Aluminium Decking Explained
Recent changes to the building regulations Part B (Fire Safety)
There are three approaches permissible to meet Part B of the Building Regulations:
- Approved Document B suitable for single dwellings and simple construction
- Advanced Approach whereby BS 9999: 2017 is used and provides a more technical structure, allowing risk-based principles to be applied to the design
- Fire Safety Engineering. Fire Safety Engineering can in some cases be the only way of achieving an acceptable standard of fire safety in certain types of buildings which are too large or complex to be covered by other means (e.g Buildings over 50metres). BS7974:2009 provides the principal Code of Practice for the application of Fire Safety Engineering and includes the requirement for a Qualitative Design Review.
Prior to the tragic events of Grenfell Tower fire in 2017, the Approved Document B referred to testing in accordance with BS476 and classification of national classes (Class 1, Class 0 etc). For example, the definition of materials of limited combustibility included testing to BS476-11:1982 and BS476-4:1970. Also buildings over 18m in height (unless they were close to a boundary) were permitted to use materials which were Euroclass C (in accordance with EN 13501-1) or national class 1 or better. Above 18m in height the materials had to be national “class 0” or class B-s3,d2 (in accordance with EN 13501-1 or better.
An alternative method was allowed where the material shall be tested to BS8414-1:2002 or BS8414-2:2005 and the results meet the requirements of BR135.
BS9999:2017 included (and still does) very similar guidance, including virtually the same diagrams.
Approved Document B has been updated in 2018, 2019 and in 2020. Among the relevant changes made to the approved document include that distinction is made regarding residential buildings over 18m (“relevant buildings”) and more particularly that the reaction to fire criteria for these has been made more strict, the criteria is now A2-s1,d0 (when tested in accordance with EN 13501-1) or better. The national classes have been removed from ADB, and the BS8414 tests have been updated.
Furthermore, the most prescriptive and significant change is the change regarding Regulation 7. Whereas Part B of the building regulations has not changed (the Approved Document has), Regulation 7 has significantly changed and a very unusual step has been made to include prescriptive requirements within the regulation, to the effect that any materials in the external wall shall be A2-s1,d0 or better when tested in accordance with EN13501-1:2009. This is a significant change in substance and style of regulation.
BS9999:2017 has not been updated to reflect these changes, and is widely recognised as being overdue for an update.
Note that the functional requirement of Part B of the building regulations hasn’t changed.
The MHCLG (now called the Department for Levelling up, Housing and Communities) has applied an un-precented approach in the change to the regulations and guidance because they have been given reason to believe that the industry cannot be trusted to make professional judgements on its own, via the updates to Regulation 7 and the publishing of its Advices Notes
22nr Advice Notes were published throughout 2018 and 2019. Some of these gave specific recommendations about the investigation and removal of combustible materials.
In December 2019, this gave rise to the EWS1 form. The EWS1 form was intended to put some structure to how buildings could be assessed in a consistent manner to avoid various interpretations of the MHCLG guidance notes. The EWS1 form uses two options, which are split into two sub categories:
OPTION A, intended where it is relatively obvious what the cladding or external walling and the attachments (balconies etc) would contribute to fire (by virtue of the materials used and the fire stopping systems at compartment lines and around windows), and this can be completed by a competent person who doesn’t need to be a fire engineer but meets some professional competence requirements. Resulting in one of the following classifications:
A1 – This is considered the lowest risk of fire spread.
A2 – Where there are only minimal amounts of materials not meeting the combustibility criteria and so no work is needed to replace materials.
A3 – Where A1 or A2 doesn’t apply for example, the façade may be non-combustible but flammable decking needs to be replaced with non-combustible decking such as aluminium decking or mineral composite.
OPTION B, where there are flammable materials but a highly competent specialist (usually a Fire Engineer) has assessed the materials and made a judgement about what works are necessary.
B1 – There are flammable materials in the façade, but the Engineer has deemed that the risk is acceptable, and no works are necessary.
B2 – There are flammable materials in the façade (or there are materials which cannot be identified) and works are necessary to reduce the risk of fire spread.
The twenty two Advice Notes were withdrawn by MHCLG and replaced with the Consolidated Advice Note published on 20th January 2020.
This has since been withdrawn on 10th January 2022 and regarding risk assessment of external walls has been replaced by PAS9980, then later this year mor guidance was published on smoke control systems with the changes being brought about by BS 9991 and the new regulations in relation to fire doors has been clarified in the Fire Safety (England) Regulations 2022.
What does A1 or A2 fire rating mean?
Confusingly, EWS1 has classifications A1, A2 etc, but these mean completely different things, refer to the EWS1 form for more details on this. But when we are talking about the combustibility (reaction to fire) of materials such as aluminium decking, the A1 and A2 ratings are from EN13501-1, there are called Euroclass ratings. The classification for each section is determined by the outcome of a series of tests. The Euroclass system comes from BS EN 13501 (Reaction to fire). Primarily we are interested in BS EN 13501-1 Classification using data from reaction to fire tests.
EN13501-1 provides classifications for combustibility from A1 through A2 to B,C,D,E and F. Where A1 is the best (non-combustible) and F is the worst (most combustible). In the classifications A2 through to F, there are added components to the classification for smoke and flaming droplets. S1 is the lowest amount of smoke whereas S3 is the highest amount of smoke. Likewise, d0 is no flaming droplets, and d2 is high amounts of flaming droplets. The smoke and flaming droplets classification is added as a suffix to the combustibility classification. There is no smoke or flaming droplets classification for A1, because, by definition, a material that is classed as A1 does not burn, so there cannot be any smoke or flaming droplets.
Primarily we are interested in Part 1 of EN 13501-1, where we are looking to achieve A2-s1, d0 or Class A1 in accordance with the requirement from Approved Document B above, specifically regulation 7(2). Sometimes people talk about fl classifications such as A1fl. These are covered in part 12 of EN13501-1. The tests for floorings are actually exactly the same as for any other materials except that for floorings there is no test for the flaming droplets component (because a floor cannot form droplets as there is nowhere for molten material to drop to). We cannot use fl ratings for Aluminum decking because the droplets would be an issue for fire spread, and so this component of the test is important, and so we must test to EN 13501-1.
The testing regime for homogeneous products and non-homogeneous products are different. In summary, if your product is non-homogeneous (such as, it is painted), you must test the two components SEPARATELY, and they must each pass the criteria you need to meet.
Products achieving either A2-s1, d0 or Class A1 are generally referred to as non-combustible.
