Evolution of Sheet Metal Window Sill Flashing: Lessons Learned that Lead to Better Performance

This presentation initially took place at IIBEC's 2022 International Convention and Trade Show in Orlando, Florida.

Flashings are often the most challenging aspect of aluminum window system design and installation on both new and replacement projects. Although the aluminum window system and its performance are often well detailed by the window manufacturer, providing a waterproof transition of the window frame to cladding system interface can be challenging. Metal sill flashings have been used in the construction industry as a supplemental element in window systems (in addition to the manufacturer’s standard sill design). However, inadequate attention to sill flashing detailing can result in water leakage into the exterior enclosure and even into the building interior. Historically, metal sill flashing was often continued into the rough opening of the window, and this method is sometimes still used today. This presentation addresses how going beyond the standardized approach to detailing, and taking into consideration the installers’ sequencing of components during installation, can minimize potential pathways for water intrusion.

Rocco C. Romero, AIA, NCARB
Wiss, Janney, Elstner Associates Inc. | Seattle, WA

Rocco C. Romero is a registered architect and principal with Wiss, Janney, Elstner Associates Inc. (WJE) in Seattle, Wash. He has more than 30 years of experience and has investigated hundreds of building enclosure systems. Romero specializes in water leakage investigations, assessment, diagnostic testing, and repair design and construction document preparation in contemporary and vintage buildings and structures. He provides professional consulting services to owners, architects, and general contractors related to the design, performance, and constructability of new and retrofit building enclosure systems. Romero also provides expert witness and litigation support services on existing buildings.