Your metal roof is only as strong as the fasteners that hold it in place. Spotting fastener issues early can help avoid major house damage.
Causes of Failure
Fastener failure is a result of installation issues or aging. If fasteners are not driven in correctly, then they will allow water incursion. Every fastener consists of a metal roofing screw combined with a rubber washer. When installed properly, the washer forms a tight seal against leaks. Fasteners that are under-driven won't hold the washer firmly to the roof, thus allowing moisture to seep beneath. Over-driven or off-center screws cause the edges of the fastener to raise up, which also allows water beneath.
Another problem is age, particularly if screws aren't properly galvanized. Over time, rust and corrosion will weaken the screw. Age can also cause the rubber washers to degrade over time, so they eventually may shrink or break free. An additional aging issue is that temperature fluctuations may force screws out of the roof, leading to under-driven screw issues.
Signs of Failure
The most obvious and sometimes the only sign of a fastener problem is a leak in your roof. You may not notice the leak until a wet spot forms on your ceiling. Regular attic inspections, where you look for wet ceiling damage like water stains or mold, as well as inspect insulation for dampness, can help you catch leaks in the early stages.
You can also sometimes visibly catch an issue on the roof exterior. Rusting or corroding screws can stain metal roof panels or stand out simply because they are a different color than the panel. Missing washers are also sometimes visible, even from ground level. It's also a good idea to inspect the roof each spring to make sure winter temperature fluctuations didn't loosen any of the screws.
Screws that were improperly driven need to be aligned properly. Under-driven screws can be tightened, while over-driven screws may require loosening. If the washer is too compressed from over-driving, then it may also need replacement. Off-center screws must be fully removed and then reinserted.
Rusted or otherwise damaged screws and washers require a full replacement. Stains on the roof from rust can sometimes be eradicated with a rust remover, but test it in a hidden area to make sure it doesn't damage the metal roof finish. Once the fastener repairs are done, any water damage in the home must also be repaired.
Contact a roofing contractor in your area if you suspect issues with your metal roof fasteners.