Weird Chimney Leak Only Happens During Sideways Rain

Hey everyone,

I’m dealing with one of those frustrating problems that only shows up under specific conditions. On this 1920s bungalow I’m working on, the chimney flashing leaks, but only during heavy wind-driven rain when the precipitation is coming in sideways. During normal rainfall, even heavy downpours, it stays completely dry.

The chimney itself is in good shape - the brick was recently repointed and looks solid. The flashing appears to be installed correctly (lead counter with copper step flashing), but somehow when the wind picks up and the rain starts coming in at an angle, water finds its way in.

A mason who looked at it mentioned that the texture of the older brick might be redirecting water in unexpected ways under these conditions. He proposed grinding a drip edge into the brick, but I’m hesitant to modify the original material on such an old home.

Has anyone encountered this specific issue before? I’m especially curious if any of you who’ve worked on these classic Chicago bungalows have found solutions that preserve the historic integrity while solving the leak.

Thanks in advance for sharing your experience!