The Met Office says there’s no conclusive evidence that winter storms are getting stronger. However, they warn that near surface wind speeds are likely to increase in the future.
This has implications for architects, civil engineers and builders. To avoid storm damage, be sure to use materials and coping systems that stand up to high winds. Secret Fix aluminium copings from HJA Fabrications are one of the best products to use.
Weather Protection With Aluminium Copings
Copings are the toppings that protect the horizontal surface of a parapet wall from the weather. Typically they are domed or sloped for water run-off, and overhang the top of the wall by 2” – 3” (50 – 75 mm.) One of the biggest design issues with copings is securing them to the wall in a manner that will resist wind forces.
The issue with wind is not so much horizontal speed as the vertical force or uplift that it can exert on the coping. Air moving over a surface naturally generates lift, but in addition, it will push up and around a building in ways and strengths that can be hard to predict. For example, a neighbouring building could create vortices that generate strong upward forces.
Coping Material and Fixing Methods
Copings can be stone, (natural or pre-cast,) tile or metal. Stone and tile copings can look attractive but are heavy. This increases loads on the wall and adds to construction time and expense.
Aluminium coping offers many advantages over competing materials, such as:
- Lightweight
- Corrosion-resistant
- Extensive range of finishing options
Stone and tile copings are usually held in place with pins and dowels or mortar.
For aluminium copings there are a range of methods. Typically, these entail mounting brackets to the top of the wall, and then fixing the coping to these brackets. However, this can leave screw tops exposed, so many architects prefer Secret Fix copings. These use securing systems that are invisible from both ground level and on the rooftop.
Wind Testing Aluminium 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.
The BRE method is to fix coping to the top of a test wall and attach cables to the coping that connect to a pulling mechanism. The vertical force is progressively increased until the coping comes away from the wall.
This yields an uplift force that’s equivalent to wind uplift pressure. BRE then converts this into a wind speed using the formula P=1/2ρV where P = pressure, ρ is the density of air, and V the wind speed. It should be clear from this that the maximum wind speed a coping can withstand is only inferred from the uplift at failure. In other words, build in a safety margin!
Wind-Tested Aluminium Copings
HJA Secret Fix aluminium copings have been independently tested to 144 mph. That makes them strong enough to stand up to the strongest winds likely in all weather conditions in the UK.
To learn more about aluminium coping or other aluminium rainwater products, call or email HJA Fabrications today.
