What are the five flashing materials?
Aluminum, copper, galvanized steel, lead, and EPDM rubber, and each has a job it is best at.
Aluminum is the most widely used flashing in residential roofing. It is lightweight, easy to shape, and resists corrosion in most environments. Roofers reach for it for step flashing, valleys, and drip edges because it bends cleanly without cracking. One catch: aluminum touching concrete or treated lumber needs a protective coating, or galvanic corrosion will quietly eat it.
Copper is the premium option. It can last the better part of a century or more, and the green patina it develops actually protects the metal underneath. You see it on historic homes and high-end custom builds. The catch is price: copper runs several times the cost of standard materials, so it is a long-term investment rather than a budget pick.
Galvanized steel is the workhorse. Strong, affordable, and good under snow loads and impact. The zinc coating keeps the steel from rusting, but once that coating gets scratched or worn through, rust moves in fast. It is the sensible choice for inland homes where salt air is not a factor.
Lead is the most malleable of the bunch, which makes it the best option for complex or irregular penetrations like old chimney bases. It is less common in modern residential work, but roofers still reach for it when a penetration has a shape nothing else will conform to cleanly.
EPDM rubber earns its keep at pipe boots and other round penetrations where rigid metal will not seal. It is flexible, affordable, and easy to install. Just understand it is a supplemental material, not a substitute for metal flashing at structural joints. Right tool, specific job.
Where does flashing go, and why does placement matter?
The material matters, but so does the location, because each placement puts different demands on the metal and each has its own failure mode. Step flashing fails when the pieces are not overlapped correctly. Valley flashing fails when the profile is too shallow. Drip edge fails when someone installs it under the underlayment at the eaves instead of over it. Small details, big water damage.
- Step flashing: roof-to-wall intersections, like where the roof meets a dormer. Each piece overlaps the one below, working with the shingles to shed water. Needs a malleable metal like aluminum or copper.
- Valley flashing: the V-shaped channel where two slopes meet, which is a high-volume water highway. A W- or V-profile keeps water from jumping sides in heavy rain, a detail that gets skipped in rushed repairs.
- Drip edge: runs along eaves and rakes, moving water off the deck and into the gutters. Code requires it on asphalt shingle roofs; without it, water wicks back under the shingles and rots the fascia.
- Counter flashing: covers the top edge of base flashing at chimneys and masonry, embedded into the mortar joint.
- Kickout flashing: the little piece at the bottom corner where a slope meets a wall. Without it, water runs straight down the siding instead of into the gutter, and the rot that follows is anything but little.
- Pipe boots: EPDM rubber seals around vent pipes because it conforms to the shape and compresses tight.
How do the materials compare on lifespan and cost?
Durability and cost do not always move together. Copper costs the most upfront and lasts the longest, often outliving the shingles around it several times over. Aluminum and galvanized steel are the affordable middle ground, typically good for a few decades, with galvanized needing an occasional check for coating damage. Lead sits in between on cost and lasts a very long time, though health concerns limit where it gets used. EPDM rubber is cheap and does its narrow job well, but expect to replace boots a couple of times over the life of a roof.
Two problems trip up homeowners who never heard of them. First, galvanic corrosion: when two incompatible metals touch, an electrochemical reaction eats through the weaker one. Aluminum and copper should never be in direct contact, and aluminum near treated lumber needs a barrier coating. Second, thermal expansion at chimneys and masonry: as temperatures swing, flashing grows and shrinks. A two-part system solves it, with base flashing attached to the roof deck and counter flashing embedded in the masonry, so the two pieces move independently and the seal survives the seasons.
Which flashing works best for Oregon weather?
For most homes around Damascus, Gresham, and the Portland metro, aluminum and galvanized steel cover the bases: we are inland enough that salt air is not the enemy, but wet enough that installation quality matters more than almost anywhere. If you are near salt air, aluminum or stainless steel is worth the upgrade, because salt can cut galvanized steel's life dramatically even with the coating intact. Copper suits historic and high-end homes, lead handles the weird old chimney bases, and EPDM boots take care of the vent pipes.
One thing worth remembering: flashing does not work in isolation. It has to integrate with underlayment, siding, and ventilation as one system, and Oregon rain will find any spot where it does not. A roofer who treats flashing as an afterthought is setting you up for a roof repair you did not need to have. If a leak has already found its way in, our roof leak guide walks through what to do next.
What I've learned from years of looking at failed flashing
Here is something that surprises most homeowners: flashing is usually the most neglected part of a roof, even though a huge share of the leak calls we get start there. People focus on shingles because shingles are what you can see from the driveway. Flashing hides under shingle edges and behind siding, so it gets skipped.
I have seen roofs less than ten years old with serious water damage, not because the shingles failed, but because the flashing was the wrong material for the spot or was not lapped correctly at a valley. The shingles looked fine. The damage was happening behind the walls.
Flashing failure starts small: quiet seepage for months before you ever see a stain on the ceiling. By the time you notice water inside, the damage behind the wall is usually well established. My honest advice is to have the flashing inspected every two to three years, especially if your home is past 15 years old or you have had roofing work done recently. And when you are getting a new roof, ask your contractor exactly which flashing materials they plan to use and why. A contractor who can answer that clearly is one who knows what they are doing.