Adrian Pargeter, Head of Technical and Product Development for Kingspan Insulation details how to reach compliance for fire safety concerning external wall constructions of buildings over 18m high…
There has been some confusion in the industry recently about the use of combustible materials within the external wall constructions of buildings over 18 metres in height. So when industry group BCA issued an updated version of Technical Guidance Note 18 in June this year, the clarification was greatly welcomed. The guidance clearly sets out a number of methods for demonstrating compliance. Building Control Officers have a vital role to play in correctly interpreting these methods, and making sure that the most appropriate approach is adopted to achieve the best all-round performance.
According to the BCA Technical Guidance Note 18: Issue 1 Jun 2015, there are four methods that can provide acceptable routes to compliance:
- Option 1 – The use of materials of limited combustibility;
- Option 2 – Following BR135;
- Option 3 – Submission of a Desktop Study Report;
- Option 4 – taking a holistic Fire Safety Engineering approach.
It is all too easy to jump on the first option as a ‘catch all’ solution. However, taken in the context of the building design, and the complexity of the interactions between the various components, this linear approach to compliance may not automatically deliver the best fire safety solution, and could be detrimental to other aspects of the build, such as thermal performance and overall wall thickness.
BR 135 ‘Fire performance of external thermal insulation for walls of multi–storey buildings’, is directly referred to in each of the Approved Documents B2 for England and Wales (ADB2), and Technical Handbook Sections 2 for Scotland (Domestic and Non Domestic), and sets out the performance criteria for the accepted tests.
The relevant testing for external walls cited by BR 135 is BS 8414 – Fire performance of external cladding systems, Part 1: 2002 (Test methods for non-loadbearing external cladding systems applied to the face of a building) or Part 2: 2005 (Test method for non-loadbearing external cladding systems fixed to and supported by a structural steel frame).
According to the Regulations, and supported by BCA Technical Guidance Note 18, products that have been successfully tested to these standards as part of a complete external cladding system can be deemed to comply for the applications they have been tested in.
Because of the wide variation in possible wall build-ups and material combinations, it is unrealistic to expect every permutation to be tested. The third option, therefore, is to submit a desktop study report from a “suitably qualified fire specialist stating whether, in their opinion, BR135 criteria would be met with the proposed system” (BCA Technical Guidance Note 18). The report should be supported by specifically referenced test data from the products in question.
This option provides a sensible route to determining compliance where precise test data is not available, and could become increasingly prevalent as the number of different façades available on the market continues to expand.
Manufacturers of the differing components comprising a rainscreen system have an important part to play in supporting this work. In what is still an emerging area, expanding testing to cover some of the more common build-ups will help to improve the overall industry knowledge and inform the work of fire safety engineers, also providing an essential part of the information that would be needed to undertake the fourth route to compliance; using fire safety engineering.
Regardless of which route to compliance is being considered, it is always worth checking with the warranty provider for the property in the first instance, as the specified construction may already meet the requirements in many applications.
A holistic fire engineered approach is cited as the fourth option in the latest version of BCA Technical Guidance Note 18. This approach avoids excessive reliance on the standalone performance of products, and instead considers a wide range of issues, such as the building geometry, ignition risk, means of egress and factors restricting fire spread. When applied correctly this should allow better, and more consistent levels of fire safety to be achieved.
A ‘whole building’ fire safety engineering approach will, without question, provide a far better approach in designing buildings with habitable storeys over 18m, through the application of scientific and engineering principles, which require every factor of a building to be fully considered.
Fire Safety for the Future
The role of fire safety engineers will continue to increase over the coming years as modern building design and construction methods require increasingly complex solutions. By understanding and embracing this more holistic approach, planners and BCOs should be able to ensure that effective fire safety is achieved, not only on paper, but also in the final building.
Head of Technical and Product Development
Kingspan Insulation Limited
Tel: +44 (0)1544 388 384