What Causes a Metal Roof to Start Leaking?

Failed Seams

• Most modern metal roofs are joined by interlocking or soldered seams, and older metal roofs may also have similar connections between the panels. Either method is prone to failure from age, faulty installation, storm damage or foot-traffic during installation. Seams can also fail if the house settled unevenly, causing stress along the joints. Achieving durable, solid seams is one of the many reasons why metal roofs are best installed by a professional, and seam repair requires the same expert attention.

Fastener Holes

• Metal screws that fasten a metal roof to the underlayment are inserted through the metal, and each fastener is a potential leak source. Professional installers use great care not to over-tighten fasteners, which can cause the roof to pucker, but some bending of the metal is possible. Rust around any screw is a good indicator of a leak, but water can still seep through without rusting the metal. If the roof is dry, clear silicone can seal the screw holes until a permanent repair is possible; however, silicone can also seal water under the roof and cause more damage.

Rust-Through

• New metal roofs can last up to 100 years, and the same is true for older roofs. However, old metal roofs require conscientious maintenance to resist rust. If your roof has areas of heavy rust, the panels can weaken and eventually degrade to allow water through rust holes. In cases of extreme rust-through that create a roof leak, the corroded material is cut out and patched with new metal or the whole panel is replaced.

Gutters

• Gutters are designed to carry water away from the roof, but poorly-installed or neglected gutters can cause more harm than good. Fasteners and flashing must be installed securely, and gutters must be cleaned regularly. Leaves or ice blocking gutters can cause water to back up and flow under the roof, eventually leaking into your home through the underlayment.

False Leak

• Occasionally, what appears to be a roof leak is not a leak at all. Water under the house or improper insulation can create condensation, which wicks up to the rafters. Left unattended, condensation can accumulate, leaving wet areas inside the attic. If your roof shows no signs of disrepair, condensation could be the problem. A sump pump under the house can remove standing water, and a contractor can evaluate your insulation to determine whether you have a proper vapor barrier to prevent condensation problems.