Mass timber has moved from a niche sustainability pitch to a genuine structural option on projects across the Gulf, but SBC 201 was written before this material had a clear home in Saudi construction practice. Teams proposing cross-laminated timber or glulam structures now need to understand exactly how the code treats combustible mass structural elements before committing to a design.

Why Mass Timber Complicates a Prescriptive Code

SBC 201 classifies construction into defined types based largely on combustibility and fire-resistance rating, closely following the structure of the International Building Code. Traditional construction types split cleanly into noncombustible, such as steel and concrete, and combustible, such as light-frame timber. Mass timber does not fit either category comfortably, since large-section engineered wood panels behave very differently in a fire than thin timber framing.

The 2021 edition of the International Building Code, which the current SBC 201 aligns closely with, addressed this by introducing three new construction types specifically for mass timber, distinguishing between exposed and fully protected timber elements based on the degree of fire protection applied.

How Mass Timber Actually Performs in Fire

The behaviour that makes mass timber code-compliant is charring. When exposed to fire, the outer layer of a cross-laminated timber or glulam member chars and forms an insulating layer that slows heat penetration into the remaining wood, allowing structural capacity to be calculated based on the reduced, uncharred cross-section.

●        Large-scale compartment fire testing has demonstrated mass timber elements can maintain structural performance through several hours of fire exposure when properly sized

●        Char rate calculations, similar in principle to methods used in international timber design standards, allow engineers to size members so the fire-resistance rating is achieved through material thickness rather than applied fireproofing alone

●        Connections between timber members remain one of the more technically demanding details, since exposed steel connectors can draw heat into the timber and compromise the char layer's protective effect

Concealed spaces are largely eliminated in solid mass timber construction, which removes one common avenue for fire spread found in conventional light-frame buildings, though service penetrations still need proper firestopping regardless of structural material.

Applying This Within the Current Code

Because the code does not yet contain fully developed prescriptive tables specific to every mass timber configuration, most mass timber projects in the Kingdom currently rely on a combination of tested assemblies from international suppliers, calculation methods referenced through their alignment with international standards, and, in some cases, a performance-based justification reviewed directly with the authority having jurisdiction.

This makes early engagement with a fire engineer essential. A design team that finalises architectural intent for exposed mass timber before confirming which compliance path the local authority will accept risks a costly redesign later, particularly around connection detailing and any exposed timber surface area limits.

What This Means for Project Planning

Teams considering mass timber should budget time for a fire engineering review well before structural design is finalised, not after. Confirming fire-resistance rating requirements, exposed surface limitations, and connection protection strategy early avoids the common trap of an architecturally committed design that later needs significant rework to satisfy SBC 201 requirements.

Suppliers can usually provide fire test data for standard panel configurations, but project-specific connections and unusual exposure conditions typically still need independent verification against the applicable fire-resistance rating.

Planning Mass Timber Projects With Confidence

SBC 201 continues to evolve alongside the international codes it references, and mass timber construction sits at exactly the kind of intersection between new materials and established prescriptive frameworks that benefits from early, specific technical review. Getting fire engineering input at the concept stage, rather than treating it as a late-stage compliance check, is the most reliable way to keep an ambitious mass timber design on schedule.

If your project team is weighing a mass timber structural system, it is worth confirming the applicable fire-resistance and compliance path with a qualified consultant before the structural concept is locked in.

FAQs

1. Does SBC 201 currently have specific provisions for mass timber?

It is not yet equipped with the complete prescriptive tables for all possible mass timber assemblies; hence, projects have to rely on international test data, calculations, or performance-based evaluation.

2. Can mass timber be left exposed in a building under SBC 201?

This will depend on the type of construction and the fire resistance requirements pertinent to the project, which may require a compliance approach to be agreed upon with the authority.

3. Why are connections a particular concern in mass timber fire design?

The steel connections, being exposed to heat, could act as conduits of heat and affect the protective layer of char that imparts fire resistance to the member.

4. How is the fire resistance of mass timber calculated?

Through calculations of char rate, which factor in the reduced cross-sectional area after charring, following international design principles for timber members.

5. When should a fire engineer be involved in a mass timber project?

Even at the concept design level, the approach adopted determines architectural exposures, connection details, and the project schedule as a whole.