Structural Engineers

Structura was brought in to assist with the design and construction of a 20 unit, multi-family residential apartment building located between two existing buildings. The building features four levels as well as a cellar, plus a roof patio and green roof. Floors are framed with pre-engineered open web wood trusses supported on wood stud bearing walls.

The Challenge

There were two notable challenges associated with this project. First, the cellar level of the new building is lower than the foundations of the two existing adjacent buildings, creating challenges with the new exterior foundations. Also, the lateral design for the north-south direction was a challenge since there are very few load-bearing walls that stack for the entire height of the building.

The Solution

To address the issue with the exterior foundations, Structura’s design called for underpinning the existing adjacent building foundations down to the depth of the new building wall foundations, as well as temporary support during excavation–without crossing the property line–for portions of the building that do not abut an existing building.

To respond to the challenge of the lateral design in the north-south direction, Structura was able to cantilever the diaphragm off of the central CMU stair and elevator shafts instead of resisting the force through load-bearing wood walls.

The Takeaways

Each force imposed on the building must have a clear load path from the point of loading to the foundation of the structure. This is a leading concept that drives structural design. Although there were certain limitations in place, Structura was able to analyze the structure and determine a solution for the foundation and lateral design that satisfied the overall design intent without compromising the structural integrity of the building.