**3. Applicable building codes and standards**

The design basis for most conventionally light-framed single-family dwellings is the International Residential Code (IRC). Manufactured and identified in accordance with ANSI/APA PRG 320 [9], CLT was first recognized in the 2015 IRC [10] as a construction material for walls and floors; however, no prescriptive guidance was provided in the 2015 residential building code or the 2021 version. Construction methods utilizing CLT are regulated by Section R301.1.3 as engineered designs and are based on the locally approved version of the International Building Code (IBC).

The 2015 IBC [11] was the first building code version to incorporate CLT design guidance for the material. Chapters 5 and 6 of the 2015 IBC permitted the use of CLT in wall and floor assemblies within most building construction type categories [12]. For structural design, the 2015 IBC references the 2015 NDS [13]. Chapter 10 was introduced in the 2015 NDS prescribing reference design values for CLT. Additional design guidance was included throughout the standard where applicable. Further

developed guidance was provided in the 2018 versions of both the IBC and the NDS; however, both the 2015 and 2018 versions lacked any guidance on using CLT for diaphragms and shear walls. The 2021 Special Design Provisions for Wind and Seismic (SDPWS) [14] was the first standard to provide engineering design guidance on these topics.
