Summary

In 2005, the OAA Council approved in principle a “Wall Design Exclusion” in order to protect the Indemnity Plan (now Pro-Demnity Insurance Co.) from the alarming number of claims related to some exterior wall systems. At the same time, Council saw the need to support its members by providing appropriate information, in the form of a resource, which would assist architects and their practices to understand the underlying principles of rain penetration in walls. This resource would be a valuable tool that would better enable members to develop wall systems and details that conform to good practice techniques, resulting in the design and delivery of appropriate exterior wall assemblies. By so doing, many potential claims would be avoided. The resulting resource is called the Rain Control Practice Guide.

Background

1. The Rain Control Practice Guide is both a technical and practical resource aimed at architects and architectural practices. It explains some principles and techniques involved in the control of rain in exterior building wall assemblies, but it is not comprehensive. It also provides a classification system for dealing with different wall types and provides examples showing different wall types and surface materials.In addition, the Guide contains a series of typical details demonstrating the principles of good wall design practices. These are part of the Guide document, but may also be downloaded from the OAA web site in “dwg” format for use on AutoCAD or compatible software.
2. The Rain Control Practice Guide provides elements necessary to understand and deliver appropriate exterior wall systems for various building situations. It addresses the Indemnity Plan “Wall Design Exclusion” by providing the basis for the design of many wall systems.
3. The Indemnity Plan “Wall Design Exclusion” affects all designs commenced on or after July 1, 2002. It is therefore important that all practices understand the issues and are able to deliver appropriate exterior wall systems.
4. Dr. John Straube, affiliated with the Civil Engineering Department and the School of Architecture at the University of Waterloo, authored the Rain Control Practice Guide. Dr. Straube teaches in the area of building materials and detailing.

Procedure

1. If you or your practice are involved in the design and detailing of exterior wall systems, then you need to understand and follow the principles of the Rain Control Practice Guide in the selection, design, detailing and execution of exterior wall systems. It is also important to ensure that others in your practice who have responsibilities in this regard are equally aware of these issues.