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Heavy Timber & Fire Resistance: A Closer Look at Safety & Strength

Heavy Timber & Fire Resistance: A Closer Look at Safety & Strength

Embracing timber as a primary construction material brings forth a multitude of benefits that extend far beyond aesthetic appeal. The innate qualities of timber, marked by its versatility, sustainability, and weight-to-strength ratio, have positioned it as a favorable choice in contemporary construction. However, heavy timber stands out not only for these impressive features but also for a remarkable and perhaps surprising quality — fire resistance. As we delve into the science behind heavy timber’s fire-resistant properties, we’ll also shed light on additional measures that can enhance and complement its fire resistance.

Charring Process

Heavy timber’s distinct fire-resistant attribute is its capability to char in a controlled manner when faced with flames, rather than burning through and combusting. As observed and documented over years of research and testing, heavy timber’s behavior in a fire is predictable. When heavy timber is exposed to fire, its outer layer undergoes a charring process, creating a protective barrier. Understanding this charring process is crucial in designing and assessing the fire performance of heavy timber structures.

Insulating Properties

As the outer layer of heavy timber chars, it insulates the inner, unburned wood from the flames. This insulation significantly slows down the progression of the fire, prevents the fire from penetrating deeply into the timber, and provides a crucial advantage in terms of safety and structural integrity.

Predictable Behavior

Unlike some materials that may behave unpredictably under intense heat, heavy timber’s response to fire is well understood. This predictability allows for effective design and engineering, facilitating the incorporation of safety measures that meet stringent building codes and regulations. The National Fire Protection Association (NFPA) and the International Building Code (IBC) provide prescriptive information for heavy timber fire safety within their standards. Recently, the IBC released many revisions and updates to mass timber building height allowances and associated fire safety requirements. Learn more about timber building codes and fire safety regulations in our previous blog post.

Comparative Advantage

The reliability of heavy timber in fire scenarios enhances its appeal as a construction material in various applications. Traditional construction materials like concrete and steel do not possess inherent fire-resistant properties. While concrete may offer better fire resistance than steel, both materials conduct heat more rapidly and can undergo significant strength loss and structural compromise when exposed to high temperatures. Thus, while concrete and steel have their merits in construction, heavy timber’s unique characteristics make it a compelling choice in builds where fire resistance is a critical consideration.

Additional Measures

In addition to the inherent fire resistance of heavy timber, a strategic combination of design, technology, and preventative safety measures further fortifies its protection against fire hazards. Applying fire-resistant coatings to slow the speed of charring, installing automatic sprinkler systems for rapid fire suppression, and implementing fire barriers and compartmentation to contain fires are just a few design and technology examples. Regarding preventative and proactive measures, performing environmental assessments, installing early warning systems, doing emergency egress planning, conducting regular inspections, and coordinating with emergency services contribute to an intentional and comprehensive approach to fire safety within heavy timber structures.


When faced with fire, heavy timber’s unique charring process, insulating properties, and predictable behavior positions it as a reliable choice in construction. The comparative advantage it holds, coupled with additional safety measures available, solidifies heavy timber’s place as not just a building material but a safeguard against unforeseen challenges.

At Mid-Atlantic Timberframes, we’re advancing the art of timber construction, and we’re here to offer our knowledge in addressing any fire safety or building code and regulation questions that you might have. Contact us today to speak with our experts and learn more.


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