Mass Timber Assembly

Neumann Monson Architects

Recognitions: AIA Iowa 2021 Craft Award

Project Description

The 65,000-sf building anchors a high-visibility 265’ x 65’ site two blocks from the river and is the first multi-story office building in North America to employ Dowel Laminated Timber (DLT). After considering Cross Laminated Timber (CLT) and Nail Laminated Timber (NLT) suppliers, the team decided to pursue DLT because the application greatly reduces the need for glue and drastically decreases off-gassing. In DLT, the manufacturer hydraulically inserts hardwood dowels into softwood dimensional lumber. The hardwood expands upon reaching moisture equilibrium and creates a mechanical, friction bond with the softwood. The engineer-fabricator was integral early in the design process and worked with the team achieve greater innovation: a hybridized DLT-precast concrete system. At the south, a precast concrete core houses service and mechanical systems. The core addresses fire code compliance and provides lateral stability for the entire building. This approach resulted in competitive building costs with multiple efficiencies, such as quick erection time, a smaller site crew, and minimized neighborhood disturbance. The structure was erected in phases as three separate ‘towers’ moving from east to west. This enabled the crane to occupy the footprint of the building and transfer west into the staging area. The structure was complete in just in seven weeks, significantly faster than traditional steel frame or concrete building types. DLT’s refined aesthetics enable the structure to remain exposed as an interior finish and eliminate the need to add dropped ceilings or column wraps. Ground level retail spaces and three floors of office space above offer biophilic materials, carbon sequestration, and the lasting advantages of a sustainable work environment.