Around the world, dangers associated with flammable cladding on high-rise buildings have been demonstrated through the Grenfell fire in London and through many other building fires.
In many cases, problems have centred on aluminium composite panels which contain a flammable polyethylene core. Problems have also been found with use of expanded polystyrene.
In response, regulators have acted.
In the UK, metal composite panels with an unmodified polyethylene core can no longer be used on any building of any height.
In the UAE, use of aluminium composite panel cladding was prohibited when the country’s Fire and Safet Safety Code of Practice was updated in 2016 (the code was made public in 2017).
In Australia, that raises questions about which facade materials are safe and compliant with the National Construction Code (NCC).
Such issues were discussed during a recent webinar that was hosted by Engineers Australia and sponsored by building products manufacturer Brickworks. Speakers included Doron Levy, Proprietor and General Manager at international fire engineering consultancy Fahrenheit Global, and Cathy Inglis AM, a director of Housing Industry Association and General Manager – Technical & Innovation at Brickworks.
At the outset, it should be acknowledged that some products are now banned entirely and cannot be used.
In Victoria, both flammable ACP and expanded polystyrene have been banned for use on all buildings with two or more storeys – although ACP can be used if the core is made up of less than 8 percent flammable material.
In New South Wales, aluminium composite panels with greater than 30 percent polyethylene by mass in their core have been banned since 2017. Whilst this represents a level of allowance which is greater compared with that provided for in Victoria, Levy cautions that an 8 percent rule similar to that in Victoria may become a requirement in the future and may be expected by financiers and insurers.
Indeed, as part of the state’s program to remediate existing buildings, the NSW Cladding Product Safety Panel recommended that that any ACP with a core of greater than 8 percent flammable material should be removed and that there be no endorsement for remediation by either alternative solutions or fire breaks. The panel also recommended that cladding should be mechanically fixed as large pieces of panelling which have been fixed by either glue or double-sided tape may fall off a building and become debris in a fire.
Next, Inglis points out that cladding and façade selection should incorporate a range of considerations in addition to non-combustibility. These include appearance, structural stability, serviceability, waterproofing and condensation, thermal and solar transmission, acoustics, sustainability and durability.
Nor do problems with facades stop at combustible cladding.
When removing combustible cladding as part of Project Remediate in NSW, a litany of problems relating to facades have been uncovered. These include use of incorrect materials for supporting attachments to the structure, corrosion in fixing materials and railing that supports the cladding along with issues relating to waterproofing and condensation.
What the NCC requires
So what does the National Construction Code require?
The following is outline (based on the presentation from Inglis), describes the situation under the 2022 update of the Code. This is scheduled to be adopted by states and territories on 1 May 2023.
In respect of commercial, public and multi-residential buildings (Class 2 to 9 buildings), NCC provisions relating to fire safety are set out in Section C of Volume One of the code.
Under these provisions, functional statements C1F1 and C1F2 in NCC 2022 state that buildings need to:
- Be constructed to maintain structural stability during a fire to allow occupants to escape, to enable fire brigade intervention and to avoid damage to property
- Have safeguards to prevent fire spread to exits, to sole occupancy units, between buildings and within a building.
Following on from this, performance requirements (C1P1 and C1P2) require buildings to have elements which will:
- Maintain the structural stability of the building during a fire; and
- Avoid the spread for fire to exits, to sole occupancy units, to public corridors, between buildings and within a building.
To meet these requirements, engineers can use either a performance solution, a deemed-to-satisfy solution (DTS solution) or a combination of both.
Speaking particularly of the requirement to resist the spread for fire, Inglis says options available using a DTS solution include:
- Using a material such as bricks, concrete, glass or steel which is known and deemed to be non-combustible (see below)
- Using a product that has been tested for non-combustibility to Australian Standard AS1530.1
- Using a product which is deemed to be non-combustible according to products which have low or limited combustibility.
Meanwhile, options to meet the requirements using a performance solution include:
- Demonstration of compliance through verification method CV3, which includes the new AS 5113 façade assembly testing standard and additional fire safety measures.
- Developing a custom performance solution for the specific project and system to be used.
Under the deemed to satisfy provision C2D10, requirements for buildings depend on their building type: Type A, Type B and Type C.
As far as external walls are concerned (the focus of this article), DTS provision C2D10 requires these to have non-combustible building elements and components incorporated in them (including the façade covering, framing and insulation) if they are either a Type A or Type B building. This includes hotels, multi-residential apartment complexes and public buildings which are two or more storeys in height and office, retail or industrial buildings which are three or more storeys in height.
In regard to the DTS provisions, several changes have been made in NCC 2022.
- An expansion of the list of ancillary items which are exempt from the requirement to be non-combustible. Previously, the list included only gasket, calking, sealants, termite management systems and glass and along with damp-proof courses. In NCC 2022, items such as thermal breaks, compressible fillers, waterproofing materials, paints, adhesives, packers and more have been added. These new items no longer need to be non-combustible.
- A new list of materials which are considered to be non-combustible and can be used whenever a non-combustible material is required. This includes concrete, steel, masonry (including mortar), aluminium (including alloys) autoclaved aerated concrete (including mortar), terracotta, porcelain, ceramic, natural stone and more. Whilst these are well-known to be non-combustible, the previous absence of a specific listing meant that people were asking for testing of bricks, concrete or terracotta tiles despite the known non-combustibility of these material.
