• Water runoff caused the limestone face to delaminate on an arch originally part of a 1947 landmark building at Princeton University. This deterioration had been patched in an earlier restoration with mortar and wire reinforcement. Unfortunately, the repairs did not hold.A detailed study of the existing arch construction was made and investigation probe holes were opened within the wall. Further openings during construction indicated that additional temporary shoring was required to support the steel beam. Unfortunately, the available space for shoring and work platforms was very limited. A steel tube was installed across the stone masonry. This steel tube was designed and detailed by the engineer to limit its deflection so that the stone masonry wall it supported would not crack.
  • The contractor constructed a lightweight and elegant falsework from plywood and 2x4s. The plywood falsework served two purposes. First, it was used to dismantle the existing deteriorated limestone arch. Later, it was used to install the new limestone arch units after the new column units' installation.
  • The crew installed the new limestone units using stainless steel pins and dry pack mortar so that each unit was tied to an adjacent limestone unit. In setting the limestone arch units, the contractor used rope filler at the toe of the joints so that the final mortar tooling could be performed by hand. The rope was installed against the falsework when the mortar joints were filled.
  • The crew removed the falsework a second and final time and mortared the limestone units on the bottom after removing the rope filler.
  • The masonry wall directly above the arch, on both the inside and outside faces, received new irregular shaped schist stone. The schist masonry completed the project.

The masonry wall had face masonry units and header units. Mortar joints in the masonry schist are a special mix having a color and texture matching the original building mortar joints.The masonry contractor had difficulty setting the units. His crew needed to make minor adjustments in the joint angles. The fabricator sent a stonecutter to the site to provide additional angle to the units that were originally provided. Field corrections were easily provided due to the limestone's softness.The arch was constructed using solid limestone units with the same ornamental details as the original arch units. This reconstruction improved on the original construction because the original construction used a face limestone unit installed over the lower arch units. This assembly was reconstructed with one unit. This should provide greater longevity because of less mortar joint exposure. The arch unit size was increased, but the contractor provided a quality finished product.