In order to achieve A2, there must be minimal sustained flaming (less than 20s), minimal change in mass, and very low (less than 50C) change in temperature in the test crucible.
In order to achieve the s1, d0 components, further testing is necessary to EN 13823. The smoke production needs to be very low and there needs to be zero flaming droplets for aluminum decking to be acceptable for non-combustible decking.
As with many parameters, the fire performance can be a trade-off for other requirements. For example, reducing the amount of paint on the product in order to improve the fire resistance, can (in the case of metallic substrates), make the product more susceptible to corrosion.
The Evolution of the requirement for Aluminium Decking
Prior to 2018, Approved Document B did not explicitly place any specific requirements on balcony decking. This is a highly contentious point, since arguably the functional requirement, coupled with the guidance in Approved Document B where over 18m in height (unless they were close to a boundary) buildings were permitted to use materials which were Euroclass C (in accordance with EN 13501-1) or national class 1 or better. Essentially timber decking would not achieve these requirements and plastic decking planks certainly would not. But there were not other obvious material selections available (aluminium decking did not exist for these applications) and so builders were using the commonly available materials (timber to begin with), and building control bodies knew this and were accepting these materials and hence this interpretation of the regulations. Timber rotted and warped in relatively short periods of time, and so plastic decking was made available which was much longer lasting than timber. In 2016 and even before this, serious concerns were raised by prominent figures such as Holland Shipp and Crowther of the BRE about combustible materials used in the construction of balconies.
Then, in 2018, when Approved Document B was updated in response to the recommendations made by Dame Judith Hackitt following the tragic events of the Grenfell fire. Specifically, Regulation 7(2) was updated to make it clear that the non-combustibility requirements also applied to a “specified attachment”, Appendix A of Approved Document B goes on to clarify that reference to a “specified attachment” includes balconies.
This gave the industry a challenge because balcony decking products simply did not exist for this purpose, or at least did not have the testing to verify the performance in accordance with EN 13501-1.
This also created a challenge for residents, because placing such onerous requirements on balcony decking essentially made it part of the façade, requiring specialist products and installation. Prior to this, residents would be at liberty to do what they liked with their balconies. Often the timber decking would rot and become unstable, so it was common for residents to arrange their own replacements, and to customise their balconies to their own preferences. Balconies were (and are) seen as an extension of the home, where (until 2018) residents were largely free to do what they liked with the fabric of their balcony, many often choosing to upgrade the rotting wood with plastic decking or even artificial grass. It has been seen in a number of notable fires that combustible materials used in the construction of balconies and fire load on the balconies from stored combustible materials have contributed to the spread of fires. For example, in May 2020, combustible materials on balconies contributed to the spread of fire up the outside of a building in Deptford. No one was injured, but around 50 people were unable to re-enter the building and had to be re-homed. Barbeques on balconies are a common cause of fires on balconies, and the London Fire Brigade has contacted a number of manufacturers who advertise barbeques for use on balconies, referring to these barbeques as a “staggeringly irresponsible idea”. But balcony fires aren’t only caused by such behaviours, seemingly innocuous activities can cause balcony fires. Smoking on balconies is common, particularly for tenants who are not allowed to smoke in their apartment. Carelessly discarded smoking materials can easily land on balconies below and ignite balcony decking surfaces and materials stored on balconies. Items which are often seen on balconies which can contribute to fire include carboard boxes, suitcases, plastic garden furniture and artificial grass. Plastic items on the balconies cause flaming droplets. These flaming droplets can be blown about during a balcony fire and cause the fire to spread downwards and across the building, whilst the leaping flames also cause the fire to spread rapidly upwards. The nature of balconies means that any fire on a balcony is well ventilated and easily spread by wind, so in a matter of seconds a balcony fire can spread upwards and across an entire elevation of a building. Heating of the glass of the adjacent windows may not cause them to break immediately, but the application of water can cause the windows to shatter due to thermal shock.
The necessity to use new construction materials for high-rise balconies also offers the challenge to manufacturers and specifiers that the system of standards doesn’t cover the types of materials that needs to be used on high-rise balconies. There are established British and European standards for timber decking, and plastic decking, but there are no standards for the non-combustible materials for decking like aluminium decking. The introduction of BS 8579 in 2020 brought some parameters which manufacturers and specifiers can use.
BS 8579 2020 was published on 28th August 2020 and offers guidance on the design of balconies and terraces. This British Standard considers the following design considerations for balconies and terraces:
The standard makes the distinction between a balcony and a terrace in that a balcony is an external amenity space above ground that is not above a habitable room but is accessed from the building. A terrace however is a roof and so there are usually habitable spaces above and below and there will be insulation somewhere in the build-up, either above the slab or below the slab.
Many of the parameters set out in the standard were in existence already but buried in another standards or guidance such as that from the NHBC which could have been easily missed by builders of projects which are not within the NHBC regime. The BS 8579 standard brings into focus some key aspects of balcony design and there are some new point’s introduced:
Structural standards are set out in existing standards and Eurocodes. But this new standard makes clear that some existing guidance can be applied to balconies by recognising that low natural frequencies can cause discomfort to the users, and proposes a minimum of 5Hz should be designed for. In addition, the standard clarifies that for reasons of comfort the finished surfaces should not deflect more than 5mm under a 2KN concentrated load.
The standard clarifies that dividers between enclosed balconies shall be fire rated to at least the level of the corresponding internal compartment rating. This requirement was commonly applied via interpretation of the guidance in BS9991, but now it is explicitly clear.
It is made clear that the floor of enclosed balconies shall have the same fire compartmentation performance as the compartment floors inside the building and where the balcony adjoins the building shall be stopped via cavity barrier or fire stopping.
Additional fire resistance is needed for balconies or terraces that form escape routes.
All parts of balconies on buildings which are occupied above 11 metres shall be of limited combustibility, i.e A1 or A2-S1-d0 as classified by BS EN 13501-1 in accordance with Regulation 7. Importantly, the standard introduces that this shall also apply to stacked balconies on buildings of any height.
An imperforate drainage tray beneath the finishes serves a further function to prevent flaming droplets falling to the balconies below.
The standard introduces the criteria that structural components shall provide fire insulation performance to the value of the cavity barriers or fire stopping in the adjoining structure.
The standard states that where this slab edge is thick enough, continuity of the fire stopping shall be maintained, but recognises that the slab edge is not usually thick enough to allow this; in which case the bracket shall incorporate fire stopping performance equivalent to the level achieved by the fire stopping or cavity barrier. The standard highlights that any such design shall only be suitable where test evidence exists to prove the performance of the bracket in continuation of the fire performance across the whole of the area where the balcony adjoins the building.
