Incorrect Install of Intumescent open state fire barrier
A short section of the open-state intumescent cavity barrier appears to have been friction-fitted between a continuation of the barrier, with no visible mechanical fixing. The installation may therefore rely on the plastic carrier to retain the intumescent material. During a fire, the plastic could soften or melt, allowing the unfixed section to become displaced before the intumescent material has fully activated. This could leave a gap in the cavity barrier, compromising the continuity of fire compartmentation and permitting the passage of smoke and flames.
- NCQLE reference
- NCQLE-2026-00008
- Quality topic
- Installation quality
- Lesson type
- Failure
- Evidence rating
- Experience
- Published
- 31 July 2026
- Last reviewed
- 31 July 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
During the installation of a ventilated rainscreen façade, the open-state cavity barrier was inspected before the cavity was closed by the external cladding. The inspection focused on a short section fitted around the metal façade carrier framing, where continuity, retention and compliance with the approved fire-barrier installation detail needed to be confirmed. A short section of the open-state intumescent cavity barrier had been cut and friction-fitted around the metal façade framing. No mechanical fixing was visible securing this section to the supporting construction. The intumescent strip therefore appeared to rely on the surrounding plastic carrier and friction alone to remain in position.
The transferable lesson
Use a larger, continuous section of cavity barrier that spans the interface and can be securely retained with the specified mechanical fixings, such as approved pigtail screws where permitted. Small friction-fitted infill pieces should not be relied upon. All sections must be installed and fixed in accordance with the manufacturer’s tested detail and the approved project design.
Recommended action
Plan barrier lengths and junctions before installation so that small friction-fitted infill pieces are avoided. Use larger continuous sections and secure them with the manufacturer-specified mechanical fixings, including approved pigtail screws where permitted. Inspect all joints, cuts and interfaces before closing the façade, photograph the completed work and rectify any installation that does not match the approved design and tested system.
Limitations and application
The required section size, overlap, fixing type, spacing and supporting substrate will depend on the selected cavity-barrier system and tested fire-performance detail. Pigtail screws or alternative fixings must only be used where permitted by the manufacturer and approved design. A visual inspection may not confirm concealed fixings, so installation records and photographic evidence should also be reviewed.