**2. CLT as a building construction material**

The basic desirable sustainable attribute of lumber as a construction material is that it sequesters much carbon dioxide during its growth process while releasing oxygen back into the air, which signifies the favorable carbon impact that wood has on the environment. While up until a couple of decades ago, the use of lumber in construction was limited to light-frame systems due to section size limitation dimension lumber, the use of lamination technology has opened new possibilities.

According to the CLT Handbook [2], CLT is defined as a prefabricated solid engineered wood product made of at least three orthogonally bonded layers of solidsawn lumber or structural composite lumber (SCL) that are laminated by gluing of longitudinal and transverse layers with structural adhesives to form a solid rectangular-shaped, straight, and plane timber intended for roof, floor, or wall applications (**Figure 1**).

CLT is manufactured and identified according to ANSI/APA PRG 320 (APA 2020). In addition to the testing and manufacturing requirements discussed, this standard also defines the terminology, symbology, grades, and reference design values, which are used throughout the industry. The reference design values in this publication can be used for preliminary design if no other information is available; however, manufacturers are required by the standard to publish their own panel specific data. There are currently several manufacturers that service projects located in the United States. The Engineered Wood Association (APA) lists the major manufacturers along with their product testing reports online [5]. Most of the manufacturers listed are located in the western regions of the United States and Canada; However, Nordic and International Beams (IB) have facilities in Quebec and Alabama, respectively. In addition to the manufacturer directory, the APA provides many free downloads for CLT case studies and informational guides.

*Structural Design of a Single-Family Residential Dwelling Using Cross-Laminated… DOI: http://dx.doi.org/10.5772/intechopen.110790*

#### **Figure 1.** *Isometric view of a three-layer piece of CLT construction material (Wikimedia commons contributors 2021) [4].*

As a building construction material, CLT is primarily used to prefabricate twodimensional (2D) load carrying panels that are used as components in floor, roof and wall assemblies [2]. CLT panels are not typically designed to be exposed to moisture and are not intended to be utilized as cladding panels [2], therefore they require protection by the building envelope system to prevent deterioration. With proper design, CLT can be used in Type III, IV and V construction as classified by the IBC [6]. Examples provided in the 2021 Mass Timber Design manual [7] show CLT used as an alternative to masonry walls in multi-story residential or office buildings. Both the U. S. edition [2] and the Swedish edition [8] also show examples of CLT being utilized for the construction of single-family dwellings.
