Incorrect Junction Between Open-State and Vertical Fire Barriers
The corner junctions between the horizontal open-state cavity barrier and the vertical fire barriers around the window were installed incorrectly and did not follow the manufacturer’s approved design. The barriers were not properly aligned, continuous or sealed at their intersections, leaving gaps through which fire and smoke could potentially bypass the compartmentation.
The junctions must be reconstructed using the specified barrier arrangement, orientation, compression, fixings and corner details contained within the approved and tested system. Manufacturer approval should be obtained for any detail that differs from the standard installation.
- NCQLE reference
- NCQLE-2026-00030
- Quality topic
- Installation quality
- Lesson type
- Failure
- Evidence rating
- Experience
- Published
- 2 August 2026
- Last reviewed
- 2 August 2026
Evidence basis: Supported by relevant professional experience. This learning is provided for professional consideration and does not replace project-specific competent advice, statutory duties or contractual requirements.
Context
The issue was identified during construction of an external façade around a window opening, while the cavity insulation and fire barriers remained exposed and before the outer cladding was installed. Horizontal open-state cavity barriers and vertical fire barriers had been fitted around the window perimeter, but their corner junctions did not correspond with the manufacturer’s approved detail. The inspection provided an opportunity to correct the compartmentation before the façade cavity became concealed. The corner junctions between the horizontal open-state cavity barrier and the vertical fire barriers around the window opening were installed incorrectly. The barrier sections did not meet, overlap or terminate in accordance with the manufacturer’s approved detail, leaving discontinuities and visible gaps at the corners. This interrupted the intended line of compartmentation and created potential routes for fire and smoke to bypass the barriers within the façade cavity.
The transferable lesson
Fire-barrier performance depends on the continuity of the complete system, particularly at corners, changes of direction and junctions between horizontal open-state and vertical barriers. Correct products alone will not provide the required protection if their interfaces are poorly formed or depart from the tested detail. All junctions must be planned, installed and inspected against the manufacturer’s approved design before the façade is closed, with any non-standard arrangement formally assessed and approved.
Recommended action
Prepare coordinated façade fire-barrier drawings showing every corner, termination and junction between open-state and vertical barriers. Review these details with the barrier manufacturer, façade designer and fire specialist before installation begins. Use trained and competent installers, provide an approved benchmark or site mock-up, and install only the specified components, fixings, compression and seals. Introduce a hold-point inspection before insulation or cladding conceals the barriers. Record each junction with location-referenced photographs. Any gap or deviation must be removed and reconstructed to the approved detail, or supported by written manufacturer and fire-design approval before the façade is closed.
Limitations and application
The required junction detail is specific to the tested fire-barrier system, cavity width, substrate, window construction and façade build-up. Open-state barriers intentionally maintain a ventilation gap in normal service, so this designed opening must not be mistaken for an installation defect or filled with unapproved materials. However, the barrier ends, corners and interfaces must still follow the manufacturer’s tested arrangement. A photograph alone cannot confirm the required fire rating or every concealed fixing and overlap. Any remedial detail or departure from the standard installation must be reviewed and approved by the barrier manufacturer, façade designer and competent fire specialist. Materials from different systems must not be combined unless their compatibility and performance are formally demonstrated.