Seattle Convention Center’s Summit Building

The Summit building at the Seattle Convention Center, the largest single building ever worked on by MacDonald-Miller, is now open. With a contract value over $100 million, and several years of preconstruction work, MacMiller began onsite work at the convention center addition in September 2019, setting the first four of 35 air handling units. After more than three years of construction, the building opened to the public on January 25, 2023.

“Our fabrication, logistics, and field teams performed phenomenally for this project. Ensuring the fabrication was accurate and that it arrived on site when the crews needed it was an enormous undertaking. Our team made over 2,800 deliveries to the site with fabrication, equipment, and other materials.” – Rylan MacCay, Operations Manager


MacDonald-Miller was selected for this complex project based on project team experience and prefabrication expertise. That experience allowed us to take an integrated approach to the project’s design and building information modeling. When considering early preconstruction efforts, MacMiller worked on the project since 2016, when the scope included providing and installing all the HVAC systems, including mechanical piping, sheet metal, and controls. The size and scope of these systems is incredible, with many duct sections bigger than a full-size train car. The project includes more than 1.6 million pounds of ductwork, with many long runs to accommodate the exhibition halls and gathering spaces. Some of the ductwork is more than 20 feet wide. The most unique aspect of this project included prefabricating a 4,000-ton central plant, creating complex life safety systems, and using a unique construction method due to the large building footprint, which required the steel structure to be installed in phases and presented several sequencing challenges.


Due to the sheer size, the project was a challenge from the start.

“With 1.5 million square feet of single rooms spanning multiple city blocks, the construction sequence and logistics of this project are like nothing else in the country. Adding the hurdles of the pandemic hitting during our peak crew size, a concrete strike, and challenging labor and procurement markets, the level of difficulty only increased. These challenges were met head-on by the project team, and we executed them with distinction.” – Ryan Hunter, project manager at MacMiller.


Most construction projects start on the ground and move up, so one of the biggest challenges of this site was that it was built in a billboard sequence. This unique plan organized the construction into five towers or “billboards” lined up in a row, to brace one another and support the load. Area one went up first, then area two, and so forth, until all 14 levels were completed.

Another aspect unique to the project was that the scaffolding was not as permanent as it may have been on other sites. It sat in place for a day or two to load materials and then moved to a
different location for walls to proceed.

During preconstruction, detailers from MacMiller co-located at the Arup Engineering office to model the systems in 3D to speed up the design and coordination process.

Collaboration was vital with engineers, detailers, and project managers all together in a room to resolve constructability issues early, which allowed MacMiller to prevent problems that would have been very costly to fix later.


Most importantly, this work consisting of more than 797,000 hours, was executed safely, with a Recordable Incident Rate of 0.5. To put this into perspective, the national average Recordable Incident Rate in the construction industry is 3.9

“We did a fantastic job out here on safety. It is unheard of. It would be like if four people worked a full 40-year career and only one of them had a recordable incident.” – Ryan Hunter

MacMiller would not have been as successful on this project without the immense preplanning and collaboration of all team members who were focused and committed to delivering this new space for both the local community in Seattle, as well as the many visitors who will enjoy what the Summit has to offer for years to come.

MacDonald-Miller employees at sitewalk of the Seattle Convention Center

Check out our feature in the Seattle DJC!

Categories: General

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