What class does heavy timber construction fall under?

Heavy timber construction is categorized under Class IV due to its unique characteristics and the materials used in its design. This type of construction utilizes large, solid wood members for structural support, typically with beams and columns that can be at least 8 inches in width.

The classification system for heavy timber is specifically designed to address the fire resistance and structural integrity of buildings. Class IV construction features a high degree of fire resistance, given the larger dimensions of timber, which allows for slower rates of fire spread compared to smaller dimensional lumber. The mass of the timber provides a degree of protection—while it can combust under fire conditions, it will typically burn more predictably and at a slower rate than lighter materials.

This classification emphasizes the fire safety considerations essential for buildings with heavy timber, making it important for fire fighters and safety professionals to understand how these structures behave in the presence of fire. The characteristics of Class IV construction also play a role in planning for fire suppression tactics and emergency response strategies.