By Justin Henshell, FAIA, FASTM
This is part two of a two-part series on waterproofing membranes under green (garden) roofs. The first part, published last month, traced the history of waterproofing membranes under plazas and earth-covered, below-grade spaces, and discussed the various types of waterproofing systems currently marketed and their advantages and disadvantages for use under green roof systems. This part covers the attributes of candidate membranes and offers a list of minimum physical properties proposed to satisfy the specific needs for those membranes exposed to continuous moist environments, aggressive chemicals, root invasion, and abusive maintenance. Additionally, it discusses failures and offers case studies to illustrate them.