Structural Enhancement

19th century Mercantile building required significant bracing and support, as well as a new floor, but is a shining and visible example of Urban Rehabilitation.

By D. Matthew Stuart, P.E., S.E., F.ASCE, F.SEI, SECB, MgtEng

The Columbian Building was a facility in need of rehabilitation. One of the key structures in Newark’s “Four Corners” historic district, it is located in the city’s traditional center for commerce and business. The existing structure, originally constructed in 1890, was a run-down five-story mercantile loft with timber floor framing and brick masonry bearing walls. Hanini Construction hired Pennoni Associates to provide structural design services to rehabilitate the building into a mixed-use facility that includes a restaurant and residential units. Structural renovations included documenting and implementing the necessary structural repairs, the installation of new lateral strengthening, and the addition of a new sixth floor and high roof structure, as well as several significant structural modifications to accommodate the required restaurant fit-out. 

The Columbian Building consisted originally of two separate but adjacent mercantile loft structures that were modified to appear as one single building at some time during the life of the facility. This was done by constructing a front façade that made the location appear to be one building. All other structural facets of the building, however, were indicative of two separate adjoined buildings, including load bearing masonry brick party walls between the two buildings and the adjacent buildings. During the latter half of the 20th century, the adjacent buildings on the east side of the Columbian Building were demolished to allow for the construction of the New Jersey Devils Plaza, an open air, ground level promenade between the Prudential Center and Market Street. This urban renovation project left the east five-story wall of the Columbian Building exposed. On the west side of the building, the existing adjacent neighboring building was not constructed as high as the Columbian facility, so the upper portion of the west elevation of the original building was exposed. 

Mercantile loft structures constructed in the United States in the 19th and early 20th centuries were narrow, two- to 7-story buildings with longitudinal load bearing brick masonry walls and transverse, clear span, framed wood floors and roofs. Typically the load bearing walls between adjacent buildings were party walls, meaning both adjacent structures used a single shared wall for the support of the floor and roof framing. In addition, in some cases, and as was done in the western side of the Columbian Building, a longitudinal cast-iron column and wrought iron or steel beam line provided interior support for at least two bays of transverse framed wood floors. Lateral stability of these multistory buildings was provided by the longitudinal brick load bearing shear walls. However, in the transverse direction typically no distinct lateral resisting system was provided other than rear and front masonry walls with punched window openings that often also included large, ground floor, and storefront openings. Additional transverse lateral support was also typically provided by the contribution of similarly constructed and immediately adjacent mercantile loft structures. 

In the case of the Columbian Building, the only transverse lateral resisting system that was present prior to the renovation was the rear or south walls of the facility. These were separate and distinct walls for the eastern and western halves of the two original adjoined buildings. With the demolition of the original neighboring buildings on the east side of the site, the only other existing transverse lateral resisting system prior to the renovation project was the lower neighboring building located on the west side of the structure. This existing deficient transverse lateral resisting system was further complicated by the presence of large ground floor openings in the rear walls that had been infilled with masonry brick and concrete block at some time during the life of the building. In addition, due to the kitchen and restaurant renovations proposed for the building, these same existing infilled walls were to be modified and enlarged. The longitudinal stability of the existing buildings, which was more than adequately provided by the longitudinal load bearing brick masonry party walls, was also partially compromised by the introduction of numerous punched window openings at each level as required to complete the desired adaptive reuse transformation of the building. All of the above existing building deficiencies and renovation challenges were also further complicated by the desire to add an additional sixth floor to the building. Pennoni addressed and successfully developed practical, constructible and economical solutions to these challenges. 

Strong basis 

Engineers conducted an analysis of the existing structure to determine the existing building structural capacity based on information gathered during field investigations, material testing, and historic design references. The analysis determined that the existing bearing walls and foundations had adequate capacity to support the new sixth floor and high roof structure. This conclusion stemmed from comparing the original wall loading, based on the existing floor framing capacity, to the new intended loading of the bearing walls. Engineers determined that the new loading conditions with the additional sixth floor and high roof was lower than the original loading of the building and therefore the bearing walls had adequate capacity to support the new addition. The scheme required strengthening of the existing timber framing at isolated locations to satisfy the new restaurant loading requirements. In addition, several deficient existing framing conditions required structural repairs or replacement. 

