ABSTRACT
Moisture in buildings that accumulates on moisture-sensitive materials behind walls, roofs, and other areas that can trap water is a source of signicant damage to buildings, including mold formation and structure rot. While there are many recognized sources of moisture intrusion in buildings, one of the most critical is the interface between the wall and openings in the wall associated with fenestration products (windows and doors). Figure 14.1 gives examples of the types of damage that can occur to buildings around window openings if they are improperly installed or ashed. A report by RDH Building Engineering Limited in Canada studied the occurrence of leakage for a wide variety of window types and assemblies, considering six potential leakage paths for water intrusion [1]. Although water leakage was found to some extent in all of the leakage paths, the “through window to wall interface to adjacent wall assembly” was the most prevalent leakage path for all types of windows tested and had a high risk of consequential damage to the building. Improper use of ashing and the overreliance on building sealants were consistently noted as key contributing effects in this report. Another report by the Partnership of Advancing Technology in Housing (PATH), which publishes the Durability by Design Guideline, noted that “most leakage problems are related to improper or insufcient ashing details or the absence of ashing” [2]. The PATH report also noted that “caulks and sealants are generally not a suitable substitute for ashing.”
