A brown ring stain on the ceiling near your chimney is most often failed flashing at the roof joint rather than a problem with the chimney itself. Properly repaired, it stays fixed. Patched with tar, it comes back within a season or two.
What flashing is supposed to do
Flashing is the metal that seals the joint where the chimney passes through the roof, and correct flashing is two separate layers working together.
Step flashing is a series of individual L-shaped pieces woven between each course of shingles up the sides of the chimney, so water running down the roof is carried over the shingle below rather than behind it. Counter flashing is a second layer whose top edge is let into a groove cut into the mortar joint, then folded down over the step flashing. Water running down the brick face hits the counter flashing and is directed out onto the roof.
Both layers are necessary. Step flashing alone leaves the top edge exposed; counter flashing alone has nothing to overlap.
Why tar is not a repair
What we find on Plainfield roofs, repeatedly, is a bead of roofing tar smeared along the brick-to-shingle joint. Tar expands and contracts at a different rate than both the metal and the masonry it is bridging, so it cracks within a season or two of Illinois temperature swings.
Once cracked, it is worse than nothing. Water enters through the crack and is then held against the joint by the tar itself, unable to drain or dry. If a contractor quotes you a chimney leak repair consisting of caulk and tar, you are buying next year’s leak.
The cricket nobody mentions
On any chimney wider than roughly 30 inches, water and snow running down the roof pond against the up-slope face. The remedy is a cricket, a small peaked saddle built behind the chimney that splits water around both sides.
Missing crickets are why so many wide chimneys in this area rot the roof decking behind them. Plainfield’s relatively open, flat terrain leaves roofs more exposed to driven rain than the wooded river neighbourhoods to the north, which makes it a more frequent issue here. When we re-flash, we assess whether a cricket is required and build one rather than leaving a known failure point.
Talk to a local chimney pro
If you have a stain, damp drywall in an upstairs closet, or rusty streaks on the brick, get it looked at before the freeze. Water in masonry expands about nine percent when it freezes, and Illinois delivers that cycle dozens of times a winter. We cover Plainfield and the surrounding Will County area.
Written by Josh Amber, co-owner of Ember Chimney Sweepers, Oswego IL. Published September 23, 2026.