is a registered consulting engineer and the retired vice president of quality and technical services for APA. Prior to joining APA, he was Executive Vice President of the American Institute of Timber Construction. He also spent 15 years as chief engineer and part owner of Lamfab Wood Structures, a design build firm in the Midwest specializing in the design and erection of wood-framed commercial buildings, where he was involved in the design of over 500 structures. Mr. Williamson is co-editor in chief of the McGraw-Hill Wood Engineering and Construction Handbook editor in chief of the McGraw-Hill Engineered Wood Handbook and co-author of the chapter on Wood Construction of the McGraw-Hill Building Design and Construction Handbook.

Mr. Williamson was chair of the ASCE Standards Committee that developed ASCE 16, Standard for Load and Resistance Factor Design of Engineered Wood Construction and is chair of the ANSI Committee that developed PRG 320, Standard for Performance Rated Cross Laminated Timber. He served for 20 years as chairman of the ASTM Committee that developed the standards for glulam. He also served as a peer reviewer for the US Handbook on CLT.

He is a charter member and fellow of the SEI, a past member of the SEI Board of Governors and was the 2010 recipient of the SEI Dennis L. Tewksbury Award.