Re-Structure-ing History

631 N. Broad

The City of Philadelphia is rich with historical buildings.  From old banks to meeting houses to residential buildings that date back to the beginning of our country, it is hard to find a street in the City of Brotherly Love without a historic landmark or building.   This is one reason why Bala is no stranger to working on historic buildings.  Instead of starting from scratch, developers are inspired to work within the confines of these old buildings to breathe new life into structures rich with stories and character.  The Stable Lofts on North Broad Street is one of these landmarks. 

The building, built in 1867, was originally home to the Edwin Hart Stable. Records indicate that this company occupied the site until around 1900, but the structure then changed purposes multiple times over the next 100 years.  The building has served as a motor car company, a gas tank distributor, a sewing machine company, a pharmaceutical lab, a hosiery company and, most recently, an art gallery.  

Seeing the growth potential on the North Broad Street corridor, North Broad Living Management purchased the historic building to convert it into a new boutique-style residential building with a shared roof deck and 5,000 square feet of ground floor retail. The developer retained Canno Design as the architect and brought Bala on as the structural and MEP/FP engineer for the adaptive-reuse project. 

One of the biggest challenges of this adaptive reuse project was designing a new structure within the building and retaining the existing exterior masonry walls to preserve the outward appearance and history of 631 North Broad Street.  The developer further wanted to expand the number of residences they could fit into the building, so they needed to build vertically from the original three-story structure.  The project took on a three-pronged approach including structural temporary bracing of exterior brick masonry walls, structural demolition of existing interior structures and a new steel frame for the building.  Bala’s structural team devised a strategy to use the new steel frame as part of the temporary one to brace the exterior brick masonry walls and allow for the safe demolition of interior structures.  New foundations were poured, and new steel columns were needled through the existing structure.  Primary steel girders were installed to brace the columns at the new 2nd and 3rd floor levels.   

Since the existing 3rd floor had to be replaced at the same elevation; a detailed, phased construction sequence was designed.  Using the existing 3rd floor as a platform, steel erectors installed a new frame 3 feet above the existing floor.  Branching off this steel frame, like the limbs of a tree, steel outriggers anchored a continuous steel channel to the existing masonry wall.  After the walls were braced, the cast-iron columns, heavy timber girders and wood roof trusses, plus the wood floor and roof framing were safely removed from the interior of the building.  With the interior structures removed, the balance of the new steel frame was erected and permanently attached to the exterior walls. 

Although challenging to design, making use of all the historic buildings Philadelphia has to offer allows the city to keep its deep-rooted character while continuing to revitalize the region. Bala has designed over 50 adaptive-reuse projects and we look forward to reimagining these historic places so that they can continue to thrive in the future.    

Developer: North Broad Living Management 
Architect: Canno Design 

 

To learn more about the project, please visit our project write up here.   

Authors

Terence F. Mascitelli, PE
Structures Project Manager