Title 24 Explained: California’s Code for Fire-Safe Decking and Siding

California’s wildland-urban interface (WUI) zones present unique challenges when it comes to building materials and fire safety. To address these risks, the state established Title 24 of the California Code of Regulations; a comprehensive set of standards designed to improve building performance and fire resilience. Within Title 24, Section 12-7A-4.8 outlines the requirements for exterior decking and siding in high-risk fire areas.

California Building Standards Code and the Role of Title 24

Title 24 is the official California Building Standards Code. Part 12 of this code focuses on fire-resistance in construction, particularly for structures located in WUI zones where wildfires and windborne embers pose serious threats. Enforced by the California State Fire Marshal (CSFM), Title 24 helps protect communities prone to wildfire exposure, ensuring materials used on the exterior of homes and buildings reduce ignition risks.

Section 12-7A-4.8 specifically applies to decking and similar horizontal surfaces. It connects directly to Chapter 7A of the California Building Code, which provides the broader context for fire-resistant construction in wildland areas. The goal is simple but critical: minimize the vulnerability of structures to ignition from radiant heat and embers during a wildfire event.

Testing Criteria for Compliance

Decking materials approved for use under Title 24 must meet strict testing requirements. The CSFM mandates a series of performance-based tests:

• ASTM E84: Measures Surface Burning Characteristics and requires a Class A Flame Spread Index (FSI) of 25 or less. Both MOSO^® Bamboo Thermo and N-durance products achieve an FSI of 10, offering exceptional fire resistance well within the Class A rating.
• ASTM D2898: Typically used to evaluate how fire retardant treated (FRT) lumber performs after weathering. This standard does not apply to MOSO^® Bamboo, as its fire resistance is inherent to the material’s density—not the result of a topical treatment or coating.
• SFM Standard 12-7A-4: A combined evaluation of fire performance under simulated wildland fire conditions.

Only materials that pass these rigorous tests, without relying on chemical fire retardants or plastic fillers, are added to the CSFM WUI-approved product list.

How MOSO^® Bamboo Meets Title 24 Standards

MOSO^® Bamboo Outdoor products meet and exceed California’s fire safety requirements. Both products have achieved a Class A rating under ASTM E84 testing with a Flame Spread Index (FSI) of 10. This performance holds even after UV and moisture conditioning per ASTM D2898 protocols—demonstrating long-term reliability. Importantly, MOSO^® passed the CSFM 12-7A-4 test protocols, ensuring compliance with California’s Wildland-Urban Interface (WUI) fire safety standards.

Unlike fire-retardant treated (FRT) lumber, which may lose effectiveness as its chemical treatments degrade, MOSO’s fire resistance is inherent to its density. It is not the result of surface coatings or additives, meaning its performance doesn’t diminish over time. Additionally, MOSO^® decking complies with major international standards including CAN/ULC for Canadian projects and rooftop-specific certifications like ASTM E108 and CAN-ULC S107. With its durability, Class A fire rating, and proven resistance to decay and termites, MOSO^® Bamboo remains a resilient, natural solution for high-risk building zones.

Benefits of Using Title 24-Compliant Materials

Using decking materials that meet Title 24 requirements provides a range of benefits:

• Code Compliance: Ensures your project passes local inspections and meets current fire safety regulations.
• Improved Safety: Reduces the risk of ignition and property loss during wildfires.
• Market Advantage: Enhances the appeal of a home or building for buyers and developers seeking resilient, sustainable construction.
• Long-Term Performance: Certified materials are built to last in extreme conditions, reducing maintenance and replacement costs.
• Insurance Compatibility: Meets many new insurance requirements in fire prone states.

Frequently Asked Questions

What is the difference between WUI and Title 24?
The Wildland-Urban Interface (WUI) refers to geographic zones where homes and buildings are located near or among wildland vegetation—areas at high risk of wildfire. Title 24, meanwhile, is the regulatory framework in California that sets specific construction and fire safety requirements for buildings, particularly within these WUI zones. It dictates what materials and building practices are acceptable to reduce fire risk.

Is Title 24 required statewide or only in specific counties?
Title 24 is a statewide building code. However, its enforcement is more rigorous in designated fire-prone areas, especially those identified as WUI zones. Local jurisdictions may apply stricter rules depending on wildfire history and risk assessments.

How do I verify if a product is Title 24 compliant?
To determine compliance, consult the California State Fire Marshal’s WUI Building Materials Listing Program. This database includes decking, siding, and other materials that have passed required tests. Manufacturers also often provide compliance documentation that references the CSFM listing.

Does compliance require third-party certification?
Yes. Products must undergo third-party laboratory testing to meet standards such as ASTM E84 and SFM 12-7A-4. Only after passing these tests and review by the CSFM can products be officially listed. This process ensures that materials used in fire-prone zones maintain reliable, consistent fire resistance.

Build Safer with MOSO^® Bamboo

As wildfire risks continue to rise, California’s Title 24 regulations help protect homes and communities by setting standards that limit fire hazards and promote safer building materials. Choosing materials like MOSO^® Bamboo that meet these high standards, without relying on synthetic or chemical treatments, helps builders and homeowners create safer, more sustainable spaces.

View our full fire safety certification documentation, connect with a local MOSO^® dealer, or request a sample today.

Fire resistance is Inherent not applied.