Throughout history, wherever wood has been available as a resource, it has found favor as a building material for its strength, economy, workability and beauty, and its ability to last has been demonstrated again and again. From the ancient temples of Japan and the great stave churches of Norway to the countless North American buildings built in the 1800s, wood construction has proven it can stand the test of time. The art and technology of wood building, however, has been changing through time. Can modern wood-frame buildings perform as well?

Protection of buildings from moisture is an important design criterion, as important as protection from fire or structural collapse. Designers, builders and owners are gaining a deeper appreciation for the function of the building envelope (exterior walls and roof). This includes the performance of windows, doors, siding, sheathing membranes, air and vapour barriers, sheathing, and framing. The capabilities and characteristics of wood and other construction materials must be understood, and then articulated in the design of buildings, if proper and durable construction is to be assured.

This guide will help design and construction professionals, and building owners understand moisture issues related to the design and construction of wood-frame buildings. The primary objective is to provide ideas and solutions to ensure wood-frame buildings perform as expected. The primary focus of the guide will be on the control of rainwater penetration in exterior walls, particularly for climates subject to high moisture exposure.