Key Points you need to know
Which Steel?
Big international roofing companies will always buy their steel from quality sources because failure of the steel will have a big impact on their reputation. Steel from smaller
steel mills is cheaper, sometimes half the price, but this steel comes without guarantee. Steel which would be rejected by the big companies is used by other manufacturers who pass all of the risk on to the buyer.
The coating on the steel is also critical. It directly affects the durability and performance of the roof tile. If the steel is not first class quality there will always be problems with these coatings. A corrosion inhibitor coating, such as Alu-Zinc, is critical for the long term performance of the tiles. For example, the best MRT are always coated with a minimum of 150g/sqm of Alu-Zinc (known as AZ150). If, however, the coating is reduced by 1/3 (to 100 g/sqm), the lifespan of the product is reduced by 50%. Sometimes tiles use as little as AZ40, providing only very limited resistance to corrosion. The buyer won't know this for 4 or 5 years, but their roof may begin accelerated corrosion (rusting), while neighbours in the same build environment, can enjoy their roof for 50 years.
The coating on the steel is also critical. It directly affects the durability and performance of the roof tile. If the steel is not first class quality there will always be problems with these coatings. A corrosion inhibitor coating, such as Alu-Zinc, is critical for the long term performance of the tiles. For example, the best MRT are always coated with a minimum of 150g/sqm of Alu-Zinc (known as AZ150). If, however, the coating is reduced by 1/3 (to 100 g/sqm), the lifespan of the product is reduced by 50%. Sometimes tiles use as little as AZ40, providing only very limited resistance to corrosion. The buyer won't know this for 4 or 5 years, but their roof may begin accelerated corrosion (rusting), while neighbours in the same build environment, can enjoy their roof for 50 years.
Stone Coated
Natural Stone is used for all quality MRT. However, different types of rock have different properties. They should not only be hard and strong, but also UV stable to ensure
colours do not change under Ultra-violet exposure. It is also important that the stone has a low iron-content to prevent patches of rust appearing on the tiles and discolouring the roof
Coloured or Ceramic? Where certain colours, such as blue, do not occur naturally, the stone chip can be coated using high quality ceramic technology. There are cheaper ways to colour the chip, but these are highly prone to colour change under UV exposure. The biggest single complaint from buyers of cheaper roof tiles is that of colour fade.
Coloured or Ceramic? Where certain colours, such as blue, do not occur naturally, the stone chip can be coated using high quality ceramic technology. There are cheaper ways to colour the chip, but these are highly prone to colour change under UV exposure. The biggest single complaint from buyers of cheaper roof tiles is that of colour fade.
Bonding Technology
The first stone coated tiles made in New Zealand over 60 years ago used bitumen to bond the stone coatings to the base metal. After long UV exposure, the bitumen began to
crack and ‘chip-loss’ started to occur. Today, the world's biggest companies have developed their own acrylic based coating technology. The Intellectual Property of their
acrylic coatings is a closely guarded secret because it is one of the key differences between products. It’s sometimes said that to make a tile look good when it’s new is easy, the clever technology keeps the tiles looking good for 30, 40, or 50+ years.
There is other technology in the coatings used by the big names in MRT. Not only does this technology keep the chip in place for longer, it can also assist in:
There is other technology in the coatings used by the big names in MRT. Not only does this technology keep the chip in place for longer, it can also assist in:
- Performance against discoloration from organic growth
- Suitability for collection of rainwater
- Protects the stone chips during transportation, cutting and installation
- Protects the coatings during ‘roof-traffic’ (people walking on the roof during installation or maintenance)
Production Technology
To make a lot of MRT to a consistently high and reliable quality, the manufacturing technology has to be first class. The biggest names in MRT invest millions of USD in their tile
press, coating lines and ovens. When a customer looks at a new tile and compares it with a tile from a small supplier, it is difficult to see the difference. This is because the difference
in the technology is inside the product and can’t be seen.
Only after the roof is installed do problems start to occur. The investment in manufacturing technology is what stands behind the manufacturers warranty. The brand name from these manufacturer's provides the buyer with confidence and trust in the future performance of their products.
Only after the roof is installed do problems start to occur. The investment in manufacturing technology is what stands behind the manufacturers warranty. The brand name from these manufacturer's provides the buyer with confidence and trust in the future performance of their products.