Fire resistance in building assemblies is never achieved by a single material alone. While fiber cement boards are widely specified for their A1 non-combustible performance, the fixings used to install them play a critical role in maintaining fire integrity.
In fire-resistant wall and ceiling systems, standard fasteners are often insufficient. Fire-rated assemblies require carefully selected fixings that maintain load-bearing capacity, structural integrity, and compartmentation during fire exposure.
This article explains what changes when fixings must meet fire-resistance requirements, and how to correctly specify fasteners for fiber cement boards in fire-rated assemblies.
Why Fixings Matter in Fire-Rated Assemblies
During a fire, temperatures can exceed 600–1000°C. Under these conditions, fixings are exposed to:
- Rapid thermal expansion
- Loss of tensile strength
- Oxidation and coating failure
- Progressive pull-out or shear failure
If fixings fail prematurely, even non-combustible boards can detach, compromising:
- Fire compartmentation
- Integrity of escape routes
- Structural stability of the assembly
This is why fire-rated performance must be assessed at system level, not material level.
Key Differences Between Standard and Fire-Rated Fixings
Material Composition
Fire-rated fixings are typically manufactured from:
- Carbon steel with verified high-temperature performance
- Stainless steel (A2 or A4 grades) in specific applications
Plastic components, nylon plugs, or hybrid fasteners are not permitted in fire-rated assemblies, even if the board itself is non-combustible.
Coatings and Surface Treatments
Many standard screws rely on coatings for corrosion resistance. In fire conditions:
- Zinc coatings vaporize at relatively low temperatures
- Organic coatings burn away
- Mechanical strength can drop sharply
Fire-rated fixings either use bare steel with verified fire resistance or coatings tested as part of the fire assembly.
Head Design and Load Retention
In fire conditions, head pull-through becomes a major risk. Fire-rated fixings typically feature:
- Larger head diameters
- Reinforced head geometry
- Compatibility with washers where required
This ensures boards remain mechanically restrained even as materials expand.
Fixing Performance During Fire Exposure
Fire-rated fixings must maintain performance in three key areas:
Integrity (E)
The fixing must prevent board detachment that could allow flames or hot gases to pass through the assembly.
Insulation (I)
Failure of fixings can create gaps, reducing thermal insulation and accelerating fire spread.
Loadbearing Stability (R)
In loadbearing or semi-loadbearing systems, fixings must resist deformation long enough to meet fire rating requirements.
Fire-Rated Fixings in Wall and Ceiling Assemblies
Fire-Rated Partitions
In fire-rated partition walls using fiber cement boards:
- Fixings must be metal-to-metal compatible
- Spacing is often reduced compared to non-fire-rated systems
- Edge distances become more critical to prevent cracking under thermal stress
Fire-Resistant Ceilings
Ceilings are exposed to fire from below and subject to gravity load. Fixings must:
- Resist softening and elongation
- Maintain board suspension
- Prevent progressive collapse
This is why fire-rated ceiling systems often specify tested fixing patterns, not just board types.
Service Shafts and Risers
Vertical fire spread is a major risk in shafts. Fire-rated fixings ensure:
- Boards remain in place under prolonged exposure
- Penetrations remain sealed
- Compartmentation between floors is preserved
Timber vs Steel Framing: Fire-Specific Considerations
Steel Framing
- Steel expands rapidly under heat
- Fixings must accommodate differential movement
- Fire-rated self-drilling screws are commonly specified
Timber Framing
- Timber chars but retains core strength
- Fixings must penetrate beyond the char zone
- Screw length and embedment depth become critical
In both cases, fire-rated fixings are selected as part of a tested system, not in isolation.
Spacing, Edge Distance, and Fire Performance
Fire-rated assemblies often require:
- Tighter fixing centers
- Increased edge distances
- Consistent installation tolerances
These measures reduce stress concentrations and prevent early board failure during thermal expansion.
Certification and Testing Requirements
Fire-rated fixings should be supported by:
- EN 13501-2 fire classification reports
- System test evidence (board + fixing + framing)
- Third-party certification where applicable
Fixings that are not explicitly tested or referenced in a fire-rated system should not be assumed compliant.
Common Specification Mistakes
Some of the most frequent errors in fire-rated assemblies include:
- Using standard drywall screws with fiber cement boards
- Assuming non-combustible boards eliminate the need for fire-rated fixings
- Ignoring fixing performance in fire test reports
- Substituting fixings on site without approval
Each of these can invalidate fire certification and expose stakeholders to liability.
Why Fire-Rated Fixings Are a System Decision
Fire performance is never achieved by a single component. Fiber cement boards deliver non-combustibility, but fixings ensure structural continuity under fire exposure.
Correct fixing selection:
- Preserves fire compartmentation
- Maintains system integrity
- Supports regulatory compliance
- Reduces long-term liability risk
Conclusion
In fire-resistant assemblies, the role of fixings is just as important as the boards themselves. Fire-rated fixings for fiber cement boards must be selected based on material behavior under heat, mechanical retention, and tested system performance.
For architects, engineers, and contractors working on fire-critical zones, understanding how fixing requirements change in fire-rated assemblies is essential. Proper specification ensures that fiber cement boards perform as intended — not just on paper, but under real fire conditions.
👉 Visit the Smartfiber Fiber Cement Board page to explore specs, sizes, and delivery options.
Authored by Smartcon Int’l. Trade & Marketing Ltd. on 11.01.2026. All rights reserved.