Imminent collapse of wood structures affected by decay

Imminent collapse due to wood decay has become an issue in Washington State, USA. Insurance companies are spending huge sums of money to repair existing wood framed buildings (both multi-family condominium and apartment buildings as well as low-rise commercial buildings and single-family residences) due to case law on the subject of imminent collapse. Typically collapses occur when the structure can no longer support the imposed loads. The cause of these collapses is normally easy to identify due to the combination of the weakened structure (or element of the structure) with a significant event exceeding the capacity of the structure such as a natural hazard (snow, wind, earthquake, etc.) or man-made hazard (improper use, construction activity, alteration). However, collapses often occur when the structure is not loaded with live loads. These types of spontaneous collapses result in extensive studies in order to attempt to determine the cause of the collapse. Most structures (if protected and maintained) including wood frame buildings, can last indefinitely. However, within the last 20 years the combination of modern architectural design, energy conservation methods, new building materials and new wall cladding systems have reduced redundant water resistant features previously present that provided protection for the structure. Thus, wood decay (rotting) of a wood structure, which previously may have taken many years or even centuries in some cases to cause a building to collapse, currently initiates shortly after construction and manifests itself to the extent that portions of a building may be significantly reduced in strength within a few years.

• DEFINITIONS

• APPLICABILITY OF BUILDING CODES

• DECAY

• SOURCES OF WATER INFILTRATION

• DESIGN CONCEPT

• DEVELOPMENT CULTURE

• CONCLUDING REMARKS

• REFERENCES