Wall copings are an integral part of any building structure, providing a watertight protective barrier for parapet walls and roofs. Copings don’t just cap the top of a wall, but come down both sides, encasing it and adding extra protection all the way around. Copings can be flat-topped or given a slope that encourages surface water run-off.
Individual coping sheets must interlock and seal in a way that prevents water ingress. They also need mounting to the wall in a way that will withstand decades of wind and rain.
To ensure the best possible fit, many applications require bespoke aluminium fabrications, such as on curved walls. Skilled aluminium fabricators measure and shape each piece individually to achieve an efficient engineered coping solution.
In this guide:
- Why are copings important?
- Considerations for specifying wall copings
- Aluminium vs. other coping materials
- The benefits of aluminium for copings
- How thick do aluminium copings need to be?
- Aluminium copings and wind-rattle
- Powder-coated aluminium copings
- Are aluminium copings fire-rated?
- What are Secret Fix copings?
- Why use Secret Fix copings?
- HJA Fabrication’s Secret Fix coping system
Why Are Copings Important?
Many buildings today have parapet walls on the roof, whether a pitched or flat roof. A parapet wall is an extension of the exterior or dividing wall that extends up above the roof.
Water naturally runs off a pitched parapet wall, however, horizontal walls need a coping as it is an integral part of the building envelope, protecting it from the outside elements.
If there’s no coping, water will rest on the top surface and soak into the porous brick. Mortar joints also create opportunities for water ingress.
On brick walls, water ingress can lead to efflorescence (a form of salt) that stains the outer surface. A more serious problem that shows up as so-called rising damp is when water soaks down through the wall. Eventually, it can lead to plaster or rendering coming away and rot or corrosion in structural components.
Copings solve these wall-covering problems, directing water away from the building, and also providing an attractive topping to parapet walls.
Considerations for Specifying Wall Copings
When specifying wall copings for parapet walls and roofs, certain things must be considered that are unique to each building and its location. Coping are a functional and protective component of any roof structure so must be effective, durable and strong.
Initially, you must consider the environment of the coping, including weather, sunlight, and temperature.
With wind, you must consider the strength of it at the height of the roof. Gusts of wind in the UK have been recorded as high as 150mph. This is a particular problem in exposed locations, especially along the coast.
As wind travels up the side of a building it can create a vortex, further amplifying the force. This can be destructive if it is captured under the coping as well as incredibly unsafe for people below.
Knowledge of peak wind speeds will inform how a coping should be fixed to the wall. A strong coping attachment must be considered.
Also, rainwater must be considered. If water will pool at the roof, an incline might be best to divert it. Wind can blow rain horizontally and even upwards, so your coping must be watertight to the wall and protect against this.
Finally, sunlight and variation in temperature are particular challenges when using metal copings. Thermal expansion and contraction must be factored-in to both the fixing methods used and the joint design. Repeated expansion and contraction can cause a coping to fail and also let in water.
Aluminium vs. Other Coping Materials
No coping will last forever, but some will go longer without maintenance than others. If there won’t be much opportunity to carry out maintenance or it will be hard to do, greater priority should be given to low maintenance coping systems.
As aluminium is naturally corrosion-resistant, it is more long-lasting than other coping solutions.
Additionally, aluminium has a higher specific strength (strength per kg) than steel, so copings made only 2 – 3mm thick are strong enough to resist deformation. This makes any aluminium coping system a great option for a building envelope.
But what about the other material options for roof copings?
Stone, tile/terracotta and lead have long been standard choices for copings. Each can provide an attractive look but all three are heavy material choices, impacting installation as well as the roof structure. Similarly, tile and stone copings are usually fixed using mortar, which can suffer from freeze-thaw damage.
Another option for copings is GRP and Polymeric copings. They are lightweight and can be shaped easily. Unfortunately, these material choices can deform under heavy loads, or in high winds, due to their limited strength. They are also vulnerable to UV deterioration.
