Structure Type: built works - dwellings - houses - apartment houses

Designers: CollinsWoerman, Architects (firm); D’Amato Conversano, Incorporated, (DCI) Engineers (firm); PAE Consulting Engineers (firm); Q Tran, Incorporated (firm); Sellen, John H., Construction Company, Incorporated (firm); Sparling Electrical Engineering (firm); Scott Bevan (mechanical engineer); Arlan Collins (architect); John Henry Sellen Sr. (building contractor/civil engineer); Thomas E. Sparling Sr. (electrical engineer); Mark Woerman (architect)

Dates: constructed 2014-2015

6 stories, total floor area: 16,525 sq. ft.

4558 7th Avenue NE
University District, Seattle, WA 98105

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The Bellevue, WA-based developer, Wallace Properties, financed the 24-unit 47 + 7 Apartment building, located near Interstate 5 in Seattle's University District. Seen from the exterior, the building displays notable steel cross-bracing, and was built from many prefabricated components. Wallace hired the firm, Sustainable Living Innovations, a division of Seattle's CollinsWoerman Architects, to use their new construction method. Sellen Construction worked with SLI to erect the building, and DCI Engineers served as the apartment tower's structural engineer.

Building History

The high level of prefabrication utilized to erect this building made it notable, at a time when Seattle was being filled with conventionally constructed "5 over 1" reinforced concrete and wood-frame, six-story mixed-use developments. The website said of 47 + 7 in 2023: "Design and development of a 24-unit studio and one-bedroom apartment building at the northwest corner of 47th and 7th in the University District. This innovative project utilizes our patent-pending approach that optimizes what is built on-site versus what is built off-site." (See, "47 + 7," accessed 03/30/2023.)

A CollinsWoerman subsidiary, Sustainable Living Innovations (SLI), produced this prefab method of building steel frame and concrete towers to create a more efficient construction process and a stronger product. The Seattle Daily Journal of Commerce (DJC) described the process in a 2015 article: "For 47+7, crews constructed the building systems, walls, cabinets and windows off-site, and then loaded them onto concrete floor slabs that were poured on-site. A computerized hydraulic lift pulled each loaded slab up through a prefabricated steel frame. The initial slab was bolted to the top of the frame and the components installed. The process was repeated for each floor below." See Benjamin Minnick, Seattle Daily Journal of Commerce, 35-story tower at 1800 Terry may be built using modular system. 12/14/2015, accessed 09/30/2016.) Wallace Properties wanted to be the first developer to use SLI's kit of parts approach, as it felt that significant cost savings could be achieved with it. A Wallace representative stated in 2013: "...A developer can also achieve economies of scale by using the same type of modular units on other projects rather than building new on each site. The buildings would look different from the outside as the skeleton and skin can be changed. 'Its design potential is really limitless....'" (See Lynn Porter, Seattle Daily Journal of Commerce, "U District project will be the first test of a new way to build," 03/07/2013, accessed 09/30/2016.)

While woodframe construction is limited by Seattle fire codes to seven stories, the SLI method was approved by the city for buildings of up to 12 stories in height.

47 + 7 was completed in the spring of 2015 and is quite visible from US Interstate 5.

Other contractors on the project included Sparling, the electrical engineering firm, who worked with Q Tran, Incorporated, of Milford, CT, on the LED lighting design, and PAE Consulting Engineers, who served as the mechanical engineers.

Building Notes

The building contained small one-bedroom units, some containing 595 square feet, others with 466.

PCAD id: 20657