What a Fox Valley winter does to brick and flue
A chimney in Elgin endures a punishment that has little to do with how often anyone strikes a match. The masonry stands fully exposed to the broad swing of a northern Illinois year, the muggy heat of a river-valley July, the soaking storms that ride up off the plains, and then the long string of freeze-and-thaw nights that defines a Kane County winter. Brick and mortar are thirsty by nature, drinking in moisture across a wet spell, and once that trapped water turns to ice it swells and shoulders the masonry apart from within. Every hard freeze widens the openings a fraction more, and the crown wash at the very top, the most weather-beaten surface on the whole structure, is usually the first casualty.
The heating season piles on a second and altogether different kind of damage. Each wood fire lays down creosote along the inside of the flue, a sticky, combustible film that thickens in coats and pinches the channel the smoke has to climb. A flue even partly lacquered with hardened creosote is a double problem, a fire waiting for a spark and a draft slowly being strangled, since the very deposit that can ignite is the one choking the airflow the fire relies on. The two forces gnaw at opposite ends of the chimney at the same moment, ice and water chewing down from the crown while creosote climbs up from the firebox, which is exactly why an Elgin chimney wants a scheduled look rather than a panicked one after something has plainly gone wrong.