Designing for Durability

Strategies for achieving maximum durability with wood-framed construction
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Sponsored by Think Wood

Learning Objectives:

  1. Analyze factors contributing to the long-term durability of wood buildings.
  2. Implement effective design strategies for controlling moisture in wood buildings.
  3. Discuss comprehensive approaches for protecting wood buildings from insect damage.
  4. Determine effective quality control measures that will have significant positive long-term impact on building durability.

Credits:

1 AIA LU/HSW
1 GBCI CE Hour
1 AIC CPD
0.1 IACET CEU*
1 PDH*

Architects specify wood for many reasons, including cost, ease and efficiency of construction, design versatility, and sustainability—as well as its beauty and the innate appeal of nature and natural materials. Innovative new technologies and building systems are also leading to the increased use of wood as a structural material, not only in houses, schools, and other traditional applications, but in larger, taller, and more visionary wood buildings. But even as the use of wood is expanding, one significant characteristic of wood buildings is often underestimated: their durability. Misperceptions still exist that buildings made of materials such as concrete or steel last longer than buildings made of wood. Although this connection between materials and building longevity is often assumed, it is not borne out in fact, as will be discussed in this course.

Examples of wood buildings that have stood for centuries exist all over the world, including the Horyu-ji temple in Ikaruga, Japan, built in the eighth century, stave churches in Norway, including one in Urnes built in 1150, and many more. Today, wood is being used in a wider range of buildings than would have been possible even 20 years ago. Next-generation lumber and mass timber products, such as glue-laminated timber (glulam), cross laminated timber (CLT), and nail-laminated timber, along with a variety of structural composite lumber products, are enabling increased dimensional stability and strength, and greater long-span capabilities.

These innovations are leading to taller, highly innovative wood buildings. Examples include (among others) a 10-story CLT apartment building in Australia, a 14-story timber-frame apartment in Norway, and an eight-story CLT apartment in the United Kingdom. Closer to home, a six-story wood building (plus mezzanine and penthouse) was recently completed in British Columbia—becoming, for a moment, the tallest contemporary wood building in North America.1 Although durability is important in every structure, a long future takes on an additional dimension in iconic structures such as these.

As with any structural material, perhaps the most important single factor to a long and useful service life is effective design. Extensive research and documented experience have led to a number of proven strategies for ensuring that wood material reaches its full potential for longevity. This course outlines the informed design, specification, detailing, and quality control during construction, installation, and maintenance that are collectively key to achieving maximum durability in today’s wood construction.

Maple and Terry Halls
University of Washington 
Seattle, WA
Completed in 2015, this 440,000-square-foot student housing project includes two residential buildings, each with five stories of wood-frame construction over a concrete plinth with below-grade parking.

Photo: Mithun Architects Inc., WG Clark Construction

Maple and Terry Halls University of Washington Seattle, WA Completed in 2015, this 440,000-square-foot student housing project includes two residential buildings, each with five stories of wood-frame construction over a concrete plinth with below-grade parking.

 

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Originally published in Architectural Record

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