Whilst we can’t always prevent a fire from occurring, we can take steps to avoid or reduce the likelihood of harm coming to the people within or in the vicinity of the building. The fire performance of cladding systems is assessed and recorded using a plethora of tests, guidance documents, and classifications. This can make it challenging to understand how they relate to one another and, importantly, whether or not a product is suitable for a particular application.
In the next couple of blogs, we’ll explore some of the different tests and classifications, including what they currently involve.
Insurer or Building Regulations
Whilst there are a number of fire tests and classifications available, these typically focus on one of two main concerns: whether materials meet Building Regulations (such as BS 8414) or insurer-approved standards (such as FM 4880 and LPS 1181).
Building Regulation classifications are focused on maintaining life and providing time for individuals to leave safely.
Insurer classifications are focused on asset protection, which aims to prevent or reduce the likelihood of damage to, or loss of, a building.
In this blog, we will briefly explain the tests currently used to support Building Regulation requirements.
Approved Document B to the Building Regulations in England and Wales (ADB), and the Scottish Technical Handbook Section 2 – Fire are the three approved guidance documents that give set criteria for meeting acceptable standards of fire safety and performance in buildings. Each document has a version for domestic and non-domestic properties, with more stringent criteria for buildings with habitable storeys above 18 metres.
Requirements above 18 metres
Under the guidance in ADB in England and Wales and the Scottish Technical Handbook, different paths are provided for cladding panels to achieve compliance with fire safety requirements:
Linear Route to Compliance
Under the linear route, a cladding construction can be deemed compliant with fire safety requirements if all elements are classified to be of limited combustibility in England and Wales or non-combustible in Scotland based on specific small-scale fire testing.
Whilst this may appear to offer a simple route to compliance, there are significant issues with relying solely on small scale testing. As these tests only look at the performance of individual products (or small product samples), it’s difficult to determine how they would interact with other building elements when installed as part of a specified build-up and exposed to a real-life fire situation. This ‘linear route to compliance’ also doesn’t take into consideration factors such as building height, use, boundary, and the overall performance required for façade build-ups. To gain a more accurate understanding of how a particular façade system will perform in an actual fire, large-scale testing is required. This can be achieved via the direct performance route to compliance.
Direct performance route
The direct performance route is conducted under the design methodologies within BR135 – Fire Performance of External Thermal Insulation for Walls of Multi-storey Buildings. This guidance document lays out the criteria for the large-scale testing of cladding systems using BS 8414 – Fire performance of external cladding systems. There are two different test methods, designed for non-loadbearing cladding systems either applied to a masonry face or fixed to and supported by a structural steel frame. According to ADB and the Technical Handbooks, products which are successfully tested as part of complete cladding systems are deemed compliant in the specific configuration in which they were tested.
BS 8414 is designed to mimic a high-rise building, measuring fire spread and flame propagation. It replicates a fire starting inside a room, breaking out through a window and exposing the external façade to fire.
The cladding system is fitted to a test rig in two wings, forming an internal corner. It is constructed to a minimum height of 8 metres – complete with joints, seals, fire breaks, and penetrations as in the final building.
The rig is exposed to flame for 30 minutes from a 2m x 2m wooden crib ignition source placed at ground floor level. It is then monitored for up to 30 minutes following the removal of the flame source.
During the test, temperature is measured and maximum temperatures are specified which cannot be exceeded to achieve a pass. The test also measures fire spread in so far as if fire spreads past the perimeter of the test rig, it is deemed to have failed.
Desktop Study Report
An additional compliance pathway based on the performance route is also offered in England and Wales under BCA Technical Guidance Note 18, Issue 1 (June 2015), which states that “If no actual fire test data exists for a particular system, the client may instead submit a desktop study report from a suitably qualified fire specialist stating whether, in their opinion, BR 135 criteria would be met with the proposed system”.
The guidance advises that test data from an independent UKAS accredited testing body should be used to support the report, with reference to any actual tests performed on the product(s) being used. The qualified fire expert will typically require more information on construction and engineering details, including building plans, elevations, and fire barriers.
Fire Safety Engineering route
Under this approach, a fire safety engineer assesses every element of a building’s construction to determine its fire performance. This includes construction materials, structures, active and passive fire protection measures, and building orientation. To ensure the engineers can make well-informed decisions, working with the most accurate data, such as large-scale test data (eg. BS 8414), is recommended.
You can read more about fire tests and research via our Fire Performance pages.
Recent events have highlighted many inadequacies in the Building Regulation requirements as they currently stand, and in how they are interpreted. EPIC is involved in the consultation process to review Approved Document B, and will be covering some of the issues in future blogs.
In the next blog, we will look at FM approval and LPS 1181.