What is the purpose of counter-flashing in chimney flashing?

• A. To deflect water away from the joint and integrate with field shingles.
• B. To prevent water from entering.
• C. To hold nails in place.
• D. To improve color.

Answer: (A)

Counter-flashing around a chimney is designed to shed water away from the seam where the chimney meets the roof and to blend with the surrounding shingles so the roof shed water cleanly. It sits over the base flashing and rises up the chimney, then under the shingles so rainwater is directed down the slope of the roof rather than seeping into the joint. This overlapping, continuous barrier is what keeps water from penetrating at that vulnerable transition, which is exactly why it’s placed light years beyond simply “preventing water from entering.” It’s not about nails or color—the purpose is to manage water flow and maintain a watertight connection between the chimney and the roof.