Preventative Maintenance Helps Preserve Pennsylvania Landmark

Project Background

• PPL (formerly Pennsylvania Power and Light) completed construction of its 23-story corporate headquarters in Center City Allentown in 1928
• The transitional masonry building has a steel frame embedded in its brick exterior walls; its bottom two floors have a limestone veneer featuring several bas-reliefs by Alexander Archipenko
• MPS began working with PPL in 1985 and has completed over 70 projects for PPL since that time, with ongoing maintenance continuing in staggered phases

Project Challenges

• The PPL Building has remained fully functional throughout all maintenance work, with much of the noise-generating activity completed on weekends
• The installation of flashing at the rising walls required the removal of the outer two wythes of brick to provide adequate performance
• Narrow setbacks on the upper-level roofs made installation of scaffolding very difficult
• All window lintels, which MPS replaced, were embedded in brick pilasters on both sides of the windows; these large pilasters extend out over three feet from the face of the building
• New limestone pieces were used in lieu of brick at the window lintels to provide an updated look to the building

Project Approach

• Corrosion of the embedded steel columns in the upper-level masonry walls caused cracking and displacement of the brick veneer; steel was exposed, cleaned, and coated with a rust-preventative coating system
• Window lintels were corroded due to a lack of flashing; MPS replaced all window lintels with new properly flashed galvanized steel lintels
• Water was entering the building walls through the joints in the large limestone copings; MPS removed the copings, installed proper through-wall flashing, and reset the copings
• Rainscreens were installed to protect the inboard sides of the parapets from wind-driven rain while allowing the parapets to dry; rainscreens were tied into the coping flashing to provide continuous protection
• Improper flashing at the masonry rising walls was allowing water to enter the building at each of the upper-level roofs; MPS installed new two-wythe-deep flashing at each rising wall