10 Feb Metal Roofing and Extreme Weather: Wind Resistance
In this series, we’re taking a look at the affects of extreme weather on metal roofing.
Does Metal Really Perform Better Than Other Roofing Products?
Recent devastating hurricanes in our country have brought a lot of press to this subject in recent years. We have all see the video footage of roof damages. Fact is, in these extreme weather events, the roof is a terrible place to be, for all product genres. Does metal really perform better than other products? Let’s take a look at the issues involved.
It’s important to understand that, in a hurricane or other windstorm, there are many things that happen which affect the roof. Of course, you have actual physical windspeed blowing into the roof from some angle. This wind puts strain on the metal panels as it hits them but, sometimes even to a greater degree, it puts uplift pressure on the backside of the roof. Next, you can often have structural movement occurring which will impact roof performance – some homes are built better than others to withstand this. Structural movement can cause roof panels to disengage, particularly if they were not designed to allow for it. Additionally, improper attic venting can cause attics to literally explode. No roof covering will be able to handle that. And, of course, windblown debris striking the roof can compromise its performance as well.
In order to verify their wind resistance, metal roofing products are subjected to uplift tests which simulate actual wind occurrences. This is done through what is called the “bag test”. With some variations, a section of roofing is installed in a laboratory with plastic bagging between the metal and the roof decking. This plastic bagging is then filled with air pressure to determine at what point the metal roof panels disengage. The point of disengagement can be used to approximate a failure point in terms of windspeed.
Some metal products have actual mechanical interlocks between the panels. These products, if properly designed and installed, will often perform better in uplift test than will overlapping panels or panels with a “slip lock” rather than a true interlock. Some products with overlapping panels, though, will have fasteners driven right through the overlap and that can make them perform very well as well.
More questions about wind resistance and metal roofing? We can help. McCarthy Metal Roofing Systems is your local metal roofing specialist in North Carolina.
Next up in this series: Lightning