How do you choose what kind of roofing iron will best suit your house?
Choosing the wrong profile (the way the roofing iron has been shaped) for your home can potentially cause you problems with leaks and also lower the kerbside appeal, which could devalue your home.
If you are roofing a brand new house, then remember that salesmen have a bias towards their own products and builders generally like to choose whatever is easiest. Sometimes the development of the estate has rules about types of roofing and cladding materials, so this could also limit you in your choice of roofing profile. However, if you can choose anything you like and want an unbiased viewpoint, talk to your builder and also a roofer who has experience in your type of dwelling.
If you are re-roofing an existing home, the choices are possibly greater than if you have a new house, because your suburb is likely to have changed dramatically since its inception. In the past, materials were sometimes used for convenience and what was popular at the time, such as Decramastic tiles or asbestos. Since there were lots of issues with both of these products, it is unlikely that you would want to re-roof your house with the same materials.
The profile you select could be influenced by lots of things:
• How close you are to the sea
• How close you are to any type of industry that causes corrosive pollution
• If your home is surrounded by trees that drop their leaves or branches
• The pitch of your roof
• The spacing of your battens and rafters
• Likelihood of cyclones or extreme weather
• How much of the roof can be seen from the road or garden?
• The age and style of the house you own
The last two points are the ones that are mostly concerned with what is sometimes called ‘kerbside appeal’ rather than anything practical about how well the roof will work for your home. Some roofing profiles look better on some types of homes, which can make your neighbours happier with you and make it easier to sell the house.
For instance, many people who have a Queenslander-style home choose corrugated iron because it curves so nicely into bull-nosed verandas. They also often choose from the colour scheme that was popular when the home was built. This is likely to be the classic silver, deep red or bottle green with matching guttering.
If you have a modern suburban brick home, then it can be jazzed up with bright gutters around a roof of virtually any colour or profile that you feel suits the colour of the brick, the surrounding garden, the roofs around the house, or anything else you would like to take into consideration.
People living on bigger blocks often have large trees and select colour schemes that make the house blend in with these so that they look as if they are part of the landscape, while others want their home to stand out, and so choose something from the bright and beautiful colour ranges available today.
Proximity to the sea
While steel is incredibly durable, rust reduces the strength of the metal, making the roof more likely to leak or to be damaged in strong winds. As a general rule, roofing sheets will not rust if the protective coating on the sheet remains in place, but once the coating is compromised, corrosion begins.
If you live close enough to the sea so that you can see white caps from anywhere in your yard, then your roof is at greater risk of rusting due to the constant sea spray, than if you lived further inland. This is because under ordinary circumstances, you need three things to make rust: metal, oxygen and a liquid like water. Sea salt is made from a whole bunch of minerals (mostly sodium and chloride) and some of them are corrosive when placed on metals. Sodium chloride has another property that is not at all helpful when corrosion is considered: - it is very good at absorbing water. If you have lots of salt sitting on your roof every day of the year, it is going to encourage the rusting process.
Along with high moisture content, high temperatures generally speed up chemical reactions so if you live in a humid tropical climate, your roof is more likely to rust than if you live in a cold desert.
Australian manufacturers of roofing iron recommend that if you live within 100 metres of the surf, then you should use stainless steel because this metal roof profile is the least likely to rust. You just have to look at an old kitchen sink that has been filled with hot water and chemicals year in, year out, to see that this is true. The kitchen sink will still shine up beautifully when polished.
If you live between 100 and 200 metres of a surf beach, then a roofing profile, such as “Ultra Steel” is recommended. This is more protective from corrosion than standard roofing sheets, but because the home is further away from the salt spray, stainless steel is not needed.
Like salt spray, air-borne pollution from industries can also corrode metal, leading to rust, a weakening of the material and an increased likelihood of leaks. Therefore, manufacturers of roofing iron recommend the same kinds of profiles be used as those recommended when people live beside the surf: if your dwelling is within 100 metres of a factory pumping out pollution, then stainless steel will give you the most protection, and if you live within 100 – 200 metres of the factory, Ultra Steel (or something similar) is recommended.
Branches and leaves that sit on your roof
Over-hanging branches may give a poetic, romantic or even a scary, daunting look to a house, but this can be a look you wished you didn’t have after the repeated rubbing damages the surface of your metal roof, promoting the growth of rust.
In addition to branches rubbing on the surface of your roof, most trees drop leaves, which will attract moisture and perhaps create an acidic environment as they decay. This humid, acidity acts on the coating of the roof, promoting rust.
