Create a dated record
Photograph the crack and surrounding area and note doors, floors or finishes that have changed nearby.
Water and movement are separate questions
A crack can admit water without being the primary structural concern, or movement can matter without visible leakage.
Rapid or widespread change deserves qualified assessment
New displacement, multiple related symptoms or visible instability should not be reduced to a cosmetic patch.
Do not hide the evidence too early
Finishing over an unexplained changing crack can make later assessment harder.
Safety boundary. General planning information only. Do not open, dismantle or work on hazardous electrical, gas, structural, fire-protection or contaminated-water systems unless you are appropriately qualified and authorized.