Particular consideration is needed around drainage penetrations in order to maintain fire compartmentation.
Finishes even to an enclosed balcony, shall be exterior-grade materials. The standard highlights the need for the longevity of components to be considered. The standard states that a safe method of replacing parts of the balcony shall be included in the design.
Balconies and terraces can be subject to high winds, especially due to proximity effects from the building, like those known as “funnelling”. During the design of balconies and terraces, consideration should be given to extreme wind events, and these should be mitigated to ensure that items do not become dislodged, and consideration should be given to the balcony doors. The standard states that where possible, balcony doors should be designed to open inwards or side where this is practicable, or in events where outward opening is the only option, restrictors should be fitted so prevent the door from being blown by the wind. Mitigation measures against wind can include:
- Specially designs balustrades
- Subdivision of the balconies
- Raised side balustrades
The guidance on level thresholds from BS8300 and Approved Document M is brought to light in the context of balconies with the 15mm threshold rule. The standard highlights that balconies and terraces to areas other than dwellings must accommodate the wheelchair tuning circle provision from Approved Document M. Gaps between the surface finish such as decking boards are limited to 6-8mm.
The standard highlights the consideration that has often been the complaint of residents of high-rise balconies, that the design should make them feel safe. As well as being intrinsically designed to address the required structural criteria, slip resistance is an important consideration. Slip resistance is determined by BS 7976. Depending on the environment, the most appropriate slider should be chosen to represent shod or unshod feet. In the relevant case, a PTV value in excess of 36 should be achieved in both wet and dry conditions in order to minimise slip potential to an acceptable level. The standard highlights that users should be advised of the need to maintain the finishes.
The design of the balustrades should minimise the opportunity for objects to fall from balconies. This is usually achieved by adding toe boards.
The standard states that an imperforate layer should be included within the balcony, in order to prevent liquids or solids falling through the gaps in the balcony and presenting a risk to people below, or that the designer should consider the risks in the designs where this is not included.
Where possible, replacement of components should be designed to be carried out from the balcony itself. A methodology for replacement should be detailed within the design. The standard identifies examples of components which may need to be replaced at the end of their service life, the example given is cavity barriers.
The standard introduces the requirement to provide a label on the balcony which displays the capacity of the balcony, in a manner that is easily understandable by the resident. This is somewhat abstract point which seems sensible from a design perspective, but almost impossible for a resident to practically utilise.
Balconies and terraces act as a source of heat loss and a condensation risk, as their components are often metallic and transmit heat well, which can have an undesired cooling effect to the structure. The standard highlights the importance of correct thermal separation, to avoid condensation, and to meet the thermal criteria of the building.
However, designs which collect the water in the aforementioned imperforate tray and channel this to the surface furthers from the building where it can run off the building are proposed, provided the balcony is not deeper than 2.5m
Also, positively drained solutions are proposed, however these are subject to the constraints of firestopping around the drainage pipes as highlighted above.
As highlighted above, gaps should be limited to 6-8mm between boards, and a 10 – 12mm gap should be allowed around the outside of the finishes in order to enable water to readily drain away.
The standard makes it particularly clear that no opportunity for even small amounts of water to be trapped on the finishes.
In line with NHBC requirements BS 8579 states that the drainage layer is noted to be at least 75mm below the threshold, and 150mm below the top of the membrane to adjacent walls.
Guidance is given on how to calculate the amount of expected rainfall on a balcony and how to design outlet pipework.
Balconies can offer some screening against unwanted external sound. Material selection plays an important part in the acoustic performance of the balcony. Solid materials should be used where possible for this purpose. Acoustic absorption of materials is classified by BS EN ISO 11654, with Class A being the best performing.
This standard is long overdue, but the guidance cited will not be news to most designers. There are a few points which some will find unusual, but this can often be the case where there is a gap in guidance and so designers will find their own tried and tested solutions. It could be argued that it is inevitable that any guidance introduced where there was previously little available, will set a collision course with the existing tried and tested solutions. In a time of #stayathome, and recladding projects going ahead, BS8579 2020 is certainly timely.
Moe recently, The Fire Safety Act 2021, Building Safety Act 2022 and the Fire Safety Regulations (England) 2022 have been published which provide further details about the design and management of buildings in relation to fire safety, with particular emphasis on high-rise buildings.
The Fire Safety Act paves the way for changes to the requirements currently in place under the Regulatory Reform (fire safety) order 2005.
The Building Safety Act 2022 makes further changes to clarify the position on who pays for replacement decking, when it creates a building safety risk. Up until now, decking has been mostly excluded from funding. Therefore leaseholders have been caught in a jam between a failed EWS1 form (or PAS 9980 report) which required replacement of the decking, and a process which will fund the cost of replacing flammable cladding but will not fund the costs of replacing flammable decking. Due to the access constraints and working at height etc, the replacement can be expensive, and leaseholders have found this challenging. The Building Safety Act seeks to give protection to leaseholders with new provisions which came into force on 28th June 2022 to protect leaseholders. We explain more about the legal framework for this in our Summary of The Building Safety Act 2022 in Plain English. But essentially there is a framework in place which makes the landlord responsible for taking action to rectify building safety risks. This is retrospective too, with protection going back 30 years. The intention of the Act is that, if it is a risk which was caused as a result of the building owner (or developer) then the person responsible for creating the risk has to put it right. This could pave the way for leaseholders to have a simpler transition to removing flammable decking and having it replaced with non-combustible decking such as aluminium decking or mineral composite decking. One might expect that where this is the cause, the cheapest compliant solution will prevail, but it is now set out in the Building Safety Act 2022, through the Residents Engagement Strategy, that leaseholders must be consulted and have their say on how building safety risks are managed, and so residents can make sure that their preferences on functionality, aesthetics and other requirements can be accounted for in the rectification works.
The development of these new product solutions was initiated firstly by companies who manufactured aluminium decking for other purposes which were able to pivot to fulfil the new demand.
How is aluminium decking produced?
Aluminium is produced from bauxite. Bauxite is mined mostly in Australia, but large volumes are also mined in China, Brazil and Russia. Usually close to the open cast mine, the bauxite is converted to alumina. This is done firstly by washing in caustic soda before being dried in a kiln. The alumina is then usually shipped elsewhere for smelting. The smelting process is usually carried out in a location where there is a good supply of low cost electricity. The smelting involves electricity being introduced through large electrodes made from petroleum coke and coal tar. In this process, the main products are CO2 and aluminium. The fumes are usually scrubbed in chimney stacks. The molten aluminium is then transferred via a crucible which is heated by gas burners. Aluminium has a relatively low melting point, so the crucible is maintained at around 600C. From the crucible, the molten aluminium is poured into moulds. The cast ingots are then usually cut to size before shipping to various extruders around the world. Most aluminium decking is formed by extruding. Specialist extruders which can process large profiles are used to produce aluminium decking.
