We were repairing a metal roof this week in Marion where I got asked(again) what I think of the agricultural pole barn metal that is becoming popular for residential roofing recently. Also known as R-panel, tin, classic rib, and misquoted as “standing seam.” It’s almost as cheap as shingles, it’s custom cut to the length needed for the job, they have plenty of colors, they are almost sure not to blow off, and you can save on cooling costs. They do have their perks, but they aren’t necessarily going to outlast a good shingle roof. Here are some things to know before installing one:
-First, the obvious, there are hundreds to thousands of penetrations holding your roof on. If the screw doesn’t hit solid wood, it’s going to back out due to expansion and contraction of the house. The metal is even more prone to thermal expansion and contraction. Steel panels can expand approximately one inch in 100 linear feet. All of these screws are fighting against the metal’s natural occurrence.
-Again with the screws. The washers are known to degrade after 15 or more years, allowing water in and rusting the panel where it’s tightened. The screws can also be installed too loose or too tight. This picture is from a 22 year old roof:
-Steel R-panels have foam closure’s, but they are hardly any protection against moisture backup, mostly for pest blockage. The bottom of the roof isn’t as much of a concern, but the valley is definitely at risk. While it works okay, the much preferable “standing seam” metal roof is folded(hemmed) over a sealed cleat near the valley. This creates a hidden fastener sealed valley, and is similar at the eaves.-29 gauge is the common thickness in Southern IL. This will rust through much faster than a 26 or 24 gauge roof, and it’s more prone to being dented.
Some tout this metal as the holy grail of roofing, but it does have it’s downfall’s. We have repaired at least four pole barn roofs on houses in the last year that WILL have a very short life. All of these roofs are less than seven years old. Watch who you buy from and make sure they are aware of the limitations of this roof type. Here are some more pictures of the 22 year old roof, which has already been painted to preserve the finish.