Note whether the stain is on the ceiling near the chimney, on the wall beside it, or in the attic. Where the water lands helps pin down which side of the flashing failed.
Put a bucket or towel under any active drip and move anything nearby that can't get wet. Chimney leaks often run down inside the wall, so check the floor too.
With a flashlight, check the framing around the chimney base for wet wood or water tracks. This confirms it's the flashing and not condensation.
A tube of caulk on the visible seam rarely holds and can hide the real problem. Note what you see and let a roofer inspect the flashing properly.
Chimney flashing is the metal that seals the joint where the brick passes through your roof. It works with a layer of counterflashing tucked into the mortar. Over years of St. Louis heat, freeze-thaw cycles, and driving rain, the metal loosens and the sealant dries out and cracks. Once that seal opens, water follows the chimney straight down into the house.
Older brick chimneys are everywhere in neighborhoods like The Hill, Soulard, and Lafayette Square, and many still have their original flashing. A roofer checks whether the step flashing along the sides is intact, whether the counterflashing is still set in the mortar joints, and whether the mortar itself has crumbled and is letting water in above the flashing. They also look at the shingles just uphill, since a bad valley or cricket can dump water at the chimney.
Call sooner rather than later if the drip shows every time it rains, if the ceiling stain is spreading, or if you smell must near the fireplace. Water that keeps running down the chimney rots the roof deck and framing around it, and that turns a straightforward flashing repair into a bigger structural fix. We handle chimney flashing repairs same day across St. Louis, from Kirkwood and Webster Groves out to Florissant and Ferguson.
Describe what you're seeing to a real St. Louis roofer: call (314) 555-0149 or send the form. Free, no obligation.