Rainscreen Fire Barriers for BR 135 and BS 8414 compliance

As rainscreen cladding is becoming much more popular, the interrogation of suitable fire barrier systems has become much more intense. Interfaces with other materials in the wall structure are in the spot light, and the requirement for systems to be BR 135 compliant and in many cases evidence of BS 8414 test series is requested.

BR 135 is prescriptive in terms of the characteristics that rainscreen systems needs to achieve under fire conditions, such as general design and fire spread . BR 135 is the test standard (criteria for fire test). BS 8414 series of tests is a full scale test that is a direct copy of the full rainscreen system either on structural steel frame or on masonry face. BS 8414 is how the test should be performed (test method). BS 8414 is not designed to test individual elements of the rainscreen but tests the full construction as a system. Even the slightest change to one of the elements employed makes the BS 8414 certification void, unless such changes can be proven and formally assessed to be an improvement. Such positive changes can be captured under BS 9414.

It is almost impossible to test to BS 8414 for every combination of materials that form the rainscreen options. Insulation, fixings, fire barriers, support system, external cladding, sheathing board… the number of variances is endless. Using non-combustible materials throughout the system gives rise to BR 135 compliance without the need for testing to BS 8414.

Full Fill Fire barriers should be tested to EN1366-4 and/or BS476 part 20. Open state barriers should be tested to the guidance from TGD19 and the basic principle of EN1363-1. Full Fill and Open State barriers that have been tested to such standards are deemed BR 135 compliant without the need for BS 8414 testing.

Many choices of barrier materials exist but often with limited void size, small ventilation gaps on the open state (often referred to as ventilated rainscreen barrier), or little data to support typical installation and interfaces with other construction elements; details for corners and product abutments can be ambiguous and site presence to review and advise can be frustrating and/or non-existent. Rainscreen fire barriers with a much wider scope and greater technical support include Rockwool SP Fire Stop Slab and SP Fire Stop OSCB products, Tenmat VFB and NVFB and AIM OSCB and Wall Cavity Barrier.

Galaxy Insulation can assist with site visits, toolbox talks, product suitability discussions as part of the services provided in this complex arena. Get in touch with Nigel Gillingham, our Divisional Director for Fire Protection at nigelgillingham@galaxyinsulation.co.uk.

By: Bernadette
Feb 09 2022

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