Water Gets In. Ice Pries It Apart. Repeat.
Here's the cycle that destroys more Maryland chimneys than anything else. It starts with a tiny crack or a porous mortar joint — nothing you'd notice from the ground.
Step 1: Rain or melting snow soaks into the crack. Brick and mortar are porous; they drink water.
Step 2: Temperature drops below freezing overnight. The trapped water turns to ice — and ice takes up about 9% more space than water. That expansion pries the crack microscopically wider.
Step 3: Morning thaw. The slightly wider crack now holds slightly more water.
Step 4: Repeat 50 to 100 times per winter. Southern Maryland averages dozens of freeze-thaw cycles every year — we're in the sweet spot where it's cold enough to freeze regularly but warm enough to thaw between freezes, which is actually worse than staying frozen all winter.
What the Damage Looks Like
Early: mortar joints recede and turn sandy. Middle: brick faces start flaking (spalling). Late: bricks crack through, units loosen, the crown disintegrates. By the time it's visible from the ground, the cycle has usually been running for years.
Why the Top of the Chimney Goes First
The exposed stack above the roofline gets the full weather — rain, snow, sun, wind — with no shelter. It also freezes hardest (exposed on all sides) and thaws fastest (full sun). That's why partial rebuilds from the roofline up are so common: the top fails while the sheltered lower masonry is still fine.
Stopping the Cycle
You can't change the weather, but you can deny water entry: a proper crown with drip edge, a cap, sound flashing, intact mortar, and vapor-permeable waterproofing on the masonry. Every one of these is a layer of defense. The chimneys that survive 50+ years in Maryland have all of them; the ones that fail in 20 are missing several.
Send the form — tell us the age of your chimney and what you're seeing, and we'll assess where yours is in the cycle.