What salt air and a hard freeze do to a Perth Amboy chimney
A chimney in Perth Amboy weathers a combination that few inland stacks ever face. The salt-laden air that drifts in off the Arthur Kill and the Raritan Bay settles into the brick and the mortar joints and works on them year-round, drawing moisture in and leaving behind the salts that crystallize and push the masonry apart from the inside. On the older homes near the waterfront this shows up as the white, powdery efflorescence streaking down the brick and as mortar that you can rake out with a fingernail. That slow chemical wear softens a chimney long before any single freeze finishes the job.
Then winter arrives and the freeze-thaw cycle takes over. Water that the salt air has already drawn into the brick freezes, expands, and pries the masonry apart a little more with every cold snap, and a New Jersey winter delivers dozens of them. The face of the brick spalls off in flakes, the crown at the top cracks and stops shedding water, and the mortar crumbles until the joints no longer hold. A chimney that looked solid in October can have a split crown and a dozen open joints by April, and every one of those is a path for water to reach the flue and the framing. This is why we are so insistent on looking at the crown and the upper masonry before the cold sets in, while there is still time to seal and rebuild before water and ice get a winter to work.