The Millwood group were an established company making carports verandas and the like from aluminium. Part of their offer to make these kits from aluminium included aluminium planks. The group launched the Alideck brand and offer a range of aluminium decking products including the Alideck Junior (Alideck Jnr) and Alideck Senior (Alideck Snr). The Alideck junior and and Alideck Senior aluminium profiles are characterised by the raised (ribbed) portions, these are intended to provide slip resistance. Both the Junior and Senior aluminium boards are A2 fire rated, with a rating of A2-s1,d0. The Alideck aluminium decking boards are sold alongside a system of supports, cappings, flashings and pedestals. More recently Alideck have also offered a system referred to as Alipave, which is an aluminium substrate system into which tiles can be fitted.
Ryno were well known producers of plastic decking and plastic paving pedestals, and now offer the Ryno TerraSmart and Ryno Balcasmart systems as well as their Ryno ABD aluminium deck board. These systems can be specified with the traditional plastic decking pedestals, but Ryno also offer a metal pedestal also.
Envirobuild were an established provider of plastic decking and now offer a range of aluminium decking known as Envirobuild Hyperion decking. Envirobuild also offer a range of substructure systems and accessories.
Neaco have been manufacturing aluminium grilles for industrial applications for some time, and were able to adapt some of their products for use the balcony market. Neaco products are characterised by an industrial look ribbed profile and aluminium grille structures. Neaco have more recently released aluminium decking profiles with PPC coatings with patterns on them intended to create a more a timber deck appearance on the aluminium decking planks.
Most aluminium decking systems will come with various accessories. These can include flashings, cappings, stop-ends, various screws, paint touch-ups, isolation pads and clips. Flashings and cappings are needed where the ends of the boards are exposed, the capping and flashings are screwed to the cut ends to conceal the cut edge and make it look neater, provide protection from sharp edges, discourage insect nesting in the hollow portions and to prevent “bottle topping”. “bottle topping” is the phenomenon were wind blows over a hollow section and can create a humming sound. The various screws are needed to hold the decking itself in place, as well as the end caps and flashings. Some decking systems use a plastic clip. Plastic helps to reduce rattling of metal-to-metal surfaces of the aluminium decking planks and the aluminium rails beneath. The melting point and flammability of the plastic should be approved by the fire engineer due to the risk of decking coming loose or flaming droplets in a fire scenario. Isolation strips can be specified to protect against rattling also, and are often useful also to mitigate against electrolytic corrosion.
What is electrolytic corrosion?
Electrolytic corrosion (sometimes referred to as galvanic corrosion) when relating to aluminium decking is usually with reference to the aluminium decking being placed on a steel balcony frame. Electrons can flow through an electrolyte from the more negative (cathodic) metal to the more positive (anodic) metal. Water from moisture in the air, dirt, rainwater, seawater or stagnant water can act as an electrolyte. The effectiveness of water as an electrolyte is increased by contaminants such as salt and pollutants. The flow of electrons will tend to protect one metal and accelerate the corrosion of the other. Sacrificial cathodic materials can be used to mitigate electrolytic action, but the most effective solution is to avoid dissimilar metals or to keep them separate. Separation can be achieved via isolation materials. Careful choice of fasteners is also important to maintain separation of the materials.
Does Aluminium Decking burn?
Aluminium does burn but only at very high temperatures. Aluminium melts at relatively low temperatures. So in building fires, aluminium components such as façade capping’s are often seen distorting or falling away, but usually not burning unless it is a very intense fire.
Grades of Aluminium used in decking
You may often hear about aluminium being described as a particular grade, depicted with a four digit number, sometimes followed by a Tx reference, where x is another number, but what do these numbers mean? In the four digit reference, the first number is the grade, which is a number which corresponds to the type of metal that has been added to the aluminium in order to provide the characteristics that are required. The table below illustrates how this works:
|Grade of Aluminium
|Metals which have been added
|Resistance to corrosion
|1_ _ _ _
|2_ _ _ _
|Aeroplanes and military equipment
|3_ _ _ _
|Silicone, copper and magnesium
|Guttering, road signs etc
|4 _ _ _
|Cars and fabrication
|5_ _ _ _
|6_ _ _ _
|Silicone and magnesium
|7_ _ _ _
|8_ _ _ _
|Specialist additives such as tin
|Dependant upon the alloy, usually developed for a very specific application.
|Usually a specific use
As you can see from the table, the material properties significantly vary dependant on the alloys. Grade 1 aluminium is relatively soft, and can be worked easily and so it is used in electrical wiring because it is easy to bend and it has excellent electrical conductivity. It can also be work hardened easily, which can be good or bad, depending what you are using it for. Grade 1 can also be referred to as commercially pure aluminium. Grade 2 aluminium is often used where its high strength is important, but due to its relatively poor corrosion resistance it requires special surface treatment such as anodising as well as regular maintenance. For aluminium decking, grade 6 is most common because the strength is good, so less material is needed to achieve the required strength characteristics required. The addition of silicone lowers the melting point of the material and makes Grade 6 aluminium relatively easy to extrude, which keeps costs down when processing.
The number after the grade number refers to the amount of impurities in the aluminium. This is important as impurities can lower the consistency of performance and can also lower the corrosion performance. Then, the last two digits are a sequential number assigned to various grades. Therefore, there are hundreds of grades of aluminium, which a huge range of different properties. In aluminium decking, the grade of aluminium used is important as it must have good strength and excellent corrosion resistance.
The suffix Tx often quoted after the grade reference refers to the heat treatment that has been used. Heat treatments can be used to improve strength or ductility requirements. T6 refers to rapid cooling by water. Aluminium decking is usually T6 heat treated in order to improve strength.
Extruding aluminium decking
Aluminium decking is almost exclusively produced by extruding. The extrusion tool necessary to make the decking planks is comparatively large. If you think about the extruded aluminium components that you often see such as components for street signs, window profiles, door handles, or drawer runners these are all relatively small sections. Whereas the section size for aluminium decking is huge in comparison. This means that there are relatively few extruders around the world that can make these large extrusions. Extruding of metals has been around for a long time. The first extrusion process was actually used to make lead pipes.
