In Australia, roofing materials usually fall into one of two possibilities: concrete roof tiles; or corrugated metal roofing with a bonded paint finish (known in Australia as Colorbond, or CB). Which option is best for your situation? Both will keep the weather out, so weigh up the factors below before you decide.
A Bit of History: The concept of bonding paint to a galvanized base originated in Chicago, and was further developed in Australia into a product that has remarkable corrosion resistance and is aesthetically interesting: Colorbond©. It comes in many standard colours and is resistant to the elements. Whereas a galvanized corrugated roof might last 20 years, a Colorbond roof would have a 50 year life or longer.
Terra cotta tiles are also an option; they literally last forever. Think archaeological dig. There are examples of terracotta roofing that have been around for 1000s of years. However it is about double the price of a concrete tile roof.
For our purposes, we will compare concrete roof tiles and Colorbond roofing, and will focus on Melbourne conditions. Both products do an admirable job at what they’re designed for (keeping the weather out). Concrete roof tiles have been used in Melbourne for at least 75 years and there are many houses in older suburbs such as Heidelberg and Camberwell that still have their original concrete tile roofs.
Why would you select one product over another? It comes down to personal taste, lifestyle, a few other factors… and COST.
Architectural Merit: This is a personal matter. Colorbond has a modern stylish look with clean lines. However, there are many concrete roof tile profiles that give a different architectural result than a standard half-pipe tile. For a small addition in price, you could (for instance) select a flat shingle style. There are also many colours in concrete roof tiles.
Noise: This is an important consideration. Insulation and ceiling notwithstanding, you will hear rain on a Colorbond roof. While we might think of raindrops falling on a metal roof as a pleasant sound, it can be disturbing to some people, especially in heavy downpours. Tile roofs are much quieter.
Water Collection: If you want to collect roof water in a tank for household use, Colorbond is the best option. You will harvest more water because concrete tiles have a level of absorbency. Also they tend to retain dirt, dust and so forth which washes into the water tank. During the recent 10 year drought in Melbourne, home owners were encouraged to collect rain water for household use. This influenced the demand for Colorbond roofing.
Weight: Colorbond is a fraction of the weight of a concrete tile roof (10% to be precise!) So your roof framing can be much lighter. Also, a Colorbond roof is no heavier wet than dry. A concrete tile roof will absorb water before it runs off, so a wet tile roof is heavier and engineering specifications need to allow for this.
Rodents: It is simpler to make a Colorbond roof pest-proof by nature of the way the product is installed.
Bushfire: Melbourne is a city adversely affected by summer bushfires. If you are building in the outlying fire-prone areas, BAL (Bushfire Attack Level) regulations will make it in your interest to choose a Colorbond roof, as they are easier to seal against external ember attack.
Resilience: If you need people to climb on your roof for maintenance reasons, Colorbond is more resilient. However, if you need to penetrate the roof (for instance for a vent or air conditioning) this will be more expensive with CB.
Eaves or Veranda. If you have extensive verandas or eaves, a Colorbond roof will be more desirable because of its lighter weight. With verandas you want a shallower roof pitch, and this can only be achieved by some form of sheet roofing. Typically roof tiles are not recommended on a roof pitch of less than 20 degrees. And because Colorbond is a descendant of old-fashioned corrugated steel, this delivers the traditional Australian veranda look.
Cost: Concrete tiles are over 20% cheaper than Colorbond, which is why more than 90% of homes built in Melbourne have a concrete tile roof. The advertising might have you think that CB is as cheap as tiles, but this is not the case. Designers sometimes prefer Colorbond. One client paid to have plans drawn up by a designer. When seeking quotes, they were horrified to see thousands of dollars extra for a Colorbond roof, when they actually preferred a traditional tile roof.
Which roof is best for you? Look at each factor as it relates to your situation. Weigh up its degree of importance, and then decide which roofing material best serves your particular needs, tastes, lifestyle, and budget.