Many decades of engineering service have been provided for the ongoing stabilization and restoration of Independence Hall, with all efforts designed to minimize impact to, and loss of, historic building fabric.
Independence Hall was built in 1732 as the Pennsylvania State House. Within its walls, the Declaration of Independence was signed and the United States Constitution was debated and drafted. The World Heritage Site is visited annually by over a million guests.
Keast & Hood provided structural engineering during the formative years of Independence National Historical Park. The highlight of this work was the opportunity to work closely with some of the pioneering architects of the National Park Service, refining techniques that evolved into the Secretary of the Interior’s Standards for Historic Preservation. The basic approach was to allow Independence Hall’s original structural system to remain in place, but supplement and strengthen it where necessary with modern structural materials.
Work continued with the Independence Square utilities improvement project, which involved routing and supporting new electrical, plumbing, fire safety, security, and HVAC equipment within the sensitive environment of Independence Hall. The project included a condition assessment of the original timber frame structure and its 175-foot high tower. Particular attention was given to detecting concealed internal decay in the heavy timbers, using core-sampling and non-destructive stress wave testing. The steeple was strengthened by installing a new internal steel tower designed to fit within the framework of the historic timber structure.
Ongoing preservation and preventive care included preparation of an Historic Structure Report detailing the condition, history, and origins of William Strickland’s 1828 tower siding assembly. Thick siding planks are connected internally by, and reinforced with, vertical iron rods. Replacement of a single board requires disassembly of the entire wall. Non-destructive X-ray and resistance drill tests uncovered historic graffiti and assessed the condition of the rods and wood. A full-scale mockup was built to identify the least-destructive methods for disassembly, removal of deteriorated elements, and reconstruction. Repairs included selective wood replacement and replacement of the deteriorated original wrought-iron weathervane support spindle with stainless steel.
Restoration of Independence Hall Tower earned a 2012 Grand Jury Preservation Achievement Award from the Preservation Alliance for Greater Philadelphia.
Many decades of engineering service have been provided for the ongoing stabilization and restoration of Independence Hall, with all efforts designed to minimize impact to, and loss of, historic building fabric.
Independence Hall was built in 1732 as the Pennsylvania State House. Within its walls, the Declaration of Independence was signed and the United States Constitution was debated and drafted. The World Heritage Site is visited annually by over a million guests.
Keast & Hood provided structural engineering during the formative years of Independence National Historical Park. The highlight of this work was the opportunity to work closely with some of the pioneering architects of the National Park Service, refining techniques that evolved into the Secretary of the Interior’s Standards for Historic Preservation. The basic approach was to allow Independence Hall’s original structural system to remain in place, but supplement and strengthen it where necessary with modern structural materials.
Work continued with the Independence Square utilities improvement project, which involved routing and supporting new electrical, plumbing, fire safety, security, and HVAC equipment within the sensitive environment of Independence Hall. The project included a condition assessment of the original timber frame structure and its 175-foot high tower. Particular attention was given to detecting concealed internal decay in the heavy timbers, using core-sampling and non-destructive stress wave testing. The steeple was strengthened by installing a new internal steel tower designed to fit within the framework of the historic timber structure.
Ongoing preservation and preventive care included preparation of an Historic Structure Report detailing the condition, history, and origins of William Strickland’s 1828 tower siding assembly. Thick siding planks are connected internally by, and reinforced with, vertical iron rods. Replacement of a single board requires disassembly of the entire wall. Non-destructive X-ray and resistance drill tests uncovered historic graffiti and assessed the condition of the rods and wood. A full-scale mockup was built to identify the least-destructive methods for disassembly, removal of deteriorated elements, and reconstruction. Repairs included selective wood replacement and replacement of the deteriorated original wrought-iron weathervane support spindle with stainless steel.
Restoration of Independence Hall Tower earned a 2012 Grand Jury Preservation Achievement Award from the Preservation Alliance for Greater Philadelphia.
CLIENT: National Park Service | Bargmann Hendrie + Archetype, Inc.
LOCATION: Philadelphia, PA
TYPE: Cultural, Government, Historic, SERVICES: Historic Preservation, Renovation, Structural Intervention, MATERIALS: Heavy Timber, Masonry, Steel, Wood, SUSTAINABILITY: . . . . . . . . . . . . . . . . . . . . . . . .
Completed project photography © Jeffrey Totaro
