction were completed between June 2014 to June 2015. For the West building, which was started later, in November, 2014 (and completed November 2015), the team faced additional challenges in bringing in materials. Confined on one side by the East building, on others by busy roads, on a lot that had almost no lay down area, the team faced the prospect of having to carefully stage deliveries, with full-time flaggers on duty, and tie up traffic every time a delivery came in. Petersen credits the site superintendent with a unique solution.

The team dug footings deeper than called for and held off on pouring the foundation slab on the West building in order to create clearance for delivery. Laying down some additional heavy rock to avoid having the substrate wash away, they created a roadway under the West building which was used as a shortcut to the staging area. 

Attention to everyday details also helped. The contractor reduced traffic in and out of the site by hard plumbing toilets early, so that they wouldn't have to contend with emptying temporary units.

Another innovative aspect was the use of self-erecting cranes in place of a traditional tower crane. "We didn't have to move heavy loads," said Petersen, "But we did have to reach a long way." The best solution turned out to be a Potain HDT80 Self-Erecting Tower Crane. Operators were sent to The Crane School to learn how to run the equipment.

In the end, successfully meeting all the challenges involved in One North made for a memorable and rewarding experience. "Everyone was excited about doing new and different things, hard things, and solving the problems that arose," said Petersen. "In 11 years in the business, I have not experiences this level of teamwork."