When a roof leaks, most people assume the shingles failed. But in our experience, the shingles are usually fine. The leak almost always starts somewhere else — at the flashing. It’s the least glamorous part of a roof and the one most responsible for keeping your home dry.
What flashing is
Flashing is thin, weatherproof material — usually metal — installed anywhere your roof meets something it can’t simply shingle over. Its job is to bridge those gaps and direct water away from them. Shingles handle the wide-open field of the roof; flashing handles all the tricky transitions where water wants to sneak in.
Where you’ll find it
- Around chimneys — one of the most common leak points on any roof.
- In the valleys — where two roof slopes meet and water flows fastest.
- Where the roof meets a wall — such as around dormers or additions.
- Around skylights, vents, and pipes — every penetration through the roof is a potential entry point.
Why most leaks start here
Flashing is detailed, time-consuming work. Each transition has to be measured, formed, and layered so that water always flows over the top of the next piece, never behind it. There’s no shortcut that holds up over time. When a roof leaks within a few years of being replaced, it’s usually because the flashing was rushed, reused, or sealed with caulk instead of being properly installed.
The shortcut to watch for: reused flashing
Here’s one worth knowing about. On a roof replacement, it’s faster and cheaper to leave the old flashing in place and shingle around it — especially the flashing around a chimney. But old flashing is often corroded, bent, or no longer sealed well, and tucking new shingles against it just hides a future leak. Proper practice on most replacements is to install new flashing, not reuse the old. Relying on a bead of roofing caulk to seal a transition is another red flag: caulk is a finishing touch, not a substitute for correctly formed flashing.
How we approach it
At Trinity Roofing, the flashing details are where we slow down, because they’re where roofs are won or lost. We’d rather take the extra time to form and install flashing correctly than hand you a roof that looks great on day one and leaks by the third winter. If you’re getting quotes, it’s a fair and smart question to ask any roofer: are you installing new flashing, and how? The answer tells you a lot.
Wondering whether your flashing is the problem? Call us at (978) 429-7083 — no pressure, just a straight answer.