Similarly, a television aerial, weather vane, or other items that are incorrectly installed and repeatedly rub against your roof will gradually remove the roof coating, encouraging the rusting process.
Please note: Copper or water coming out of a copper pipe (such as from the overflow on a hot water system) should never be allowed to come in contact with a standard metal roof because water containing copper is highly corrosive.
If your roof has a low pitch (less than 5o), then it is prudent to select from the profiles that have a high ridge in the metal. These are usually called “square line” even though they don’t actually have any squares on them, but instead ridges run the length of the sheet, like ordinary corrugated iron. Examples of square line roofing materials include Topspan, Monoclad or Trimdek. The reason that the corrugated profiles are usually not suitable on a flat roof is because they may not be able to carry the volume of water during heavy rain, and this could cause the building to be flooded.
If your roof pitch is above 5o, then virtually any roofing profile will work and the primary decision will be based on what you want to pay and which one is the most appealing.
If your roof has a steep pitch (more than 25o) then it is likely that it will be on display for the whole street to look at for a long time, so carefully choose the colour. Until around the 1970s, almost everyone had a silver, red or green roof because you had to either leave it the way it was installed, or paint it. Once you started painting it, you had to keep doing this for the rest of its life to keep it looking good. Today, we are lucky to be able to choose from a wide range of coloured roofing sheets that are pre-painted, such as the Colorbond range. There are two basic types of colours available: those that stand out and really make a statement and those that blend into most Australian environments.
A steep-pitched roof can be covered in any profile that takes your fancy but the most commonly used is corrugated. This is probably because it is the most traditional roofing profile available, having been used since around 1830. Corrugated roof sheeting is comparatively light but very strong, and it helps direct water flow right into your guttering. The size of the corrugation can vary from the narrow and small corrugation to a much deeper and wider version.
Batten and rafter spacing
The spacing of your battens and rafters probably depends on the location of your house, and the roofing materials originally chosen when the house was built. For example:
• If you live in a region that is prone to cyclonic winds, then the house frame has to be a lot stronger than if you live in a climate that usually has mild winds. The battens and rafters will be therefore closer together in the cyclonic region.
• If you were thinking of replacing your tiled roof with an iron roof the rafters would be strong enough because tiles are very heavy and so the rafter spacing has to be closer to bear the weight. However, the battens used to place tiles on are smaller than those used for metal roofing, and so they would need to be replaced with something that suits the Australian Building Standards.
Cyclones and other severe weather conditions
Since its invention almost 100 years ago, corrugated sheet metal has proved to be a winner around the world, especially in areas that are prone to disasters because, as previously mentioned, it is relatively light weight and strong. Other advantages are that it won’t burn and it can be recycled over and over again. If it blows off your roof in a cyclone, someone else can use it to make a fence, or it can be melted down and recreated.
Because of its extreme weather, Australia took to corrugated iron in a big way, and it is still very popular in areas that are prone to hail and high winds, making it a likely consideration for most people if they live in South East Queensland.
Other roof items to consider
• Skylights – most people use skylights to let light into hallways or other parts of the home that are not well-lit, as they avoid the need to have an electric light on during the day.
• Windows in the roof – these are often found in roofs with a steep pitch. Because they let light in and hot air out, they can save you in power, as well as making an attractive feature in the roof.
• Solar panels – by using the overhead sun to generate electricity, thousands of households in Brisbane are saving money and helping to reduce emissions.
• Wind ventilators: Devices that cool buildings, such as the “Whirly Bird”, have been used for decades to cool homes, offices and factories, saving power and creating a more pleasant environment. Whirly birds are mechanically spun by the breeze or hot air rising, creating a vacuum and sucking the hot air out of the ceiling or upper part of the room, thus cooling the rest of the building.
Today, with the advent and increased use of solar power, there are more options available. For instance, a “Solar Star” is a solar-powered fan that appears to suck air more vigorously out of the roof space than a whirly bird, but presumably only works while power goes to it, rather than 24 hours a day like the whirly bird. The writer of this article has been unable to find independent tests to see which one is more effective.
Other things also cool the home, such as foil that is placed directly under the roof to reflect heat, and also batts that are placed on the ceiling in the roof cavity.
Lastly, to help you choose the best type of roofing material, talk to people who are involved in the industry. Find someone experienced who does roofing in your area because they not only know the local by-laws that govern your region, as well as the freaks of weather that can hit, but they live there. For instance, if you live on the coast near Moreton Bay or inland near Ipswich, then talking to someone who is involved in roofing, Brisbane in particular, will help you to find out not only what is recommended for your zone, but what they, their clients and their friends have found are the best types of insulation etc. for the local population.