This Guide addresses flanking transmission of sound through wood framed construction. Continuous structural elements and connections at the junctions of partition walls and floors provide transmission paths that by-pass the separating partition between two noise-sensitive spaces. Flanking transmission is sound transmission between two rooms by paths other than directly through the nominally separating wall or floor assembly. Flanking exists in all buildings and its importance in determining the apparent sound insulation (that perceived by the occupants) depends on of the construction details of the walls, the floors and their junctions. This Guide is the derivative of four industry-sponsored research projects conducted at IRC/NRC. The focus and construction details were decided by a Steering Committee of technical representatives from each of the supporting partners. Partners included Canada Mortgage and Housing Corporation, Forintek Canada Corporation, Marriott International, National Research Council Canada, Owens Corning, Trus Joist, and USG. This Guide supersedes the version published in 2005. This version includes estimates of the flanking due to directly attached gypsum board on ceilings, corridor walls, and exterior walls. (The first version assumed that these surfaces were mounted on resilient channels, and thus had negligible effect.)Overview of Content and Intended Application The intent of this guide is to present the findings from a substantial experimental research study, in a form that can be used as a framework for design. The guide focuses on wood-framed assemblies because that was the priority of the study on which it is based. Other types of walls and floors with concrete or steel structural assemblies also have significant reduction of sound isolation due to flanking, but they are outside the scope of this guide. The experimental study included only a limited set of constructions. Specific constraints imposed on the research specimens are discussed further in the section on performance of typical assemblies. Many materials and many construction details were kept constant, to avoid masking the effect of the systematic modifications. As a result, clear and consistent trends could be associated with specific construction changes, but it must be recognized that the results may not capture the effect of all significant variants. To show trends clearly, and to provide a framework for design estimates, expected sound transmission ratings are presented for each construction. For a number of specific cases, detail drawings and specifications including identification of specific proprietary materials are presented, and these are documented further in a detailed report [1]. Although it is not repeated at every step of this guide, it should be understood that some variation is to be expected in practice due to  changing specific design details, or poor workmanship, or substitution of “generic equivalents”, or simply rebuilding the construction. Despite this caveat, the authors believe that trends shown here do provide a good estimate of the flanking in typical wood-framed constructions.