If you’re getting quotes for a roof replacement in Oregon, flashing is probably not the first thing on your mind. Most homeowners are thinking about shingles, material type, and how long the project will take. Flashing tends to come up as an afterthought, if it comes up at all.
But it is one of the more important decisions in a roof replacement, and it’s one where contractors can differ significantly in what they include and what they leave out. Understanding what flashing does, where it lives, and what Oregon’s climate demands of it will help you ask better questions and make a more informed decision before you sign anything.
What Flashing Is and What It Does
Flashing is the metal material installed at the transitions and penetrations in your roofing system. Anywhere two different surfaces meet, or anywhere something passes through the roof, there is a potential path for water to enter. Flashing is what seals those points.
The most common locations where flashing is installed on a Portland-area home include around the chimney on all four sides, at roof valleys where two roof planes meet and water from both slopes converges, around skylights, around plumbing vent pipes and exhaust vents, along the edges where the roof meets a vertical wall such as a dormer or an addition, and at the eaves where the roof meets the fascia.
Each of those locations is a point where water moves in concentrated amounts. Valleys carry runoff from two planes. Chimney bases collect water on all sides. Vent pipes create penetrations in the waterproofing layer. When flashing fails at any of those points, water finds the path and follows it into the structure below.
Flashing failure is one of the most common sources of roof leaks in Oregon homes. If you have a leak that appears near a chimney, skylight, or ceiling below a valley, there is a reasonable chance the shingles are fine and the flashing is the issue.
Why Oregon’s Climate Is Hard on Flashing
In a dry climate, flashing failure is slower. Occasional rain events and long dry periods between them give sealants time to recover and limit the sustained moisture contact that degrades metal and sealant over time.
Oregon does not work that way. From October through April, the Portland metro area and the surrounding Willamette Valley see sustained rainfall with limited dry periods in between. Flashing at a chimney base or in a roof valley is dealing with concentrated water flow for months at a time, not occasional events.
That sustained exposure degrades sealant faster. It accelerates corrosion on lower-grade metals. It makes small imperfections in the installation, a slightly lifted edge, a hairline gap in the sealant, into active leak points over the course of a wet season.
The freeze-thaw cycles that come with the occasional cold snap make it worse. Water that works its way into a small gap in the flashing seal freezes, expands, and widens that gap. The next rain event finds a larger opening than the one before. Our post on Oregon winter roof damage covers how this cycle develops across a full wet season.
So Do You Replace the Flashing or Reuse It?
This is where homeowners often get different answers from different contractors, and it’s worth understanding why.
There are two schools of thought. Some contractors reuse existing flashing when it appears to be in good condition. Others replace all flashing as a standard part of every roof replacement. The right answer depends on the specific flashing, its age, its material, and its condition, but the default on any quality roof replacement in Oregon’s climate should lean toward replacement rather than reuse.
Here is the reasoning. When you replace a roof, you are resetting the waterproofing system and starting a new service life for the shingles above. If the flashing underneath is 15 or 20 years old and made of a lower-grade material, you are pairing a new 25-year shingle system with flashing that may fail in 5. The new shingles will be fine, but the flashing failure will cause exactly the kind of leak that leads a homeowner to wonder why their new roof is already leaking.
Replacing the flashing during the roof replacement is also the most practical time to do it. The contractor already has the old roofing system stripped off, the deck is exposed, and access to the flashing locations is straightforward. Replacing flashing after the fact, once new shingles are installed, requires removing and resetting shingles around the affected area. It is more disruptive and more labor-intensive than doing it at the time of the roof replacement.
Where Reuse Is Sometimes Reasonable
That said, there are situations where reusing flashing is a defensible decision.
Copper flashing is the most common exception. Copper is extremely durable and has a service life that can outlast multiple roofing systems. A well-installed copper chimney cap or valley flashing from 20 years ago may have decades of service life remaining. Replacing it without cause would be unnecessary.
Recently installed or custom flashing that is only a few years old and was installed correctly can reasonably be reused if it is in sound condition and integrates well with the new roofing system.
Step flashing along a dormer wall or addition, if it is made from quality material and shows no signs of deterioration or failed sealant, can sometimes be left in place when the new shingles are worked around it carefully.
