Metal Roofing in Miami,
seamed by hand,
engineered for the storm.

Different Types of Roof Flashing

A metal roof relies on several distinct flashing types, each shaped for a different vulnerable spot on the roofline. Valley flashing sits in the V-shaped channel where two roof planes meet, one of the most exposed areas on any roof and a common leak point if the metal isn’t formed and lapped correctly. Drip edge runs along the eaves and rakes to direct water off the roof edge and into the gutter instead of behind the fascia. Step flashing and counter-flashing wrap chimneys and sidewalls, layered piece by piece so each course sheds water onto the one below it. Parapet flashing is its own category, built to cap and seal the low walls that rise above the roofline on many low-slope and commercial sections, where standing water and wind uplift put extra stress on the seams.

Penetration flashing, the boots and collars around vent pipes, skylights, and roof-mounted equipment, has to move with a metal panel’s thermal expansion without loosening. On a metal roof, all of these pieces are typically cut and bent from the same coil stock as the panels, so a Galvalume roof gets Galvalume flashing and a copper roof gets flashing that will develop the same copper patina as the field panels over time. That consistency in metal type matters more here than on other roofing systems, since mismatched metals at a flashing joint can drive galvanic corrosion. Homeowners comparing this level of flashing detail against a sloped alternative often look at our tile roof page, or at roof shingles if they want a lower-cost sloped option, before deciding which system’s flashing needs fit their home.

Roof-to-Wall Flashing

Roof-to-wall flashing is the metal strip installed where a metal roof plane meets a vertical wall, such as a dormer, a second-story addition, or a parapet on a low-slope section. Its job is to bridge the gap between two different surfaces so wind-driven rain cannot work its way in behind the siding or up under the panels. On a metal roof this detail carries more weight than it does on shingles, because metal panels expand and contract with temperature swings, and the flashing has to accommodate that movement while staying sealed at the wall line.

There are two pieces working together at this joint. Step flashing (or continuous flashing on longer straight runs) sits under the wall covering and laps over the top of each panel course, while a counter-flashing or reglet cut into the wall material overlaps the step flashing from above. This layered, overlapping approach keeps water moving down and out even during heavy, sideways rain, which matters in a market like South Florida. The flashing itself is typically cut from the same substrate as the roof system, whether that’s Galvalume, aluminum, or copper, so it expands at a similar rate to the panels and doesn’t telegraph a different weathering pattern over time.

Walls aren’t the only place a metal roof needs this kind of transition detail. Valleys, where two roof planes meet, and parapets on flat sections both call for their own flashing approach, and getting any one of these wrong is a common source of leaks that has nothing to do with the panels themselves. If you’re comparing how metal handles these junctions against other systems, our epdm roofing page covers how flat roofs handle parapets and wall transitions differently.

Why is my standing seam roof leaking?

Most leaks on a standing seam roof do not come from the panels themselves. The flat metal field sheds water well for decades, so when water gets in, the cause is almost always at a seam, fastener, or transition point that was not detailed correctly. Common culprits include panel clips or exposed fasteners that were over-driven or under-driven, seams that were not fully engaged during installation, and flashing around penetrations like vent stacks, skylights, or HVAC curbs that was cut short or sealed instead of properly lapped. Roof-to-wall transitions, valleys, and chimney counterflashing are the other frequent trouble spots, since these areas depend on correctly layered metal rather than sealant to stay watertight over time.

Panel damage can also be a factor. A dent from hail or foot traffic that deforms a seam edge, or a scratch through the factory finish that lets corrosion start at the substrate, can eventually open a path for water. On coastal homes, salt exposure accelerates any weak point in the coating or at a cut edge, which is one reason substrate choice matters when a system goes in. Age plays a role too. A roof nearing the end of its service life is more likely to have accumulated small failures at multiple points rather than one obvious hole.

Because the leak’s actual entry point is often several feet from where water shows up on the ceiling, tracking it down usually takes a hands-on inspection of the seams, flashing, and penetrations rather than a guess from the ground. If you are also weighing a full replacement, it helps to compare substrate options, including how aluminum and Galvalume systems hold up differently against corrosion over the long run.

Likely leak source	Why it happens
Fastener backout or over-drive	Loosens the seal at panel attachment points
Incomplete seam engagement	Leaves a gap where water can wick in during wind-driven rain
Poor flashing at penetrations	Sealant alone fails faster than properly lapped metal
Valley or wall transition detailing	Water concentrates at these joints and finds any shortcut
Dents, scratches, or coating breaks	Expose bare substrate to moisture and corrosion

What fasteners do I need for a metal roof

Metal roofs need fasteners engineered for metal, not the roofing nails used on a shingle deck. The standard is a corrosion-resistant screw with a bonded rubber washer that compresses against the panel to seal each penetration. Getting this wrong is one of the most common causes of leaks on an otherwise sound metal system, so the fastener matters as much as the panel itself.

Which fastener you use depends on the panel profile and substrate. Exposed-fastener panels are screwed directly through the flat of the panel into the deck or purlins, so every screw location is a potential leak point and the rubber washer has to stay flexible for years. Concealed-fastener (standing seam) panels use clips hidden under the seam, so fasteners never penetrate the panel face at all, which is a major reason standing seam tends to outlast exposed-fastener systems. The fastener metal also has to match the panel metal, or close to it, to avoid galvanic corrosion where the two touch. A steel screw on a copper patina panel, for example, is the wrong pairing.

Substrate affects fastener choice too. Galvalume panels, with their steel core and aluminum-zinc-silicon coating, pair well with coated steel fasteners rated for that chemistry, while aluminum panels generally call for stainless or aluminum fasteners to avoid reacting with the panel. Panel thickness matters as well: a thicker 24-gauge panel holds a screw more securely over time than a thinner 26-gauge panel, since the threads have more material to bite into.

If you’re still comparing metal against other systems before deciding on fastener details, our tile roof and roof shingles pages cover how those materials attach differently, and our epdm roofing page covers membrane attachment on flat sections.