As with previous NCC versions, the DTS provisions in NCC 2022 continue to specify a range of materials which have low combustibility and can be used where a non-combustible material is needed.
These include plasterboard, fibre cement sheeting, bonded laminates (under certain conditions) and other materials.
For bonded laminates to be used, NCC 2022 includes a new requirement that these be fixed in accordance with Specification C2D15, which requires mechanical fixing to the external façade and does not allow for adhesive fixing.
Small or Large-Scale Tests?
As mentioned above, one option to demonstrate compliance using the DTS solution is to use a product that has been tested for non-combustibility to Australian Standard AS1530.1.
To do this, Inglis says there are two common tests.
The first is a small-scale test which is performed in accordance with Australian Standard AS 1530.1.
Under this test, a small sample of the material is placed inside a furnace and subjected to temperatures of 750 degrees Celsius. The material is considered to be non-combustible if there is no development of flame or excessive heat when the sample is immersed at this temperature.
It is important to note that materials can pass this test and yet still have some combustible components. Here, Inglis gives the example of a sample of extruded polystyrene (a lightweight aggregate), which is protected by the cement matrix of the product.
Whilst being straightforward, Inglis says this test has limitations when it comes to multi-layered products and multi-compositional products.
Beyond that, a larger scale test is that carried out under Australian Standard AS 5113. The test was introduced in NCA Amendment 1 2016 as a means to demonstrate non-combustibility.
Use of this test is necessary if you are using Verification Method C1V3 to demonstrate compliance with the performance requirement through a performance solution.
Furthermore, the test is considered to be more comprehensive compared with the AS 1530.1 test referred to above. It is therefore preferred for testing of more complex wall systems which are multi-dimensional or multi-layered in nature.
To be used under the verification method, the material must achieve a classification of EW (external wall) under this test.
The test involves a complete wall which is almost ten meters high. A series of thermocouples are placed throughout the wall to measure temperature not only through various heights but also though the depth of the wall. This measures the temperature not only through the external face but also through the insulation, framing and internal lining of the wall.
The wall is positioned over a crib of timber which is set alight as a fire source. Once the fire is lit, the test continues until the timber crib falls over and the fire burns out. To test how the fire will behave where the walls intersect, a wing wall is included in the test.
To pass, the wall system must satisfy nine criteria. These include maximum temperatures at certain times after ignition, no flaming, no opening of the cladding or spreading beyond the specimen, no flaming debris within a certain timeframe and limited debris mass of 2 kilograms.
Note that if using this test for the verification method, the wall system which is tested must be constructed exactly as the system which is proposed for use on their project.
Note also that if the wall system used in the test contained a cavity and incorporates cavity barriers, these must be used in the actual construction. Should you wish to vary any part of the wall system used, a further test will be required to obtain the EW rating for that specific wall system.
If using this test to demonstrate compliance under the aforementioned verification method, the NCC has several other requirements including additional sprinklers.
ACP Fails – So do some other materials
So how do various products measure up?
- Not surprisingly, the highly combustible aluminium composite panels with a polyethylene core are a complete failure. Five minutes into the large-scale test, the flames had risen and the aluminium had shrunk and melted away. Ten minutes in, the test was stopped and immense damage had been done to the wall.
- An interesting result came from test of 9ml fibre cement boards. These are actually allowed to be used as they have an exemption under the limited combustibility list referred to above. As a personal opinion, Inglis advises against use of these products for external cladding in cases as they fail both the 1530.1 test and the AS 5113 test. When the test was stopped after fourteen minutes, significant damage was evident to the fibre cement boards. During the test, the fire came up through the frame, insulation and plasterboard lining which is the inner surface of the wall façade.
- By comparison, a brick wall passed the AS5113 test. The material showed some smoke and staining but was basically intact.
In addition to the above, NCC 2022 also includes a new fire safety verification method under which compliance with the performance requirements is verified when a building is designed in accordance with the fire safety verification method standard, a performance based design brief, a fire strategy, stakeholder involvement and the required level of safety.
Compared with other means of demonstrating compliance with the performance requirements, Inglis says this is relatively onerous. Nevertheless, it may be an option for custom façade for which compliance cannot be demonstrated through any other means.
What are good options?
Finally, aforementioned speakers talked about potential options which may be considered.
According to Inglis, these include:
- Ceramic and terracotta facades on aluminium or steel hanging systems. These have been newly listed as non-combustible but also provide durability, involve little maintenance and retain their colour over a long period (the Brickworks Terracade system has a 100-year warranty on the tiles for colour-fastness and durability).
- Tiles or bricks on metal hanging systems. These have the ability to be prefabricated, which in turn provides for greater control over the layering and build-up of the material to more easily meet thermal and condensation requirements.
- Thin brick on railing systems. These have been around for awhile. Brickworks will be launching a system later this year.
Meanwhile, Levy says innovative materials are making their way to Australia and provide alternatives to combustible materials.
These include ceramics/terracotta, natural slate, anodised aluminium and non-combustible render.
He says these offer numerous qualities in addition to being non-combustible.
The ceramic products are made through a range of processes which deliver a strong and sturdy material.
Meanwhile, the natural stone facades such as natural slate come in shades ranging from dark grey to black and can add sobriety and sophistication to the appearance of any façade.
The material also offers excellent thermal performance, is waterproof, is easy to install and has a lower environmental impact as a result of being made from a natural material.
Meanwhile, each piece is made by hand without chemical addition or treatment.
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