What Coping Stones Do — and Why They Fail
Coping stones are the flat capstones set on top of parapet walls, retaining walls, and garden walls. Their job is to shed water to both sides — away from the building face and away from the wall itself. When copings work correctly, rainwater runs off and drips clear of the wall. When they fail, water cascades directly down the brick face and into mortar joints.
Coping stones fail in three ways: the mortar joints between them crack and open (allowing water to enter from above), the stones themselves crack from thermal cycling, or they shift and displace from freeze-thaw movement of the substrate below.
Coping Materials in NYC
- Bluestone — most common coping material on pre-war NYC buildings; sourced from regional quarries
- Limestone — used on many rowhouses and apartment buildings matching brownstone-era construction
- Precast concrete — used for new construction and replacement on non-landmark properties
- Brownstone — repair and replacement on existing brownstone copings using matched material
Our Coping Stone Process
- Inspect all coping stones — assess cracking, displacement, and joint condition
- Source replacement material matching existing as closely as possible
- For LPC properties: submit material samples for commission approval before installation
- Remove failed coping stones carefully
- Prepare parapet top surface — clean, level, apply waterproofing membrane to top of wall
- Install new coping stones with correct mortar, proper slope for water shedding
- Point all coping joints with appropriate mortar or sealant
LPC Requirements for Coping Work
On landmark properties, coping material must match the original. Limestone coping cannot be replaced with precast concrete without LPC approval. We prepare material samples for LPC review when required and source appropriate historic materials for properties across all four boroughs.