Key Points About Balcony Lifespans
- Balconies are one of the few structural elements exposed to weathering.
- Balcony lifespans depend on maintenance and mid-life replacement.
- CAB say the recycling rate for architectural aluminium is 92- 98%, as only 5% of the original energy is required to recycle it.
Guidance in BS7543 Table 1 suggests different categories of ‘design life’ for the different building components and structures. Most external cladding, windows and doors are categorised as ‘maintainable’… Foundation and structural elements are categorised and ‘lifelong’ and therefore should last the life of the building.
Building structures should typically be designed for ‘normal’ 60-year lifespans. It is generally anticipated that the structure will last longer than this. However, it should be considered that the structural elements of a balcony (unlike most other structural elements of a building) are exposed to weather conditions and not protected by the façade. Balcony designers and specifiers, therefore, need to give careful consideration as to what will happen to the balconies when a building reaches the end of its design life.
Regular maintenance to improve balcony lifespans
Regular maintenance is covered in the following section. The two which could perhaps cause more of an effect on balconies lifespans are:
- The build-up of dirt in drip trays and gutters, causing water to back up. This should be addressed through a regular cleaning cycle.
- Local deterioration or damage to PPC. Whilst specification of a coating application which has good pretreatment is essential, if issues occur, they should be addressed quickly from access equipment or abseiling to prevent spreading.
Mid-life replacement of parts to extend balcony lifespans
Most buildings typically get some element of upgrade or refurbishment during their service life. Often, it is to bring old buildings up to the performance of the ever enhancing building products being used in new constructions. If the balconies are included in such works, our Cassette® balconies could include:
- Decking – this is most likely to be done in situ, where existing boards would most likely be required to cut the decking to shorter lengths to get it up the building and through the apartment. With using WPC clipped decking systems, boards can be individually removed without having to find and remove standard decking screws.
- Glass damage or delamination – dependent on the level of damage, the replacement strategy can be used to replace individual panels or, where several panels may be damaged, the balcony can be lifted down to ground level to carry out the work before gliding them back onto the existing arms.
- PPC – again it depends on the environment and the amount of damage a balcony may have been subjected to. More minor damage can be done in situ, whereas widespread breakdown due to end of PPC life may require balconies to be lifted to ground level to replace or recoat parts. Most standard Cassette® balconies have individual drip trays and fascia’s which allows individual components to be replaced where damage is limited to certain parts.
- Crevice corrosion of fixings – at such points, replacement of fixings used for key components should be considered for replacement.
Future upgrade to extend balcony lifespans
Our Cassette® balconies are continually being developed to enable ease of replacement and design consideration has been given to how additional elements could be incorporated later. Perhaps one of the drivers of such a scenario could be where several separate safety incidents involving balconies lead to regulations changing to incorporate additional safety measures, e.g. increasing the balustrade height and clients choosing to upgrade existing balconies to the new guidelines.
Long term corrosion
As shown in the graph below, galvanised steel deterioration over time depends on the thickness of the coating and the environment in which it is applied.
BS EN ISO 1461:2009 (Table 3) guidance shows that steel greater than 6mm thick should have a minimum mean coating thickness of 85 Micron (μm). Assuming that corrosion happens in line with the graph’s typical corrosion and that an arm has a 85-micron coating, a balcony on a building on the Greenwich Peninsular, for example, is likely to be at the end of its service just before the ‘normal’ service life. This is one of the reasons we have chosen to move away from steel bolt on balconies and develop Cassette® balconies in aluminium.
Service life of hot-dip galvanized coatings as a function of zinc thickness and specific environments.
End of life
Aluminium and steel can both be recycled. Aluminium, however, is one of the easiest metals to recycle; according to the Council for Aluminium in Building (CAB) the recycling rate for architectural aluminium is between 92-98% as only 5% of the original energy is required to recycle aluminium. They also suggest that 75% of all aluminium produced since the 1880s is still in use. Other key components such as WPC decking products are also able to be recycled.
Recycling is only possible if the balconies can be easily taken down. Like the ease of install, removing a balcony from the building can be taken off and because it is constructed using mechanical joints rather than welds, it is much easier to disassemble.
Galvanic Corrosion – Key Points
- Avoid contact between dissimilar metals
- Avoid a difference of more than a 0.015 anodic index value
- Use isolators to avoid electrical contact between metals
Galvanic (or bi-Metallic) corrosion is the preferential corrosion that occurs when dissimilar metals are in contact in the presence of an electrolyte. The effects are like conventional corrosions of a single metal but generally proceeds at a higher rate depending on the difference in electrochemical reactivity of the anode and cathode metal.
The intensity of galvanic corrosion is affected by the electrolyte pH and conductivity and occurs when there is:
- An electrolyte bridging two metals
- Electrical contact between two metals
- A difference in potential between the metals to enable significant galvanic current
- Sustained cathodic reaction on the more noble of the two metals
One way is to electrically insulate the two metals from each other (e.g. using plastic insulators). Unless they are in electrical contact, there can be no galvanic corrosion.
Another way is to keep both metals dry (e.g. powder coating), or coating the more noble (the material with higher potential).
When contacting metal’s potentials are closely matched, the galvanic current is less, reducing the corrosion. Using the same metal throughout is best, but externally avoid more than .015 V difference in the “Anodic Index”.
We use isolations between galvanised arms and the aluminium frame of the Glide-On Cassette balcony structure.