Proudly American
Use a fixed view without approaching the stack
From a safe spot, take a wide photo that includes an unchanged nearby wall or opening. Find an older image from roughly the same angle. Record when a gap, loose piece or shift was first noticed and whether roof work or an impact happened nearby. A measuring app on a single oblique image cannot establish stability.
Describe the pattern rather than guessing the cause
Is there a gap where the stack meets the house, a bulge limited to one face, or a crack following joints over several courses? Are pieces landing below? The National Park Service distinguishes leaning, bowing and cracking as separate masonry conditions. A service request can document which is visible while leaving the cause and urgency to the person assessing it.
Route the question to the right professional
Ask whether the observed movement calls for a structural engineer before cosmetic work. Request a written description of areas examined and any access restrictions. If masonry appears in immediate danger of falling into an occupied or public area, move away and contact emergency services from a safe place. Do not push against the stack or climb up to check for movement.