How to Detail Drainage Mat with Stucco

Cladding Water Management

Course Description

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.

Course Instructor Christine Williamson

Course Length 7:00

Published 06 May 2022

Keywords: drainage, water resistive barrier, stucco cladding, water management


About Building Science Fight Club

Christine Williamson - Assoc. AIA

Building Scientist | Instructor

Christine Williamson has spent her career in building science forensics, discovering why buildings fail and working with owners, architects, and builders to remedy the problems. She is the founder of the Instagram account @BuildingScienceFightClub, an educational project that teaches architects about building science and construction.