The Cathedral of St. John the Divine in Morningside Heights, New York City is one of the largest Gothic cathedrals in the world and a New York City Landmark. Graciano Corporation performed masonry restoration at the Cathedral, addressing the full range of conditions found on a large Gothic stone structure: repointing, stone replacement, cleaning, Dutchman repairs, brick replacement, and surface rehabilitation using multiple cleaning methodologies.
Scope of Work
The restoration encompassed stone masonry, brick masonry, and cleaning work across multiple elements of the Cathedral exterior.
- Unit stone replacement
- Stonework
- Stone patching
- Stone facade pinning
- Dutchman repair
- Repointing masonry
- Individual brick replacement
- Brickwork
- Lintel replacement
- Pressure washing
- Chemical cleaning
- Alkaline cleaners
- Acidic cleaners
- Abrasive cleaning
- JOS and TORC cleaning
- Poultices
- Paint removal
- Masonry cleaning
- Masonry surface rehabilitation
About the Project
The Cathedral of St. John the Divine is constructed primarily of granite and limestone and features elaborate Gothic ornament, including sculpted stone portals, flying buttresses, and figurative stonework. Restoration at a building of this complexity requires both traditional masonry skills -- hand tooling, Dutchman replacement, and precision repointing -- and proficiency with specialized Gothic stone restoration techniques.
Cleaning Gothic stone requires careful selection of methods suited to the specific staining and substrate conditions. The Cathedral project used JOS (a controlled micro-abrasive system), TORC (a swirling water and fine aggregate system), chemical cleaning, poultices, and pressure washing depending on location and surface conditions. These methods allow effective cleaning without damaging the historic stone substrate or carved ornament.
Dutchman repair -- the insertion of a new stone unit into an existing masonry surface to replace a failed area -- is a technique Graciano has used on dozens of historic stone buildings in New York City and across the region. At the Cathedral, Dutchman repairs addressed localized deterioration in carved and plain stone members while preserving the continuity of the original masonry fabric.
Cleaning Methods Used
- JOS system: Fine aggregate in a controlled air-and-water stream; suited for carved ornament and delicate stone surfaces
- TORC system: Water and aggregate in a swirling pattern; effective for general surface soiling on stone
- Poultices: Used for targeted stain removal from localized deposits on stone faces
- Chemical cleaners: Alkaline and acidic formulations selected by staining type and substrate
- Pressure washing: Applied at controlled pressures appropriate for the stone assembly