Is Your Building at risk of Sun Cancer?

Is Your Building at risk of Sun Cancer?

UV Degradation can significantly shorten the life and integrity of your roof.

Auckland has just sweltered through another long hot summer, and everyone is checking their mole-maps. But you shouldn’t just be thinking about yourself…

Have you taken enough precautions to protect your building from the life-shortening effects of that hot summer sun?

Rather than mitigate the effects of solar radiation, most roofs actually contribute to global warming through a phenomenon call the “heat island effect”. This occurs where warming structures heat the air around them thereby raising the ambient temperature.

We’ll look at Heat Islands in another article, but for now lets look at how UV degradation can cause our roofs to age prematurely, leading to sometimes catastrophic failures well ahead of their time.

To illustrate, let me take you back 30 years or so, to when I was working on a gantry on a school roof and I kicked off a wood planer by accident. The aged and brittle roofing panel didn’t even impede its fall. It was only a metre drop, but the plastic shattered and the planer clattered through to the floor some 4m further down. The school, reflecting on the state of the roof, decided a complete reroofing was in order.

Degradation usually occurs when the sunlight provides sufficient energy to chemically alter the bonds in the polymers. While the speed of degradation depends on the materials, additives, and impurities, it’s pretty safe for us to generalize that as the amount of sunlight increases, the rate of degradation increases too.

Different materials have different rates of degradation over time.

·      Ceramic tiles are kiln fired, and hence are the least susceptible to solar damage. They do however have other serious non-solar drawbacks, including weight and brittleness.

·      Asphalt takes decades or centuries to degrade, but it can occur as the oils melt out and evaporate or wash away, leading to an effect known as “alligatoring”. This can be overcome using granulated mix in the surface of the bitumen membrane. Also, to put this in perspective, check out the Kate Sheppard Building where we recently replaced an asphalt waterproofing membrane which was still working fine after almost 100 years.

·      Polyester is a commonly used polymer, as it is inexpensive and can be used to form hard scratch-resistant coatings.  But Polyester does tend to “chalk” over time, which is surface-level degradation, but it does dull the finish.

·      Longer chain polymers like polyvinylidene fluoride (PVDF) are more UV-resistant, and are woven into membranes to increase their physical strength. It’s so robust that the same material you put on your roof is also used in sailboat sails.

Any responsible builder or architect these days is looking to mitigate the heat sink and degradation caused by the sun.

Of course, there’s other environmental factors affecting the degradation of your roof. Rain, wind, dust and debris all play a part in the design and loading calculations, as does varying thermal conductivity of adjoining materials. But with such intense sunlight in NZ, coupled with ozone depletion, and a thinner atmosphere (since we’re nearer to the pole), arguably the main cause of incremental damage to NZ roofs is attributable to UV radiation.

So what you need is a robust, long-life UV-absorbing outer protective skin, to prevent the UV rays being absorbed by the underlying layers.

If you have a specific project criteria in mind, or just want to say “see you later alligator”, give us a call before you specify. We’ve got not only years of experience waterproofing and insulating roofs in some of the most unforgiving environments in NZ, but also several of the most technologically advanced solutions available in NZ, including:

·      Bitumastic Aluminium Coating (BAC) best known for it’s efficacy and value for money

·      Barozzi Thermo-gum – developed using nanotechnology, offers not only exceptional waterproofing and insulation, but is easier to keep clean.

·      Pazkar InoPaz – an Australian government-approved coating for surfaces where drinking water is collected.

We have a wealth of ideas and inspiration which we’d love to share with you, so feel free to give us a call or email any time. Check us out at