In the most common aluminium extrusion method (known as direct extrusion), a section of aluminium is cut from the billet and this is then pre-heated using electrical heaters or gas until the whole section of billet aluminium is around 600 degrees Celsius.
A die is used, this is a machined tool usually made from steel which determines the shape of the aluminium extrusion. The die is also heated, usually using electricity, to around 500 to 600 degrees Celsius.
The hot billet is transferred into the press and then a powerful ram then presses the molten aluminium through the die to extrude it into the shape that is desired.
A puller is often used to also pull the extruded aluminium profile through the die. As it pulls the extruded profile out, in the case of aluminium decking (for aluminium decking a water quench is normally used) the section is drawn through a water bath in a process called quenching.
The section can be drawn via the extrusion process into very long lengths indeed. Standard lengths are usually used for ease of handling, so a saw blade is used to cut them into lengths for moving around the facility.
The sections are then placed into an area where they can cool down as they will still be extremely hot.
The heat and processing mean that the profiles can be distorted. The wide sections used in aluminium decking, if not cooled uniformly can distort. So a process of stretching is used to pull the sections back to within the acceptable tolerance.
The quenching process imparts stress into the material, and so, to optimise the strength characteristics a tempering process is used.
The T suffix means that the aluminium has been heat treated.
An H suffix means that the aluminium has been strain hardened to increase its strength.
An O suffix means that the aluminium has been annealed in order to make it more workable and increase toughness.
A W suffix means that the aluminium it has been treated to a process of natural ageing following a process of solution heat treating.
Aluminium decking will usually be heat treated in an oven, via a process called tempering. The number following the “T” tells us which of the ten different temper treatments has been used. For aluminium decking, T6 us usually used. This involves heating in an oven usually at around 400 degrees Celsius for four to eight hours, followed by quenching in water, cooling and then natural aging. This process removes internal stresses, which is intended to prevent the material from warping.
Following tempering, the material is cut to length for transport to the polyester powder coating (PPC) facility.
What is PPC
PPC stands for Polyester Powder Coated. Following the extrusion process, the aluminium decking profiles are what is known as mill finish. Mill finish is bare aluminium. Bare aluminium will oxidise creating a white powdery finish called aluminium oxide. Protection of the surface can be achieved by painting via a process known as powder coating. Coating of aluminium profiles such as aluminium decking is more complex than coating of steel, and aluminium decking PPC coating should be carried out to EN 12206-1 processes.
Therefore, powder coatings are applied to prevent corrosion, improve slip resistance and improve the appearance of the aluminium decking profiles.
Polyester Powder Coating uses dry powder, so the profiles are usually first drilled so that the aluminium decking profile can be hung up and electrostatically charged.
Most powder coatings are actually porous, and allow air and moisture through it, therefore it is essential that a rigorous process of pre-treatment is carried out to the aluminium prior to powder coating, or premature degradation can occur underneath the coating and cause it to flake off.
Good corrosion resistance can be achieved by pre-treatment using a chrome-based process, but due to the hazardous chemicals involved this is not normally used these days. Pre-annodizing creates the best level of enhanced corrosion protection but this is a comparatively expensive procedure. More recently, chrome-free pre-treatment processes to EN 12206‑1:2021 are available. The pre-treatment includes degreasing and usually an etching process which uses either a strong acid or alkali (or sometimes both processes in sequence), followed by oven drying, prior to the first coat of polyester powder being applied.
Following pre-treatment the aluminium decking profiles are usually hung up and electro statically charged so that the powder will stick to the primary face of the profile. The aluminium decking usually has a primary face and a back face, the reason for this is that the PPC process will take longer if the profiles will need to turned over, and so this would increase processing and raw material costs. Also, it is not desirable to apply too much PPC material to the profile as this can affect the fire performance of the completed profile.
The appearance and longevity of the final finish of aluminium decking profiles is highly reliant on the pre-treatment processes and quality of workmanship. Specifiers can use the Qualicoat industry scheme to check that they are specifying the appropriate corrosion protection and that a quality applicator is being used. When preparing the Qualicoat specification, it is important to take account of the proximity of the project to salt water. Projects near the sea or coastal rivers have additional requirements. The experts at the Qualicoat industry body explain that buildings within five kilometres of a coastal river or the sea should be specified with “seaside class” coatings, notably this includes most of London. The “seaside class” of coatings has a higher capacity to withstand corrosion in the face of abrasion due to airborne particles of dust and grit, and to deal with pollutants in the atmosphere including salt. Pertinent in particular to aluminium decking, powder coated finishes are especially susceptible to grit particles in the air because the surfaces are horizontal and so the particles can settle on the surface and collect in grooves in the aluminium decking profile. These grit particles usually comprise silica which can damage the coating, especially when stepped on, in-use and expose the aluminium decking profiles to the elements of the environment.
Any coating can be scratched, and chair legs, pets and general wear can cause scratches. A footfall test to TM391:2016 to 100,000 footfalls is a good indicator of wear resistance. Accidents do happen, and contact with a metal object can occur. Have you ever scratched something accidentally with a chair leg or a bicycle pedal? This type of scratch may not happen every day but it does happen, and thought needs to be given about what to do when it does. Some aluminium decking manufacturers offer a paint repair kit for touching up, this is usually a temporary solution or minor blemish repair whereas a professionally applied paint is a more permanent solution.
Slip resistance can be an important consideration especially if the area is part of a transit route, such as open terraces to blocks of flats. Ribs on the aluminium decking can help with slip resistance in the direction perpendicular to the direction of travel. Some tests have shown that ribs in the extrusion actually reduce traction in the direction of the ribs, the reason for this is the reduction in contact area. This has been proven by testing, but can also be seen in the world of motorsport, who could forget the rule change made in 1998 to introduce grooves in the formula 1 tyres in order to reduce traction, for the same reason (reduced surface area), the drivers experienced a marked reduction in traction in the 1998 season.
As an alternative to painting or coating aluminium decking, components can be anodized. Anodizing is a premium solution for corrosion protection and longevity of aluminium. The protective coating comes from the aluminium substrate itself. Prior to the process, the aluminium has to be chemically cleaned to remove oil and contaminants. A bit like electrolytic corrosion, the aluminium substrate acts as an anode and the cathode is usually at the side of the chemical bath. The substrate is then dipped into the electrolyte. The electrolyte used is usually sulphuric acid or chromic acid. Once in the aluminium decking plank is in the acid bath an electrical charge is passed through the cell and the oxidation process is accelerated to create a hard layer of aluminium oxide around all surfaces of the material. Anodizing is very good for corrosion protection because it affects all surfaces, whereas PPC and painting can only reach the surface that the operative can access during the painting process.
