Durability
History has shown that, with proper design and maintenance, wood structures can deliver decades and, in fact, centuries of reliable service. The key is careful planning and understanding of environmental loads and other external factors likely to impact a building over its lifetime, which involves four main methods of control:
- Moisture control – The design of durable structures begins with an understanding of moisture loading and how it interacts with building materials. Designers must consider sources of water, how the water is transported, and how to control and remove it. Wood construction maintained at a moisture content of 20 percent or less will not decay, and decay doesn’t generally occur until the moisture content reaches 25 percent or more. When wood is protected from water or vapor condensation, and exposed to normal atmospheric conditions, its moisture content rarely exceeds 15 percent. So controlling moisture is a simple and practical way to protect against decay.
- Termite control – Moisture control also contributes to the prevention of subterranean termite attack, since termites thrive on water. Other methods include the use of barriers and bait systems supplemented by periodic inspection, which also protect against other insects.
- Use of durable materials – In some cases, architectural considerations or use exposures (e.g. ground contact or certain climatic conditions) may necessitate greater protection. Under these circumstances, naturally durable wood species or pressure treated wood may be required.
- Quality assurance – Where moisture and/or insects are an issue, quality control is especially important in constructing building assemblies to resist negative effects. Proper maintenance to keep the structure dry will also help to ensure its longevity.
The publications listed below include detailed recommendations for preventing damage from moisture and living organisms. The bottom line: wood frame structures, when designed correctly and properly maintained, can provide a long and useful service life equivalent to other common building construction materials.
Sources
- Design of Wood Frame Structures for Permanence – American Wood Council, 23 pages
- durable-wood.com – A joint project of the Canadian Wood Council and FP Innovations – Forintek Division
More Information
General Durability
- Durability and Service Life
1.5MB pdf
WoodWorks - Understanding Biodeterioration of Wood in Structures
1.5MB PDF
FP Innovations – Forintek, 26 pages - Survey on Actual Service Lives of North American Buildings
196K pdf
FP Innovations – Forintek, 9 pages - Technical Topics 052: Service Life of Oriented Strand Board
APA – The Engineered Wood Association, 2 pages - Wood Preservation in Canada
106K pdf
2006 – FP Innovations – Forintek, 15 pages
Moisture Control
- Moisture and Durability
173K pdf
Joint publication of FP Innovations – Forintek Division and the Canadian Mortgage and Housing Corporation, 4 pages - Moisture and Wood-frame Buildings
586K pdf
Joint publication of FP Innovations – Forintek Division, Société d’habitation du Québec and the Canada Mortgage and Housing Corporation, 12 pages - Southern Pine Council
Website includes information on moisture, mold and southern pine - Western Wood Products Association
Website includes information on moisture, mold and western wood products - Evaluation, Maintenance and Upgrading of Wood Structures
American Society of Civil Engineers, 428 pages, $17 for non-members
Termite Control
- Borate-treated Wood for Construction
538K pdf
FP Innovations – Forintek Division, 6 pages - Combating Termites
196K pdf
Joint publication of FP Innovations – Forintek Division and the Canadian Mortgage and Housing Corporation, 4 pages - Integrated Control of Subterranean Termites: The 6S Approach
396K pdf
FP Innovations – Forintek, 20 pages - Southern Pine Council
Includes information on termites and southern pine - Termite Control and Wood-frame Buildings
245K pdf
Canadian Wood Council, 12 pages