Wood and Timber Condition Assessment Manual: A New FPL Report


Deterioration of an in-service wood member may result from a variety of causes during the life of a structure. Periodic inspec­tion of wood used in structures is important for determining the extent of deterioration so that degraded members may be replaced or repaired to avoid structural failure.


A resistance microdrill used for inspection of a historic Civilian Conservation Corps log cabin.

Inspection professionals use a wide variety of techniques to as­sess the condition of wood in service. Visual, mechanical prob­ing, and stress wave or ultrasound-based techniques are all used either individually or in combination by inspectors. Although these techniques are based on solid technical information and supporting research, prior to publication of the Wood and Tim­ber Condition Assessment Manual in 2004, no practical, com­prehensive manual provided information on inspection of wood in service.

According to editor and Supervisory Research General Engineer Robert J. RossThe Wood and Condition Assessment Manual was prepared to address this need. The manual was prepared from numerous re­search studies, inspections, and lectures dealing with assessing the condition of in-service wood and timber. It was intended for inspection professionals. A concerted effort was made to provide clear and concise explanations of various aspects of inspecting in-service wood and timber. To this end, a number of photographs and drawings obtained from actual inspections were included.”


Rehabilitation efforts for Esterhazy Castle Sopron, Hungary, have begun. The traditional mortise and tenon timber framing system was found to be in excellent condition.

Ross goes on to say, “In preparing this second edition of the Wood and Timber Condi­tion Assessment Manual, I had three objectives: (1) to update the existing chapters to reflect advancements in inspection methods; (2) to develop new material that focuses on a wide range of new techniques and technologies that have been in­vestigated for use in assessing the condition of wood structures and provide estimates of the properties of in-service wood; and (3) to make the manual available in digital format.”

The newly published and comprehensive Wood and Condition Assessment Manual summarizes information on condition assess­ment of in-service wood, including visual inspection of wood and timbers, use of ultrasound and probing/boring techniques for inspection, and assessment of wood and timbers that have been exposed to fire. The report also includes information on assigning allowable design values for in-service wood.

The Wood and Timber Condition Assessment Manual—Second Edition is available in digital format from the  Forest Products Laboratory website.