Where Flashing Goes on Your Roof
Shingles shed water across open slopes, but they cannot seal the spots where the roof changes direction or where something pokes through it. That is the job of flashing. You will find it in several key places:
- Valleys — where two roof planes meet and concentrate runoff.
- Chimneys and skylights — wrapped with step and counter-flashing.
- Pipe and vent penetrations — sealed with boots or collars.
- Walls and dormers — where the roof meets vertical siding.
- Eaves and rakes — drip edge flashing guides water into the gutter.
Each of these transitions is a potential leak point, and flashing is the metal that makes the connection watertight.
Why Flashing Matters in the Inland Northwest
Around Spokane, Colbert, and North Idaho, flashing takes a harder beating than it does in milder climates. Heavy winter snow piles up in valleys and against chimneys, and repeated freeze-thaw cycles work water into any gap that flashing fails to seal. When meltwater refreezes at the eaves, ice dams can back water uphill underneath the shingles — at that point your flashing and underlayment are the last line of defense.
High wind can also lift or loosen poorly fastened flashing, and hail can dent or split older metal. Because so much of our region's weather damage shows up at these transitions, properly installed flashing is one of the single most important details on an Inland Northwest roof.
Common Flashing Problems We See
Flashing rarely fails because of the metal itself — it fails because of how it was installed or how it has aged. The most common issues include:
- Reliance on caulk or roofing tar instead of properly layered metal, which dries out and cracks in a few winters.
- Rusted or corroded flashing on older roofs that has worn thin.
- Reused flashing left in place during a reroof rather than replaced.
- Lifted or loose flashing after wind events or settling.
- Failed pipe boots, where the rubber collar cracks from UV and freeze-thaw exposure.
If you notice ceiling stains near a chimney, skylight, or interior wall, the flashing is one of the first things worth inspecting.
Flashing and Your Roof Replacement
Because flashing is integrated with the shingles and underlayment, the best time to address it is during a full roof replacement. Quality flashing should be made of durable metal, correctly layered so water always sheds over the top of the next piece, and fastened in a way that allows for the expansion and contraction our temperature swings cause.
As a GAF Master Elite contractor, DG Contracting installs new, code-compliant flashing as part of every reroof and backs the workmanship with a 25-year warranty. If you are unsure whether your flashing is doing its job, request a free estimate and we will take a look.