What are the interior structural members of Type IV construction primarily made out of?

In Type IV construction, also referred to as "Heavy Timber" construction, the interior structural members are primarily composed of solid or laminated wood. This method utilizes large, solid wood pieces that are typically heavier and more durable than other types of framing materials. These timber members lend themselves to a distinctive aesthetic while also providing significant structural integrity.

The use of solid or laminated wood in Type IV construction is particularly advantageous because it can effectively resist fire for extended periods, allowing for critical escape times and reducing the potential for structural failure in the event of a fire. Laminated wood, which involves bonding layers of wood together, further enhances the structural integrity and can achieve larger spans without requiring as much vertical support.

In contrast, other options like lightweight metal and reinforced concrete are not characteristic of Type IV construction, as they do not fit the heavy timber framework that defines this construction type. Composite materials can also be utilized in various building contexts, but they are not typically the focus of Type IV construction. Thus, the choice of solid or laminated wood is essential for maintaining the unique properties and safety features of Type IV structures.