Knauf Hybrid Isolator: IC-70-055-6-2x15-SSP-2x15-PP-2x25(229/90)

The Knauf Isolator system is typically used to divide habitable dwellings. The twin stud build up, combined with Knauf’s high performance plasterboards, maximizes acoustic performance in order to comply with building regulations, technical handbooks and guidance for sound insulation.

Testing Methodology: BS EN 1363-1 AND BS 476-20

Knauf interior drywall partition systems* that achieve a fire resistance performance are tested in accordance with BS EN 1363-1 and BS EN 1364-1. These are the up to date and most rigorous test methodology standards to follow.

Determining the maximum height of a drywall partition as per the BS EN 1363-1 fire test methodology, is typically restricted by the 3 metre height of the test furnace.

To understand the true maximum height of the system whilst under fire test conditions (‘Fire State Height’), there are three options. Increases can be determined by utilising greater test furnace heights, via Extended Field of Application (as outlined in BS EN 15254-3 - it is important to note this standard applies to single metal frame symmetrical systems only), or via BS EN 1364-1.

The BS 476-20 standard is also restricted by the 3 metre height of the test furnace. However, under this BS standard, increasing the maximum heights of a system can be based on the ‘Cold State Height’. The cold state height is calculated using structural engineering methods to L/240 @ 200Pascals. (L = Height of wall). Regulatory Requirements

Specific to Approved Document B (England) there is a requirement to use European classifications and fire resistance test methodologies in accordance with BS EN 1363-1 and BS EN 1364-1, which means that the fire state height must be considered. However, Approved Document B (England) currently allows the usage of the BS 476 series, though it should be noted that, following consultation, the full BS 476 series will be removed in 2029. For other nationals, please consult relevant approved documents, technical guidance, and handbooks.

Knauf Approach & Recommendations:

Knauf advise and promote that EN compliance should be followed. That is to say Knauf advise utilising an BS EN 1364-1 fire resistance test and extend the maximum height of a drywall partition system via either BS EN 15254-3, BS EN 1364-1 or via a fire resistance test within a test rig greater than 3m in height.

Projects that wish to use the BS 476 series must gain agreement between the Client, Accountable Persons, Duty Holders, and Local Building Control that the cold state height is an acceptable methodology. For further information on Knauf system types that are applicable to support projects focusing on BS compliance, refer to Knauf Systems Performance Tables (BS compliance).