Even the highest-quality ALC wall panels can lose their full fire protection performance if the panel joints are not properly detailed — this is one of the most overlooked but critical steps to build a fully reliable continuous fire barrier. This guide covers industry best practices to eliminate joint weak points and keep your ALC wall system fully compliant with fire rating certifications.

The first rule for joint detailing is to never leave gaps between ALC panels unfilled. During a fire, even a small 5mm gap can act as a chimney, letting high-temperature flames and smoke pass through to the unexposed side of the wall. All panel joints must be filled with a dedicated fire-resistant sealant that matches or exceeds the fire rating of the ALC panels themselves. For 4-hour fire-rated walls, use a sealant tested to withstand 1200°C+ temperatures without cracking or melting.

For vertical joints between large-format ALC panels, install a thin layer of mineral wool fire stop inside the joint before applying the surface sealant. This adds an extra layer of heat insulation and prevents the sealant from breaking down prematurely under prolonged high heat. For horizontal joints where ALC panels connect to floor slabs or structural beams, use fire-resistant mortar to pack the gap tightly, rather than standard construction mortar that may not meet the required fire performance.

It is also critical to avoid drilling unnecessary large openings through ALC fire walls for pipes, wiring, or ductwork. Any required penetrations must be sealed with certified fire stop collars and fire-resistant putty that match the wall’s full fire rating. Never use ordinary foam or silicone sealant for these penetration points, as these materials will melt and burn away quickly during a fire.

By following these joint detailing best practices, you ensure that the entire ALC wall system performs as a single continuous fire barrier, not just individual panels with weak links between them. This not only passes all fire safety inspections but also delivers the full 4+ hours of fire protection that ALC panels are designed to provide.