Due to significant modifications of the existing exterior longitudinal brick masonry walls, engineers determined that additional steel framing was required to re-support the existing gravity floor framing as well as provide lateral stability for the existing structure. The modification to the existing exterior walls included the introduction of multiple new punched window openings in the exposed sides of the building and the elimination of existing infill masonry shear walls at the ground floor at the rear of the building. The new structural steel framing consisted of HSS columns with wide flange beams installed directly beneath the existing flooring framing. Vertical X-bracing was installed to provide the longitudinal lateral stability that was compromised by the introduction of the punched openings. Diaphragm connections at the rear and side walls were designed to enhance the existing deficient shear transfer conditions and transverse lateral stability of the building. The steel columns and vertical X-bracing continued to the basement, where they were supported by a cast-in-place concrete shear wall. At the rear wall a new cast-in-place concrete infill shear wall was designed and constructed to compensate for the existing deficient masonry infill wall condition as well as the new openings required for the kitchen and restaurant. 

New heights 

The new sixth floor and high roof structure consisted of a steel and wood framed floor and roof members. The new sixth floor also required the complete demolition and reconstruction of the remaining original roof structure that had exhibited considerable deterioration prior to the renovation project. Rooftop steel dunnage became necessary to support the large restaurant mechanical rooftop units. The structural re-support of the brick masonry parapet and cornice was also necessary due to the new sixth floor roof terrace elevation. 

The restaurant fit-out required several modifications to the existing structure to accommodate the open-space layout required for dining, including a transfer condition of the existing interior load bearing masonry wall. This was accommodated by installing structural steel channels, bolted on each side of the existing brick masonry bearing wall that spanned between new HSS steel columns. Additional work included the re-support of the existing framed brick arch alleyway structure above the basement area and the re-support of existing steel girders due to interferences with new stair clearances. 

The challenges encountered and the innovative yet non-intrusive structural solutions developed for this project serve as a model for how to best renovate and structurally upgrade a typical 19th Century mercantile loft building. In addition, because some of the structural modifications, such as the vertical X-bracing and new longitudinal steel support beam framing, were left exposed in the public restaurant areas of the building, the general public has an opportunity to observe and identify visually these very same modern day solutions juxtaposed against the contrasting exposed original modified masonry wall and wood framed construction. 

The adaptive reuse of existing buildings is an excellent example of sustainable design and was recognized by Preservation Green Lab of the National Trust for Historic Preservation as having many environment and economic benefits in a 2012 report entitled; “The Greenest Building: Quantifying the Environmental Value of Building Reuse.” This report included a number of key findings, including: 

• Reuse matters: Building reuse typically offers greater environmental savings than demolition and new construction.
• Scale matters: Collectively, building reuse and retrofits substantially reduce climate change impacts. 
• Design matters: The environmental benefits of reuse are maximized by minimizing the input of new construction materials. 
• The bottom line: Reusing existing buildings is good for the economy, the community and the environment. 

The renovation and adaptive reuse of the Columbian Building satisfied all of the above goals, and therefore stands as a shining example of sustainability. This project posed a number of complex existing and newly created structural challenges associated with the repair, renovation and adaptive reuse of a historic multistory mercantile loft building. Yet, the structural solutions developed for the project, as described above, included simple and constructible approaches to the challenges associated with this project. Therefore, this project serves as an excellent example of how complex problems are often best solved with the most direct, yet simple and elegant approaches.

D. Matthew Stuart, P.E., S.E., F.ASCE, F.SEI, SECB, MgtEng is the structural division manager at Pennoni Associates Inc. in Philadelphia. He can be reached at MStuart@Pennoni.com.