Encapsulation of Combustibles using EPDM membrane
It was found that the Facade contractor was using EPDM membrane to encapsulate Combustible materials around windows on a HRB over 18M.
No update from Fire engineer and no valid fire engineer report available
Client management Team says its OK
Facade Contractor under pressure from Main Contractor allowing dangerous and unsafe work to continue
- NCQLE reference
- NCQLE-2026-00001
- Quality topic
- Defects and corrective action
- 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
EPDM is not a fireproof wrapper, and it cannot be used to make an otherwise non-compliant combustible material acceptable in a higher-risk building. For external walls of relevant buildings at least 18 metres high in England: Materials forming part of the external wall generally must achieve Class A1 or A2-s1,d0, unless specifically exempted by Regulation 7(3). Membranes are one of those exemptions. However, Approved Document B recommends that external-wall membranes above ground achieve at least Class B-s3,d0. The exemption applies only to the genuine membrane, not to combustible insulation, sheathing, timber, packers, filler materials or other products concealed behind it. Standard EPDM should not automatically be assumed to achieve B-s3,d0. The exact product’s Declaration of Performance, classification report and permitted end-use application must be checked.
The transferable lesson
Covering a combustible material with EPDM does not make it compliant. Every external-wall component must have its own documented route to compliance, verified before the work is closed up. Membrane classifications, underlying materials and installation details should form part of a mandatory inspection hold point, with deviations formally recorded and approved through change control.
Recommended action
At the design and procurement stage, prepare a complete external-wall component schedule identifying each product, its function, manufacturer, reaction-to-fire classification and route to compliance. Where EPDM or another membrane is specified, verify that it is genuinely being used as a membrane, is suitable for the intended application and has appropriate supporting fire-performance evidence. Introduce mandatory inspection hold points before any façade area is covered or closed. Inspectors should confirm that the installed materials match the approved drawings and specifications, record batch and product information, and obtain clear photographic evidence of the underlying construction. Do not accept EPDM as a means of covering or legitimising a combustible material. The underlying component must have its own documented route to compliance or be removed and replaced. Any substitution, unidentified material or departure from the approved external-wall design should be stopped, recorded through a non-conformance report and referred to the Principal Designer and competent fire/façade specialist. Where the project is subject to the higher-risk building regime, the change must also be assessed and managed through the required BSR change-control process before affected work proceeds.
Limitations and application
This lesson applies primarily to external-wall construction on higher-risk and relevant buildings in England. The acceptability of EPDM depends on its intended function, location, product-specific fire classification, supporting test evidence and compatibility with the complete wall system. Membranes may be exempt from the A1/A2-s1,d0 requirement under Regulation 7(3), but Approved Document B recommends a minimum Class B-s3,d0 for external-wall membranes above ground. This exemption does not extend to materials concealed beneath the membrane. Existing buildings, repairs and project-specific details may require separate assessment by a competent fire engineer or façade specialist. This lesson should not replace project-specific design approval, regulatory review or BSR change-control requirements.