Cathedral Basilica of Saints Peter and Paul

Philadelphia, PA


The Cathedral Basilica of Saints Peter and Paul in Philadelphia was designed by John Notman and Napoleon LeBrun and constructed between 1846 and 1864. The exterior walls are load-bearing masonry, with brownstone cladding. The copper-clad dome rises from the crossing of the Cathedral, with the top of the dome approximately 200 feet above the ground. A sheet copper spire surmounted by a gilded orb and cross sits atop the dome. The existing copper cladding was purportedly installed in the 1950s to replace an earlier copper cladding of the dome, which in turn replaced the original tin cladding at the dome of the Cathedral.

The copper dome is comprised of 12 facets, which are divided by large vertical ribs. In between the vertical ribs are sheet copper pans of the dome cladding, which have folded horizontal seams. The pans extend vertically up the dome 27-1/2 inches high from seam to seam, as determined at several locations along the height of the dome. The vertical seams between the pans are covered by trapezoidal vertical ribs. Near the bottom of each facet is an arched top window with copper clad frame and sash.

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Scope of work

  • Investigated and documented the existing conditions of the exterior copper cladding on the dome, spire and drum.
  • Measured the thickness of the copper cladding on the dome using a StressTel TM1-CD Ultrasonic Thickness Gauge.
  • Provided high definition live-feed video to project team during inspection of representative areas.

Original architect

  • John Notman and Napoleon LeBrun (completed 1864)

Building owner

  • Archdiocese of Philadelphia

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