Aluminium decking profiles are usually produced in standard lengths and so it is necessary to cut the profiles at some point. The cut ends expose the inner material and so need to be painted. Therefore, a pack of touch-up paint which is colour-matched to the PPC coating is commonly available. Where aluminium decking becomes scratched and the PPC coating reveals the aluminium underneath, repairs to the PPC coating should be carried out by a professional. Incorrect painting of the aluminium can lead to premature corrosion, and there are chemicals involved in the process which are not usually suitable for domestic use. Most manufacturers of aluminium decking provide guidance on how this should be done, and can supply the touch up kit if needed.
Aluminium decking profiles are by definition hollow. These then need to be capped off at the ends and sides of balconies and terraces in order to shield users from sharp edges, and also to prevent “bottle-topping”, which is a phenomenon where wind blowing over a hollow section can create a humming noise. Open profiles can also provide a haven for insect infestation. Therefore, most aluminium decking manufacturers will provide capping pieces which can be screwed onto the ends or sides of the decking profiles in order to cap them off. These are usually supplied with the appropriate screws. It is usually advisable to fit these prior to fixing the aluminium decking planks down.
Aluminium decking profiles are usually held down by screws or clips. These will be normally provided by the aluminium decking supplier as part of the pack of components. These fixings need to be carefully specified to prevent electrolytic corrosion and ensure that the components don’t rattle in the wind or when being walked on. Sometimes mitigation factors can be provided to prevent these issues, such as plastic clips or rubber packers, these need to be checked by the fire engineer.
Alternatives to Aluminium decking
The traditional material to use for decking to balconies and terraces has been tropical hardwood. Tropical hardwood provides an aesthetically attractive finish, which could be easily cut and looked attractive even on the cut ends. The natural oils in the hardwood would help protect it and a range of chemical treatments could be applied prior to installation and periodically throughout its life to extend its appearance and useful life. An attractive quality of hardwood decking was that it would silver in the sun to create and attractive finish, and that any indentations or scratches caused by scuffs and scrapes in normal use seemed to provide an attractive patina which added to the authentic finish of the decking.
Hardwood decking has not been a viable option for high-rise buildings and areas with fire risks due to timber being combustible, and in any case, due to the timber being a natural material there are natural inconsistencies in the material which can cause warping and cupping. The use of tropical hardwood, contributed to deforestation of tropical regions. Even with responsible sourcing systems such as FSC and PEFC, this has been a contributory factor in the felling of high value trees in tropical areas.
Balau is one of the most common hardwood decks. Balau should be aged for a few weeks prior to installation in the location where it is going to be installed. It is also recommended that Balau is oiled immediately following installation, and then every 12 months afterwards. It is recommended to clean the deck with soda crystals regularly and brush with a stiff brush. Prior to re-treatment, a specialist cleaner is used to remove any dirt particles. This should be agitated with a brush prior to jet washing if possible. The deck must then dry fully before applying the treatment. During this period, any broken fixings should be replaced. Even when all maintenance requirements are followed, timber decks have a limited lifespan and require replacing periodically depending on the environment.
In response to these maintenance requirements, a range of plastic composite decks were available. These can be advertised as “Composite decking”, “WPC” (wood plastic composite) or recycled plastic decking. This family of products requires much less maintenance. But care must be used in installation to prevent cupping, warping and slippery finishes. The term “composite” refers to any combination of two or more materials. Sometimes it can be assumed that composites always contain some sort of polymer or plastic, but this is not the case. Composites can come in many forms and have a huge range of ingredients.
Plastic decking can vary significantly in cost and quality. If possible, it is always best to visit an installed deck which has been installed for a number of years prior to making a final decision on the specification. Plastics tend to have a large thermal expansion co-efficient, which means that they get longer when heated, this is difficult to manage with deck planks, as this necessitates special sliding fixings and that the boards have gaps between the ends of the boards.
Following the change to the building regulations in 2018, timber and plastic decking is no longer permitted on tall buildings and in other high risk buildings due to the materials being flammable.
Aluminium decking is a viable alternative to these materials, and certain aluminium decking profiles have been specifically tested to ensure that these pass the stringent combustibility requirements now demanded by the building regulations.
Blazeboard has been in development since the advent of aluminium decking. Blazeboard is a mineral decking board which exceeds the combustibility performance demanded by the latest version of the building regulations and offers an alternative to aluminium decking. Where architects and specifiers are seeking an alternative to the modern aesthetic of aluminium decking, and seeking a more traditional look and feel, then Blazeboard delivers a more homely and traditional alternative to aluminium decking.
Installation of aluminium decking and mineral composite decking can be very different. At first, the installation of aluminium decking was daunting for many installers as this was a completely different material from what they were used to. Different blades were required on the saws for cutting metal, and new techniques and new processes including painting and capping, but most installers became proficient with aluminium decking once they had been trained and done a few installations with appropriate support.
Blazeboard mineral composite decking installation is different to the installation process for aluminium decking, but more similar to the installation of traditional timber decking (except Blazeboard does not need any conditioning or treatment). The Blazeboard installation process also does not need any painting or capping. Similarly to aluminium decking, most installers are initially hesitant about the installation of Blazeboard mineral composite, until they have been trained and installed some of the material under suitable guidance, and then it becomes second nature to create high quality installations.
For bolt-on balcony installations, firstly check the spacing of the balcony supports against the support span specified for the aluminium decking board. Each decking board specification has a maximum span which must be complied with. For example, the Alideck Lite has a maximum span of 400mm. Decking manufacturers will provide span tables upon request. Supplementary support joists can be fitted as part of the aluminium decking system where specified. Some aluminium decking boards have a sub-rail profile which is fitted first to the balcony frame, for the decking boards to attached to. Some other aluminium decking boards can be fixed directly to the balcony frame.
Setting-out of the aluminium decking boards should be planned before starting the balcony installation, and if possible the balcony should be drawn and planned before starting. Some manufacturers will pre-cut the decking boards to the drawing before delivery. In this case it is even more important to start from the defined point and work out from there.
The substrate should be checked for integrity and completeness and any combustible materials shall be removed such as leaves or debris. Aluminium decking can be susceptible to heat build-up in the void below the decking, so ensure to follow the decking manufacturers instructions to prevent heat build-up in the void, sometimes a minimum gap is required.
