This question does not get asked nearly enough. And the answer tells you a lot about the quality of the contractor you are working with.
What does roof flashing actually do?
Roof flashing is thin metal, usually aluminum or galvanized steel, installed at every point where your roof meets something else. Walls, chimneys, valleys, skylights, pipes, vent stacks. Anywhere that shingles alone are not enough to keep water out, flashing takes over.
It is one of the most important parts of your roofing system. When flashing fails, water gets into places it was never supposed to be. I have seen more damage from bad or worn-out flashing than from just about any other single cause.
Which types of flashing should be replaced?
Step flashing (where your roof meets a wall) should always be replaced during a full roof replacement. Old step flashing has been through years of thermal cycling and expansion. Reusing it under new shingles is asking for trouble down the road.
Valley flashing should be replaced. Valleys are the highest-flow areas on your roof, where water from two slopes converges and runs downhill. Old valley flashing may be corroded, bent, or improperly lapped. Fresh valley flashing is essential to the new system performing as it should.
Pipe boot flashing absolutely gets replaced. The rubber boots around plumbing pipes and vents crack and deteriorate over time. They will not outlast a new roof system, and reusing them defeats the purpose of doing a full replacement.
Chimney flashing is where it gets more nuanced. If the existing chimney flashing is in good condition and was installed correctly with proper counter flashing set into the mortar, a good roofer might integrate new step flashing around it without tearing everything out. But if the chimney flashing is old, rusted, or showing any signs of failure, it should be replaced completely. This is extra work and adds cost, but it is worth it.
Drip edge should be replaced. Drip edge runs along the eaves and rakes of your roof and is required by current building code. Even if your old roof had drip edge, it should be replaced with new material installed over the fresh underlayment.
"A contractor who reuses all the old flashing can do the job faster and cheaper. That is one reason some estimates come in lower than others."
Why does this matter when comparing estimates?
Flashing replacement takes time, and time costs money. A contractor who reuses all the old flashing can do the job faster and for less. That is one reason some estimates come in lower than others. They are not replacing what they should be replacing.
When you are looking at an estimate, check whether it specifically mentions flashing. Does it say new step flashing? New pipe boots? New drip edge? If the estimate just says "reroof" with no specifics, you do not know what you are getting. And you might find out the hard way when the old flashing fails under your brand new shingles.
What we replace on every full replacement
We replace step flashing, valley flashing, pipe boots, and drip edge on every full replacement. Chimney and skylight flashing gets evaluated case by case, and we talk with you about what we find and what we recommend. Nothing gets reused unless it is truly in solid condition and we are confident it will outlast the new roof.
It is more work than cutting corners. But it means your new roofing system is complete from top to bottom, with no weak links hiding under brand new shingles. That is how we have done it for nearly 40 years, and it is why our replacements hold up.
Have questions about your roof? We offer free roof assessments across Northern Utah. We will take a look, tell you what we see, and give you an honest recommendation. No pressure, no obligation. Schedule online or call (801) 544-5125.
"His team did a great job it took them about 3 days to complete the job. The price was very competitive and he did some extra ice barrier for the edge. Roof passed all city inspection. Bob is local not like some of those other roofers who say they are local but not really."TI Panchev , Google Review