State-of-the-Art Review of Mass Timber Design Standards and Specifications

Mass timber (MT) is an engineered wood product that has been widely used in Europe and is rapidly gaining popularity in the United States (US). MT structural members consist of multiple wood components connected using adhesives and/or mechanical fasteners. Although wood is a common material in the US, MT is not readily available in the US. Some US structural engineers are reluctant to include MT as a potential construction material in their building designs due to limited MT material availability, cost, and unfamiliarity with MT as a construction material. This unfamiliarity stems from limited US MT education and lack of MT experience at the professional level. This paper attempts to provide a broad-brush MT review for architects and structural engineers interested in incorporating MT in their designs on relevant standards and specifications. Guidelines for designing with MT are provided in the International Code Council’s 2024 International Building Code (2024 IBC) under “Type IV Construction.” The Type IV construction description was initially greatly expanded in the 2021 IBC to allow for tall MT buildings and continues to be included in the 2024 IBC. This paper identifies and reviews the 2024 IBC criteria related to MT. Additionally, discussion is included on military standards pertinent to MT. The composite action of an MT element is highly dependent on the adhesive behavior used to attach the MT member laminations. Consequently, adhesives used with MT members and the testing protocol to validate satisfactory adhesive behavior are discussed.