Metal Roof Flashing

Metal Roof Flashing Basics

Metal roof flashing, commonly referred to as trim in the metal roofing industry, encompasses all the transitional pieces that seal the edges, ridges, valleys, and wall connections of a metal panel roof. Unlike asphalt shingle roofs where individual flat flashing pieces are woven into shingle courses, metal roof flashing must integrate with continuous panels that have raised ribs, standing seams, or corrugated profiles. Each trim piece is bent to match the specific panel geometry and sealed with closure strips that fill the gaps at the panel ribs. Standard metal roof trim profiles include ridge cap, rake trim, eave drip edge, sidewall trim, endwall (headwall) trim, valley trim, and various transition pieces. These are typically manufactured from the same gauge and coated steel as the panels themselves.

Trim Types and Locations

Ridge cap flashing covers the peak where two opposing roof planes meet. It overlaps both panel edges and uses outside closure strips to seal against the panel ribs. Rake trim covers the gable edge of the roof, wrapping from the panel surface down over the fascia. Eave trim functions as the drip edge, directing water into the gutter. Sidewall trim seals the junction where a metal roof meets a parallel vertical wall, similar to step flashing on a shingle roof but as a continuous piece with a formed profile. Endwall trim covers headwall junctions. Valley trim or valley flashing on metal roofs can be a W-shaped metal trough similar to shingle roof valleys, or a formed piece that integrates with the panel ribs on both converging planes. Each location requires the appropriate inside or outside closure strip for the specific panel profile.

Common Metal Roof Flashing Issues

The most frequent issue with metal roof flashing is missing or deteriorated closure strips. Without closures, every panel rib creates an open gap at the trim that admits wind-driven rain, insects, and debris. Over time, foam closures can compress, shrink, or degrade from UV exposure, reopening these gaps. The second most common problem is insufficient allowance for thermal expansion. Metal panels move significantly with temperature changes, and trim pieces must accommodate this movement with slotted holes or expansion joints. Rigid fastening at every point causes the panels to buckle (oil-can) or pull away from the trim. The third issue is galvanic corrosion when the trim metal is different from the panel metal, such as aluminum trim on steel panels, or when incompatible fasteners are used.

Insurance Claims for Metal Roof Flashing

Metal roof flashing claims most commonly involve wind damage at the exposed edges and transitions where uplift forces are greatest. Ridge cap, rake trim, and eave trim are the most frequently damaged trim pieces during high-wind events. Hail impacts can dent trim and compromise the seal at closure strip locations. When documenting metal roof flashing damage for a claim, note the specific trim type, the panel manufacturer and profile, the material and color, and the linear footage affected. Replacement trim must match the existing panel profile exactly, which may require a custom order from the manufacturer. This lead time and matching requirement should be noted in the estimate. Xactimate pricing for metal roof trim is generally higher than standard flashing line items due to the specialized fabrication.