Also ensure that any accessible items below the decking will be accessible when the deck is complete such as gulleys. This can be achieved by making cut sections of deck around the gulley which can be unscrewed to clear out the gulley periodically.
A setting-out point should be established, usually this is by the balcony door. Boards should be installed with a 10mm gap at the end to allow for drainage and expansion, and gaps between the aluminium decking boards should be set in accordance with the manufacturers specification and BS8579. This is usually a minimum of 5mm drainage gaps between boards and a maximum of 8mm.
If it is required to cut boards along their length, ensure to observe the minimum width specified by the aluminium decking manufacturer. If the minimum width cannot be adhered to, it is advisable for the cut boards to be equalled across the front and back of the balcony.
Any cut ends of aluminium decking boards are required to be painted in accordance with the manufacturer’s instructions to prevent corrosion. Then the end-caps and trims are then screwed in to cap off the cut ends in aluminium decking boards. Expansion gaps at the end of aluminium decking boards should be allowed for thermal expansion. The longer the decking boards, the greater the gap is needed, this should be in line with the aluminium decking manufacturer’s specification.
Mineral fibre decking boards such as Blazeboard do not require painting at the ends of the boards and no capping is needed. Also, expansion gaps are usually not necessary on mineral fibre boards as they have a much lower thermal expansion coefficient than aluminium decking boards.
It is important that the manufacturers specified fixings are used in accordance with the aluminium decking manufacturers instructions. These fixings will usually be provided with the decking kit. Some kits require the clips to be fully aligned before the deck board is placed, and then the clips should be engaged sequentially. Usually it is advisable to fit the first line of clips to only half tightness until the second row off clips is fitted, and then it is essential to return to the first set to ensure that they are tightened fully. Loose clips can cause rattles on the aluminium decking, this can be exacerbated by over tightening of the screws.
In order to achieve a high quality finish, it is advisable to protect the aluminium decking boards as installation progresses, to prevent scratches to the polyester powder coating.
Usually it is possible to fit aluminium decking and mineral composite decking directly to the balcony substrate, but the spans need to be checked first, and any combustible materials should be removed first. Note that many balconies include elements of timber in their construction as well as the existing decking, these elements should normally be removed, firstly because they are combustible and will not meet the requirements of Regulation 7(2) and will be an unnecessary hazard in any PAS9980 risk assessment, but also simply that any timber substrates will likely rot and come to the end of their life before the new aluminium decking does, so you could find that your new aluminium decking needs to be removed well before its lifespan because the substrate has failed. Most aluminium decking distributors as well as the mineral composite decking manufacturers can provide a substrate system to replace any timber in the substructure of the balcony.
Cutting around features such as balustrades and downpipes neatly is critical to achieving a high quality finish. If possible a template should be used, to avoid over cutting. A good tip to avoid over cutting is to drill a hole in the aluminium decking and cut towards the hole. This also provides a curved corner to your cut-out in the decking, which provides a neat finish. You can adjust the radius of the curve by selecting the appropriate drill bit. Cut edges in the polyester powder coating should be touched up in accordance with the manufacturers instructions. These tips are intended for aluminium decking, but they are also highly effective for mineral composite decking as well, but where you must use a good quality drill bit for metal substrates to drill aluminium decking, a “multi-construction” drill bit will work effectively on mineral composite decking.
Note that when cutting aluminium decking, always follow the manufacturers instructions and site guidance to create an appropriate risk assessment and method statement. This will include the use of suitable eye protection to protect against swarf, suitable gloves to protect against sharp edges as well as hearing protection and possibly a mask, boots and hardhat depending on the site rules as well as the risk assessment and method statement. Take caution if cutting on the balcony, shards of swarf from the aluminium decking can be very hot and could land on combustible materials below. If removing decking over the whole balcony is necessary, it is likely some fall arrest protection is necessary, it is essential that there is a suitable risk assessment and method statement in place for work at height and personnel must be appropriately trained and take necessary precautions to prevent falls and falling objects.
What is the difference between a terrace and a balcony?
A balcony can be projecting or in-set, whereas a terrace will be on a roof, and where it has accommodation space below it, there will usually be an insulation layer within the build-up.
The build-up necessary for a terrace will vary depending upon whether the build-up is a cold roof, warm roof or an inverted roof. The simplest type of terrace construction is where there is a cold roof. In a cold roof, the insulation is installed below the roof structure. Therefore, the pedestals will sit directly on top of the roof structure and hold the joists. The aluminium decking or other non-combustible decking can then be fitted to the joists. As with most things in construction, the devil is in the detail. Pedestals sitting on waterproofing can present a number of challenges:
The waterproofing surface is usually laid to a fall. Therefore it is necessary for the pedestals to be adjustable so that they can be different heights, to cope with the sloping roof surface whilst keeping the aluminium decking surface level. Some decking with particularly thick ridges may need to be laid to a slight fall to let the water drain out from between the ridges, but aluminium decking with particularly deep ridges can trap snow, ice or even simply some dirt or moss, these ridges cannot drain and so ice and more dirt or moss can build up between the ridges. Assuming that the decking can be laid level when in keeping with the manufacturers instructions, the pedestals will need to be different heights to accommodate the slope. There are a few ways of adjusting the pedestals, some can be twisted on a thread, but the adjustable aluminium pedestals which are faster to install are those where they attached to the joists with a serrated channel, and overlap the channel by the desired amount to achieve the required height. Whichever pedestal you chose for your aluminium decking, it is important that the pedestal height can be locked in position once selected so that it cannot move once the desired height is set.
The fall will usually mean that the pedestal is not truly vertical. With many pedestals this can mean that the pedestal is not stable. This is a problem for aluminium decking systems and a more serious problem for paving systems because the paving on top is usually loosely laid. This means that the walking surface on the tiles can feel slightly unstable, and over time will mean that the paving slabs or tiles will become uneven. Some aluminium pedestals have slope correction to overcome this issue, this usually involves turning an adjustable disc at the bottom of the pedestal in order to make it upright on a sloping surface. Another method of correcting for sloping roofs is for the pedestal to be designed to cant over, and then there are two or sometimes four fixings in a channel at the top, this means that the pedestal is then locked in position at a slight angle, this design works very well also. Pedestals are available from aluminium decking providers like Alideck and MyDek, as well as pedestal specialists like Buzon.
Waterproof membranes are notoriously fragile, and as such it is important that a protection component is installed first in accordance with the waterproof membrane manufacturers guidance. Waterproofing membranes also have joints in them, this coupled with the fact that the substrate is rarely flat, means that the waterproofing membrane is almost always bumpy. This means that it is doubly important that the pedestal position is locked in place with mechanical fixings to the joists as described above otherwise the pedestals and hence the aluminium decking assembly or paving or tiles will usually wobble at least a little.