Metal copings are a very popular option as they have more strength. Mild or plain-steel copings can be easily fabricated but corrosion can be a problem with rust streaks being unsightly on buildings. Likewise, copper is attractive when first cut but oxidizes with a layer of green verdigris. (Modern alloys and coatings can postpone oxidation but not prevent it entirely.)
Therefore, we are left with aluminium. Aluminium copings are protective and attractive, can be powder-coated any colour, and are a cost-effective while still sustainable option.
The Benefits of Aluminium for Copings
Aluminium Copings Provide Protection
A skilled fabricator can form aluminium wall copings into almost any shape needed.
They can follow a curved or meandering wall, can be fitted to corners of any angle, and can be given a radiused or sloped top for good drainage. This makes aluminium copings an ideal option for protecting parapet walls from the weather.
Aluminium Copings Offer Strength and Durability
Aluminium is a ductile and adaptable metal, whilst also being extremely corrosion resistant.
It’s also surprisingly strong; a kilo of aluminium is stronger than a kilo of steel. That strength means aluminium copings can withstand heavy rain and strong wind.
In short, when you put aluminium to work protecting your structure it’s going to last without regular maintenance.
The Appearance of Aluminium Copings
One of the great things about aluminium is it can be easily and effectively coated with a variety of solutions from paint and powder coating to even anodising.
This gives architects unlimited opportunities for the style of coping system they want, and whether it will match or contrast the other architectural features of a building such as windows, doors, soffits, fascias, and cladding.
Installation of Aluminium Copings
Thanks to the strength of the aluminium, coping pieces only need to be 2 to 3 mm thick. Coupled with relatively low density (for a metal), this results in pieces that are easily raised to rooftop level.
This helps speed up coping installation and can lead to significant cost savings. (Would you rather be lifting stone pieces to the top of the roof?)
In some applications, lightweight copings may offer structural advantages too, especially when compared against the mass of stone or concrete otherwise needed.
How Thick Do Aluminium Copings Need to Be?
Strong winds impose high loads on copings. If not appropriately secured, there’s a risk of them separating from the wall, with potentially very serious consequences.
The most likely failure mode is the coping pulling through the fasteners. That’s why it’s important to use aluminium coping of sufficient thickness.
When formed into copings, large flat areas made from an aluminium sheet that’s too thin would have a wavy, uneven appearance. This looks unattractive and could lead to water pooling.
This means there is a minimum thickness for aluminium copings. Design manuals for architectural fabrications suggest a thickness of 2.00 mm for coping widths up to 550 mm and 3.00 mm for those stretching to 650 mm.
There may be situations where thicker sheets are needed but this will make the coping harder to cut and form. Consequently, not only will you need to pay more for the extra material, but you’ll also be paying for the added work involved in making your coping.
Aluminium Copings and Wind-Rattle
The issue with wind is not so much horizontal speed as the vertical force or uplift that it can exert on the coping. Wind can hit the side of a building at a standard speed, but it then accelerates as it drives up the side of a building, repeatedly catching underneath copings.
In Europe and the UK, there are no official standards for wind testing copings. The US however has an ANSI/SPRI/FM 4435 ES-1 pull-off test, and the UK’s Building Research Establishment (BRE) has developed a testing procedure that takes a similar approach. You can read about this in our blog “How are aluminium copings wind tested”.
Many coping installations on residential properties get the same complaint – rattling in the wind. Copings can be noisy, either rattling in high winds or creaking in hot temperatures as they expand.
Both of these issues must be addressed through appropriate fabrication and installation.
Your first priority should be to work with professional-grade aluminium fabricators. They will be able to perform engineering calculations that are specific to the needs of the installation, ensuring high quality.
Here we will highlight how aluminium copings can prevent wind rattle and give peace of mind to building tenants, whether day or night.
