Terra Cotta Repairs

During a recent project meeting, the team and I were discussing terracotta and prior repair campaigns - mainly to try and understand current inspections and work contemplated in comparison to past projects where significant expense was incurred on the seemingly same repairs.

Project analysis is becoming increasingly more important to mitigate future risk by understanding past practices so that new strategies can be developed to ensure current repairs have greater longevity.

The Center for Architecture has an excellent presentation on terracotta entitled, Historic Terracotta: Stabilize, Restore or Replace (5/7/18). The presentation is amazing, however, by far (in my opinion) was Timothy D. Lynch PE presentation from a DOB Perspective (at the time, Mr. Lynch was Chief Engineer Enforcement Bureau). Some highlights are below.

DOB - MAINTENANCE & SAFETY ISSUES

Mr. Lynch started the presentation noting that terracotta although beautiful and widely used is challenging from a maintenance and safety standpoint. He noted minimum standards for terracotta and the application of prescriptive and performance requirements (which form construction code) and the fact that there are no maintenance codes.

Mr. Lynch presented a slide from § 28-101.2 "Building Code Intent" which speaks to minimum requirements and standards based on current scientific and engineering knowledge, experience and techniques, and the utilization of modern machinery, equipment, materials and forms and methods of construction, for the regulation of building construction in NYC and in the interest of public safety.

Most interesting was the discussion around how performance specifications are developed when a building is built by professionals and material manufacturers. The snag he noted was that exterior materials (like terracotta) have a long shelf life which outlasted the original architectural and construction teams, however over the course of the their life have been slowly degrading causing maintenance requirements that must still meet minimum standards per Code. He discussed "Condition vs. Time" and how materials degrade over time and the factor of safety. He noted that terracotta has a high factor of safety, however, the dilemma with it is that over time the factor of safety declines thorugh age of material or corrosive inserts.