Understanding the specific failure points of metal roofing can save you thousands in structural repairs.
1. Fastener Failure
The rubber washers on roof screws (neoprene) degrade over time due to UV exposure. When these washers crack or shrink, water can seep directly into the screw hole.
2. Stack Flashing Vulnerabilities
The "boots" around pipes and vents are often made of rubber that expands at a different rate than the metal, eventually breaking the waterproof seal.
3. Seam and Lap Leaks
If the sealant between overlapping panels dries out, capillary action can pull water uphill and under the panels during heavy rain.
4. Improper Curb Flashing
HVAC units and skylights are installed on "curbs" that are difficult to seal against the ribs of a metal panel. If not integrated perfectly, water will pond and leak.
5. Corrosion and Oxidation
Any scratch in the protective coating exposes raw steel. Once rust begins to pit the metal, microscopic holes form that allow water to penetrate.
6. Thermal Movement
Metal roofs expand and contract daily. This constant movement can eventually back screws out or enlarge the fastener holes, creating slow, hidden leaks.
7. Poor Valley Design
Valleys carry the highest volume of water. If the flashing is too narrow or blocked by debris, water will overflow the edges and enter the home structure.