How a Cleveland winter goes after a Brooklyn Heights chimney
Sitting on the south side of the metro, Brooklyn Heights does not catch the full lake-effect dump that hammers the snowbelt east of the city, but it catches plenty, and what really wears the chimneys here is the cycling. Cleveland winters swing across the freezing line over and over, a thaw and a refreeze sometimes inside the same day, and that swing is the enemy of masonry. Brick and mortar are porous. They pull in water from melting snow on the crown and wind-driven rain off the valley, and when the temperature drops back through freezing, the water locked inside the masonry expands and shoulders the material apart from the inside out. One winter barely registers. A few decades of them, on housing that was old before most of us were born, turns crisp brick into flaking, spalled faces and mortar joints loose enough to rake out with a screwdriver.
The other half of the problem comes from inside, and from how hard these older homes burn. A long heating season means a lot of fires, and the raw, damp evenings that roll up out of the river valley tempt people into a slow, smoldering, damped-down burn that throws the least heat and lays down the most creosote. Creosote is what wood smoke leaves behind as it cools on the way up a cold flue, and it is both flammable and corrosive. So the two forces work from opposite directions on a Brooklyn Heights chimney. Freeze-thaw chews the masonry from the outside while creosote stacks up on the inside, and a flue that goes a few hard winters without a sweep or a scan is quietly building both problems at once.