111 East Grand Office
Engineer-Build
The First Dowel-laminated Timber Office Building in North America
The first speculative office structure in Des Moines in over 10 years, 111 East Grand Office has a prominent location next to city hall. As the design-builders for the timber superstructure, we worked alongside Neumann Monson Architects and Ryan Co. to create the 4-storey mass timber building. With retail at the first level and 3 levels of commercial office space above, this space offers visual, tactile, olfactive, and biophilic connections to its inhabitants. The structural gravity system consists of DLT (dowel-laminated timber – see our Materials Page) panels over Glulam post and beam substructure, and the lateral system is comprised of pre-cast concrete walls and core. This created a fully prefabricated superstructure that could be installed much faster than conventional construction.
StructureCraft won the project after submitting a response to a request for Design-Build proposals in Fall 2017, joining the team of Ryan Co. and Neumann Monson. We were chosen for our extensive engineering and construction experience in large North American mass timber jobs, as well as for our turnkey delivery method which offered sole-source responsibility. Our structural engineering role took the timber superstructure from schematic design to detailed fabrication design, sealing the drawings with our in-house licensed P.E.
Key issues unique to this building included navigating the code approval process, engineering the floors for suitable vibration criteria and MEP routing, understanding the timber supply chain and lead time, planning for on-site weather protection of the timber, and ensuring on-time delivery through efficient site logistics.
111 East Grand’s successful use of exposed timber has allowed it to be an illustrative building to other owners, architects and designers around North America. Numerous design and construction groups have visited the building since completion, inspiring them to investigate the use of this “old” material in modern construction. The overall economy of the project, as well as its on-schedule delivery, further demonstrates that mass timber is truly a viable construction system that is here to stay.
Design
Working with Neumann Monson, we identified innovative ways to reduce the up-front cost premium, while recognizing the back-end advantages of mass timber, including accelerated construction schedule and increased leasing rates. A freestanding precast design was implemented for the rear wall, numerous window sections were eliminated, and various building envelope options were considered. Since the architect wanted to integrate the electrical conduits within the timber structure, the MEP design-build partner had to strategize a way to incorporate routing locations for the exposed conduit and ductwork, while simultaneously giving pleasing aesthetics. StructureCraft provided 4” gaps between the DLT panels, allowing for sprinkler and lighting conduit lines to pass over the beams. We also worked closely with the architect to develop details which “socket” the beams into the columns, creating an aesthetic which celebrates the wood. It also reduces the amount of exposed metal and intumescent paint required of the 1-hour fire rating between the first and second levels.
Throughout design, Neumann Monson, StructureCraft and Ryan Co. developed and shared 3D Building Information Models (BIM), facilitating efficient and precise shop drawings for every component of the project. These models were coordinated with the other consultants’ models (foundations, MEP, and fire suppression). Conflicts between the various systems were resolved through clash detection reports and Virtual Design and Construction (VDC) meetings. Since the MEP and HVAC systems are visible in the completed building, it was crucial to gain a complete knowledge of all routing and harmonization.
Numerous challenges were met on Iowa’s first mass timber structure, such as the skin, roof slope, acoustical considerations, and routing of the MEP/HVAC systems. The team was also in the unusual position of providing guidance to the City throughout the approval process.
Fabrication
The mass-timber DLT panels were manufactured in-house at StructureCraft’s plant. Spruce DLT panels and glulam columns and beams were fabricated with connections fully pre-assembled, allowing the mass timber members to be installed as finished materials. Similarly, the structural connections needed to be architectural. This required a detailed, forward-thinking approach, collaboration, and coordination on the part of the design and construction team. Since the structural connections, fire suppression and HVAC systems are normally not exposed, extra care was taken by the subcontractors during the installation.
Installation
During construction, not only was craftsmanship a top priority, but the team took extra care to protect the structure from the elements and any other potential damage. Temporary protection was planned to shield the structure from the elements, columns were wrapped during concrete pours and interior finish work, and hours were spent re-sanding and sealing to ensure the highest quality end product. Construction began in late June 2018, with Ryan Companies erecting a series of pre-cast panels that create the service core and provide the primary lateral support for the building.
StructureCraft provided erection drawings to choreograph a fast-paced installation. The subsequent arrival in early August of the spruce glulam columns and beams from Austria and the SPF 2x8 DLT floor panels and 2x6 roof panels fabricated in-house by StructureCraft enabled us to be the only trade on site during its erection. Each column, beam, and panel were assigned a number and chronologically shipped to the site to be put into place. Akin to a basswood model in architecture school, the 13 structural bays were erected east to west in approximately six weeks, with a crew of eight including two supervisors and six local carpenters.