Busting the Myths of Metal Roofs 3

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Wednesday, October 7th, 2015
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With metal roofing comes many preconceived notions and concerns, from causing increased noise to creating stuffy, over hot internal environments. But which are true and what are the pros and cons?

  1. The Rain Is Louder

Myth: Today, metal shingles are fastened onto an existing wood roof deck. To be affected by a downpour and make a sound, the roof would have to comprise sheets of metal over open rafters allowing the metal to reverberate. A skylight would actually be noisier than a metal roof.

  1. They Stop Ice From Forming

Myth: When snow melts over a warm roof, whatever the material, it runs to the cold eave edge and refreezes to form ice. To avoid this, attic ventilation needs to be increased, heat sources removed and insulation upgraded to R-50 to stop the heat going to the roof.

  1. They Shed Snow

Part myth: Temperatures need to rise from between five and eight degrees above freezing for this to occur. In addition, in heavy snow areas, the ribs of standing seam metal roofs direct snows to valleys and can become compacted and cause damage to the roof. A valley on a roof is the most common element that needs replacement every 30 or 40 years. It catches the water where there is a change in angle.

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  1. They Makes Homes Warmer

Part myth: Not all metal roofs are the same, and some can actually significantly reduce the amount of heat entering the home. Aluminium can be particularly energy efficient, reducing heat levels by as much as 34 per cent. In addition, there are also various energy saving coatings, including HI-R pigments that can further reduce heat gain, delivering a cooler building in the summer but keeping it warm in the winter.

  1. They Don’t Add Value

Part myth: A report by Remodeling Magazine recommends installing a new roof as one of the seven best investments prior to selling. However, an upscale new roof using standing-seam metal can be quite costly, demanding a $37,481 price tag on average, and only paying back 54.5 per cent of its cost at resale, according to the report.

On the flip side, the lifespan of the roof and reduced maintenance requirements could also appeal to a potential buyer and this is first in our list of advantages.

Advantages

Longevity

Depending on the material, metal roofs can have a life expectancy between 40 and 70 years. Traditional asphalt roofing materials only last around 12 to 20 years before issues may occur.

Durability

Depending on the metal you choose, metal roofs can withstand wind gusts of up to 225 kilometres per hour, will not corrode or crack, and may be impact-resistant. They are also less likely to require periodic costly maintenance; although they still need to be inspected.

Energy efficiency

As mentioned above, some metal roofs can actually reflect solar radiant heat and reduce cooling costs on an average of 10 to 25 per cent (and as much as 34 per cent.)

Environmentally friendly

Between 25 and 95 per cent of a metal roof can be recycled content, depending on the material used. They are also 100 per cent recyclable at the end of their life as a roof. Most shingle tear-off waste ends up as part of the building-related waste stream, estimated globally at 40 billion dollars per year.

Aesthetic Versatility

Metals are capable of achieving challenging and complex architectural designs. Other more traditional roofing options, like single-ply systems, tend to be rigid by comparison and made vulnerable by bending. Metal panels, on the other hand, are malleable enough to fold back on themselves to create various angles while maintaining structural integrity.

metal roof

Performance

Metal’s performance life is most comparable to a modified Built-Up Roof (BUR) assembly. A typical metal roof is conservatively half the weight of modified roof, while vastly exceeding the strongest modified BUR by a factor of 50 to one.

Speed and ease of installation

Due to its capacity for complex design, more intricate detailing means more time and more demanding installation requirements. However, the lighter weight of metal solutions make them perfect for retrofits. Unlike non-metal systems, metal retrofits can eliminate tear-off of the underlying roof, significantly reducing time and cost associated with tear-off and removal.

Disadvantages

Affordability

Metal roofs can be up to three times more expensive than other roofing materials. Although longevity and durability are legitimate benefits noted above, investing in a metal roof only makes sense if you are in it for the longer term to enjoy the cost benefits.

Expansion and contraction

If the metal roof solution comprises large panels, these can expand and contract. If they are not properly installed with fasteners that allow the metal to ‘breathe,’ they are prone to loosening.

Colour Inconsistency

It is very hard to match existing materials when repairs are required or the building is extended or expanded.

Performance and Durability

Despite appearing in the advantages section, there are potential performance and durability drawbacks depending on material specification and/or installation. Water accumulation anywhere on the roof can eventually cause serious damage. Low-grade metals may also be thinner and less durable. Some metals rust in certain climates or dent more easily during hailstorms or installation.

There are also some applications where metal is ill-suited:

  • Metal roofs typically require a slope of ¼:12 or more to ensure watertight protection
  • The structural integrity of seams and other components can be damaged on roofs with heavy traffic, while scratches to the finish coat may make the roof vulnerable to corrosion
  • The high level of craftsmanship required in detailing and sealing areas around penetrations means roofs with numerous penetrations or rooftop equipment are not a good option for metals
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3
  1. Tim Perry

    An enlightening discussion, thank you very much.

    I must say, I traditionally have associated metal roofing with a more industrialised setting and therefore a stuffy and either extremely hot or extremely cold environment.

    It certainly sounds as though the rain would be louder on a metal roof. Interesting to hear that this is not the case.

  2. David Chandler

    Justin, you have not dealt with roof warranties.
    Clients should be careful not to take a roof warranty at face value. They may not be what the client thought they were getting. Assuming a 15 year warranty is required a builder will probably hand a roof warranty over with others at practical completion – normally from one of the well branded manufacturers. On the face of it, that's fine until the client has a problem or reads the fine print. Most will have a caveat to the effect that if the roof was not installed in accordance with the manufacturer's specifications then the warranty will be void. In Victoria a licensed roof plumber will be required to self certify that the roof has been installed in accordance with the contract, the relevant codes and in accordance with the manufacturer's recommendations. This is not always a reliable process. Over 30% of roofs I inspected for BER school buildings were not installed correctly. Some were not designed correctly and some had substitute materials such as cheap pop rivets which were rusting only months later. On a number of occasions the builder had not inspected the work and accepted the certification. These roofs ain't roofs?