The key in any of these situations is that a qualified contractor should be assessing the condition of the existing flashing and making a case-by-case determination, not making a blanket decision to reuse everything because it saves time.
The Valley Flashing Question Specifically
Valleys deserve their own mention because they are among the highest-risk flashing locations on any Oregon home, and how they are handled varies significantly between contractors.
A roof valley is where two slopes meet and water from both planes funnels together into a single channel. During heavy rain events, valleys carry a high volume of runoff in a concentrated path. The flashing or membrane system in that valley is under sustained load during every significant rain event across a Portland-area winter.
There are two common approaches to valley installation. An open valley uses a visible metal strip down the center of the valley channel. A closed-cut valley uses shingles woven or cut across the valley with a membrane or flashing layer beneath. In Oregon’s climate, we generally see open metal valleys perform more reliably over time because they keep the water moving in a defined channel and make it easier to identify and address any issues that develop.
What matters most, regardless of approach, is what goes underneath. Ice and water shield installed in the valley before any surface material is the baseline for a quality installation in this climate. Our post on why underlayment matters in Oregon covers how the underlayment system works together with the surface material to create a redundant waterproofing layer.
Chimney Flashing: The Most Common Failure Point
If you have a chimney and you’ve ever had a leak, there is a better than average chance the chimney flashing was involved. Chimney flashing is also the most complex to install correctly, which is part of why it fails more often than other locations.
A properly installed chimney flashing system consists of multiple components. Step flashing runs up the sides of the chimney where it meets the roof slope. A saddle or cricket, which is a small peaked diverter, is installed behind the chimney on roofs where the chimney width creates a water collection point. Counter flashing is embedded into the mortar joints of the chimney itself and laps over the step flashing below. All of those components need to integrate correctly, and each one needs to seal against the sustained moisture that Oregon winters deliver.
Reusing chimney flashing on an older home during a roof replacement is one of the riskier decisions a contractor can make. The mortar that holds counter flashing in the chimney joints deteriorates over time. Sealant around the base degrades. If a contractor strips the old roofing system and reinstalls new shingles without addressing the chimney flashing system, any existing weaknesses in that system are being carried forward into the new roof’s service life.
What to Ask Your Contractor
Before you sign a roof replacement quote, it is worth asking specifically what the contractor plans to do with the flashing. A few questions that will tell you a lot:
Will all flashing be replaced, or will some be reused? If some will be reused, which locations and why?
What material will the new flashing be made from? Aluminum and galvanized steel are the most common. Copper is the premium option. The answer gives you a sense of what quality level they are working at.
What is the valley treatment? Is ice and water shield going in the valleys? What is the surface approach, open metal or closed-cut?
What is the chimney flashing approach? Will counter flashing be replaced and reset into the mortar joints, or just sealed at the surface?
A contractor who can answer those questions clearly and specifically is a contractor who has thought about your specific roof rather than applying a standard approach to every job. For more on how to evaluate what a contractor is telling you before signing, see our post on questions to ask before signing with a roofing contractor in Portland.
How We Handle Flashing at Peak Performance Roofing
When we replace a roof, flashing replacement is part of the standard scope of work, not an add-on. Every roof replacement includes new underlayment and ice and water shield in the valleys and at the eaves, new step flashing along all wall transitions, new vent pipe boots, and new counter flashing at chimneys. We assess existing copper flashing on a case-by-case basis and reuse it when it genuinely warrants it.
We do not cut corners on flashing because the consequences show up quickly in Oregon’s climate. A shingle failure on a five-year-old roof is unusual. A flashing failure on a five-year-old roof is not, if the flashing was not done correctly. We would rather do it right once.
We serve Portland, Beaverton, Lake Oswego, Hillsboro, Tigard, Tualatin, Sherwood, Wilsonville, and Oregon City.
You can read what past customers have said on our reviews page and find answers to common questions on our FAQ page.
Schedule Your Free Roofing Quote
If you’re getting ready for a roof replacement and want to understand exactly what is included in the scope of work, we’re happy to walk through it with you. We’ll explain what we find, what we recommend, and why, and put together a detailed quote with no pressure and no obligation.
Schedule your free roofing quote today or call us at 971-979-7325.
Peak Performance Roofing serves Portland, OR and the surrounding metro area. CCB: 231484 | WA: PEAKPPR788NS
