Skip to main content

​
Introduction

The building code has long required two layers of water resistive barrier (WRB) behind stucco claddings. What many professionals misunderstand is the purpose of the second layer: many assume that it is included for redundancy, in the event that either the first layer does not perform as intended or the stucco itself is defective and cracks excessively. But neither of these things is true! The purpose of the second layer is to prevent the stucco from adhering to the first layer. It provides a “bond break” and creates a small space for drainage and drying between the two layers. This short course explains what changed to make the inclusion of this bond break necessary, why we’re finding two layers alone are no longer adequate for certain buildings, and how to improve drainage and drying using a drainage mat. About Building Science Fight Club

​
Video: How to Detail Drainage Mat with Stucco

​
Quiz

To earn AIA Continuing Education Units (CEU), you must complete the quiz below and get all 3 questions correctly. Feel free to retake the quiz if needed. To keep learning, check out more courses in Building Science.