IN PREPARATION OF THIS CHAPTER, THE CONTENTS of the fourteenth edition were drawn upon. The authors acknowledge the author of the fourteenth edition, Wayne Ellis (Deceased). The current edition will review and update the topics as addressed by the previous author, introduce new technology that has been developed, and include up-to-date references. Other chapters in this manual cover the influence of water on the formulation and durability of organic coatings. Recent ASTM publications about the moisture effects in building materials are listed in the Bibliography at the end of this chapter. These publications describe moisture problems and solutions involving coatings and their uses. Although this chapter is intended to describe only the principal testing and evaluation of water resistance, some general remarks may be helpful in understanding the test conditions.