In warm roof designs, it is especially important that the aluminium decking pedestals are placed on spreader plates in accordance with the recommendations of the waterproofing manufacturer. This is because in warm roof designs, the insulation is on top of the structural layer, and the waterproof membrane is laid on top of the insulation. So, if the load is not spread appropriately (or the incorrect insulation layer is used which doesn’t have sufficient loadbearing capacity), then the waterproof membrane can be punctured which will lead to water leaks. It is also important to consider the temporary condition during construction. Construction of an aluminium decking or any other kind of terrace involves cutting and potentially sharp edges and heavy footfall and therefore it is possible that the membrane could become punctured during the installation of the surrounding works before installation of aluminium decking or other decking or walking surface. Therefore, for warm roofs it is especially important to check the manufacturer’s instructions of the insulation and membrane before specifying the aluminium decking build-up.
It is usually impractical to mechanically fix pedestals through the waterproofing. Therefore, it is important that the top of the pedestals are mechanically fixed at the top so that they don’t move. This is less of an issue for aluminium decking because the decking is usually fixed down with screws, likewise for mineral fibre decking, as this is also usually fixed down with screws and so the decking boards should not move. But it is common for paving slabs or porcelain tiles to not be mechanically fixed, this means that they can move. Even a tiny movement means that un-secured tiles can “walk” out of position over time, and create trip hazards and chip the tiles at the edges. The best systems use an aluminium joist to connect the pedestals together so that the pedestals and the walking surface are securely fixed and cannot move. This works for aluminium decking, mineral composite decking as well as porcelain tiles and paving slabs.
The joist should be at least 6mm off the waterproofing membrane otherwise the roof will not drain properly, and water can become trapped, which can cause a myriad of problems including deterioration of the concrete structure. The build-up must also not be too high otherwise the height of walking surface will be too high, and the balustrades will be unsafe. Handrails should usually be at least 1100mm above the walking surface. Refer to Approved document K for guidance on the minimum height of handrails. Note that this is a minimum, and should take account of other risk factors such as wind and likelihood of children climbing on adjacent objects, and so in many cases a higher handrail may be appropriate. If there is a step above the walking surface, close to the handrail, measure the height from the top of it rather than the walking surface.
The build-up height is also important so that there is sufficient drainage. Usually, the waterproofing layer should be at least 150mm below the walking surface, and 75mm at doorways. The walking surface of the aluminium decking should ideally be placed at the same level as the floor inside the building at doorways, and a minimum threshold step should be maintained. Approved document M recommends a maximum upstand at the threshold of 15mm. Therefore, it is important to ensure free drainage of water to the drainage layer below. This is usually achieved by leaving a 10mm gap between the aluminium decking and the threshold. Drainage can also be further facilitated in high moisture areas such areas susceptible to wind driven rain or in wet areas such as leisure areas, where a threshold drain may be more appropriate.
On small balconies etc it makes little difference which way the boards run, unless you have a particular type of aluminium decking with large ridges on it, where you may want to direct the ridges way from the door so that they drain water away from the doorway. But in all other cases, for balconies at least, the board direction is really an aesthetic choice, or dictated by the structure of the balcony. But in large terraces or walkways, where there is a public walkway, most aluminium decking manufacturers recommend that decking should be laid perpendicular to the direction of walking. This provides for better drainage and better traction in adverse conditions.
Inverted roofs are where the membrane is below the insulation. This means that the insulation is either laid between the aluminium decking joists, or the aluminium decking joist system is fitted on top of the insulation. In the latter example, it is doubly important that the insulation cannot move when installed, and as recommended above, that the aluminium decking joist system is mechanically fixed together so that it cannot flex if the insulation is not perfectly flat (the insulation is almost always not flat). The stability issue challenge can be exacerbated during high rainfall. During high rainfall it is not uncommon for flat roof designs to become waterlogged, this can cause the insulation to float, and if the aluminium decking system is not rigidly fixed together, the moving insulation can move about the other components and compromise the integrity of the system. The aluminium decking system should not float in the event of the roof becoming flooded, or the surface could be hazardous for users stepping onto what appears to a solid aluminium deck. This is especially a consideration where paving has not been fixed as the floating insulation can knock the pavers out of position. Laying the insulation between the joists sounds like the simplest solution so far, but the aluminium decking pedestals will act as a cold bridge, and so could affect the efficiency of the insulation and as such more insulation may be needed than otherwise would be the case, an architect or insulation specialist will be able to carry out a U value calculation on your build-up to verify whether this is an issue or not.
Tall buildings can create localised wind effects which can be difficult to predict. These can create pockets of updrafts where the wind flows up and over a building. These forces can be significant and can be sufficient to suck furniture and tiles off balconies. It has been seen on occasions that tiles or furniture has been thrown to the street below due to a freak wind event. To mitigate against this, any tiles or pavers which are not mechanically fixed and are relying on self-weight should be at least 40mm thick. The best solution is for all components of the system to be mechanically fixed down, such as is the case on aluminium decking and mineral composite decking systems.
Items stored on balconies
Consideration should also be given to the items stored on balconies in terms of combustibility and wind uplift. Lightweight furniture can be tied down to tiedown points. Tie down points can be screwed into aluminium decking or mineral composite decking, and the furniture can be tied to these with straps when not in use in order to prevent the furniture from blowing off the balcony.
Consideration must also be given to the combustibility of items stored on balconies. Any combustible items can be ignited by discarded smoking materials from balconies above, or glare from windows. This then serves as a rapid source of flame spread up and down the exterior of the building. Items often stored on balconies include obvious items such as furniture but very often balconies are used as surplus storage which can present a significant fire load, luggage and boxes are a common feature on balconies. Finishes such as artificial grass and dried plants are a significant fire threat also. Plastic items are a particular threat because burning droplets can be blown from the balcony in a fire an spread the fire downwards across the building as well as the progress of flame upwards from one balcony to the next. Whilst aluminium decking and other types of non-combustible decking are a huge step forwards in fire safety; incorrect storage of combustible items on balconies is still a threat to safety.
Now that we have seen how aluminium decking is made and should be designed it can be seen that there are many important considerations to take care of in the design of a deck or terrace and we have also looked at some of the alternative options. It has also been highlighted that as well as high-rise balconies, aluminium decking or mineral composite decking can be the safe choice for longevity and utility as well as simply being a safety necessity in a range of scenarios.