Strength of metal

As we move deeper into the 2012 hurricane season we ought to become more conscious of the reports issued by the Meteorological Department — and each report of any system in the Atlantic Ocean ought in turn to cause us to check our level of hurricane preparedness.

Last week we began our look at protecting our homes by paying attention to any vulnerabilities on our roofs. We paid particular attention to roof shingles, but note that this is not the predominant form of roof covering in Barbados and also that homes which do carry shingles tend to be more expensive properties, which hopefully are covered by insurance.

However, there can be no question that the vast majority of homes in this country are covered by metal sheets, which we tend to refer loosely to as either “galvanise” or “permaclad”. In fact, it would be fair to say that most structures, from the sheep pen in the backyard to some of the largest commercial and industrial buildings have metal roofs. Our concern here though, is the home.

If you have a metal roof on your home, here’s what one set of experts say:

“Metal roofs … are designed to withstand hurricane strength winds and rain. They are the most durable roofing material, able to resist strong winds, hail, extreme heat and fire, and repeated cycles of freezing and thawing. They have a long life expectancy, are virtually maintenance free, and are even recyclable after their long life.”

But concentrating on the sheeting, without paying attention to the overall roof structure could be just as dangerous. All over Barbados, following the passage of Tropical Storm Tomas two years ago, road and fields were littered with roofs that had been removed in whole by the winds. So, in a sense the metal sheets showed clearly their strength, but if the roof is not firmly affixed to the rest of the structure it can be all in vain.

So make sure, particularly if you live in a wooden house, that your roof is secured by hurricane straps — which present a cheap method of retrofitting.

Now let’s return to the metal sheets. The experts have advised that since just about every structure in Barbados is impacted by salt air, the homeowner should pay attention to signs of corrosion. If there is rust, there is some degree of weakness, and if that rust is occurring in the area where the sheet is fastened to the structure, then the degree of vulnerability increases. Remember also to check your fasteners, whether they are the old “galvanise” nail or the screws use in more recent installations.

Again it is important to remember that if the wind is able to lift one sheet, then the probability of further damage occurring increases significantly.

Here’s another piece of advice from the experts:

“There is no standard fastening system for metal roofs due to the wide variety of options. Practically all metal panels feature overlapping seams for strength and water protection. Double locking seams provide the highest level of both.

“The key to getting a wind resistant metal roof installation is to ensure that the lowest panel fasteners are installed close to the roof eave and that the manufacturer’s recommended spacing for fasteners is followed carefully. Many of the past failures in metal roofs have been in the panels covering hips and ridges. Newer metal ridge caps have screws along the bottom edge to improve strength.”

So while you have the time, talk a walk on your roof and look for weaknesses. If you still are not sure what to look for, get a carpenter to take the walk with you.

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