Copings must be spaced accurately, with components not too long to encourage vibrations. Post spacings should be 48” on the centre or better, to evade wind rattle.
We also advocate avoiding the use of pass-through pickets. Even if your railing pickets are welded onto the top and bottom rails, vibrations and rattling can still occur if they are not welded or otherwise firmly affixed to the pass-through component.
We do commend the use of rubber strips and adhesives, as well as anti-rattle foam. These components are weatherproof any gaps that may be letting wind whistle through, as well as water ingress. We advise that rubber strips and adhesive may need to be replaced periodically.
Powder Coated Aluminium Copings
Powder coating is a technique mainly used to apply decorative and protective finishes to aluminium profiles. This is done through a process that electrostatically charges the powder, consisting of a mixture of finely milled resin and pigment. This is then sprayed on to the aluminium extrusion. It is then fused into a smooth coating in a curing oven.
A highly versatile aluminium surface treatment option, powder coatings offer several advantages in any application. Powder coating is durable and weather resistant.
Additionally, powder coating is available in a wide variety of colours, including matt, satin and gloss, as well as metallic finishes. And, if for any reason dents and scuffs appear on the coping, they can easily be repaired using a matching colour liquid coating.
Adding colour to your coping system can be an easy way to convey a sense of uniqueness to your building, and consistency with the rest of the architectural fabrications.
Are Aluminium Copings Fire-Rated?
As a material, aluminium can offer effective protection against fire, making it the preferred choice for copings intended for specifiers working on a range of different applications.
The key material property of aluminium that makes it fire-resistant is that its melting temperature is about 660°C. This, combined with the high heat transfer and reflectivity properties of aluminium, contribute towards reducing the impact of heat on the building structure.
In other words, when aluminium is exposed to fire, its high thermal conductivity means that it can quickly dissipate large amounts of heat from the flame and absorb even more thermal energy. This ‘cools’ the environment and restricts ‘very hot spots’.
Therefore aluminium offers a comparatively higher response time to firefighters and is an ideal choice for architectural copings.
What Are Secret Fix Copings?
Wall copings are an architectural element where appearance is almost as important as function. From an aesthetic perspective, it adds a finishing touch to a parapet wall.
When specifying aluminium copings, choosing a Secret Fix coping means the fixing is hidden from view but still maintains its durability.
Why Use Secret Fix Copings?
The main benefit of Secret Fix copings is to avoid the many drawbacks of installing fixed aluminium copings. Fixed copings often fail due to the pressure they face from years of expanding and contracting on hot days and cool nights. When constrained, the pressure causes it to bow in the middle and deform those fixed fastenings.
Secondly, the fixings of standard copings require holes to be drilled through the top of the coping. This, however, becomes an entry point for moisture and rain.
On Secret Fix copings, the coping itself is not bolted to the wall, but a bracket is, which the coping attaches to. This means the finished coping has a clean aesthetic whilst also benefiting from having no holes going straight through it.
The bracket is extruded in a way that allows the coping to clip-fix to it. The brackets are bolted to the wall and then the coping is pressed securely on top.
HJA Fabrication’s Secret Fix Coping System
Our Secret Fix copings are proprietary, but we can highlight some of the key benefits they provide.
HJA’s Secret Fix copings are protected against water penetration due to polymer gaskets that are integrated into the brackets. These also prevent wind rattle, along with anti-rattle foam.
Due to the way secret fix copings clip into place, they’re much faster to install than any other coping fix system available. This allows construction workers to fit more copings in a shorter period of time, making them more efficient.
As for wind-resistance, the HJA Secret Fix aluminium coping system has been independently wind-tested to 144mph.
The HJA Secret Fix copings offer an attractive, low maintenance coping system that is simple to install yet both rigid and secure. The out of sight coping fixings provide a smooth, fastener-free appearance that any architect would desire.
Get in touch today to learn more about our aluminium and Secret Fix coping solutions. Fill out the form below!
