How Counter Flashing Works With Base Flashing
Where your roof butts against a wall, chimney, or dormer, waterproofing is handled by two pieces working together. The base flashing (often step flashing) sits on the roof deck and turns up against the vertical surface. The counter flashing is the second layer that caps it from above, with its top edge tucked into a cut groove in masonry (a reglet) or laid under the wall's siding.
This overlap matters because of gravity and capillary action. The counter flashing sheds water down and over the top of the base flashing, so moisture is always directed onto the roof surface and never gets a path to seep behind the metal and into the structure.
Why Counter Flashing Matters in the Inland Northwest
Spokane and North Idaho roofs face conditions that punish weak flashing details. Here is why counter flashing earns its keep locally:
- Ice dams: When snow melts and refreezes at the eaves and along walls, water can back up under shingles. A properly lapped counter flashing keeps that pressurized meltwater from finding the seam behind the base flashing.
- Freeze-thaw cycling: Our repeated freeze and thaw swings expand and contract metal and mortar. Counter flashing set into a sealed reglet stays put far better than surface-caulked flashing that cracks loose over winter.
- Wind-driven snow and rain: Gusts push moisture upward against chimneys and sidewalls. The overlapping design resists that uphill driving force.
Signs Your Counter Flashing Is Failing
Counter flashing problems are a leading cause of chimney and sidewall leaks, and they often show up before the roof itself wears out. Watch for these warning signs:
- Rust streaks, lifted edges, or gaps where the flashing meets the chimney or wall.
- Dried, cracked, or missing caulk and mortar at the reglet line.
- Water stains on interior ceilings or walls near a chimney, skylight, or where a lower roof meets a taller wall.
If you spot these, it is worth a professional look. Sometimes the counter flashing can be reset or replaced on its own; in other cases it is addressed as part of a full roof replacement.
Counter Flashing and a Watertight Roof System
Flashing is only as good as its installation. As a GAF Master Elite contractor, DG Contracting LLC treats counter flashing as part of a complete, integrated roof system rather than an afterthought sealed with a bead of caulk. Done correctly, counter flashing is embedded into masonry or under siding so it relies on physics, not just adhesive, to stay watertight through years of Inland Northwest weather.
If you have a chimney leak or are unsure whether your flashing is doing its job, we offer a free estimate and stand behind our work with a 15-25 year workmanship warranty.