Stucco Field Guide
The location and timing of a crack usually name its cause — read the pattern before reaching for a repair.
Inside corners always crack. Two wall planes meet there and move independently, so the plaster at the junction is asked to stretch in two directions at once. A crack that stays under about 1 mm wide is a movement joint in disguise, not a failure.
Cracks that run from the corners of window and door openings follow the same logic. The opening interrupts the wall plane and concentrates movement at its corners, so cracks tend to radiate from those points when the structure shifts.
Map cracking — a fine network of cracks — is read by the calendar. When it appears within the first year, the cause is almost always in the application: a too-dry base that pulled water from the scratch coat, a finish coat applied before the base had cured, or insufficient moist curing overall.
On narrow screens, swipe or scroll the plate sideways.
When map cracking appears years later on a wall that was sound, the cause is usually below the plaster: movement or settlement in the structure. Recoating without addressing that movement only resets the clock on the same cracks.
Efflorescence is a different signal entirely. The white powder is salt carried through the wall by water and dried on the surface, and it means water is getting behind the finish. The repair starts with finding the water path, not with washing the wall.
Loose, hollow-sounding, or flaking areas point to bond failure — and where the finish is being pushed off in flakes, wire embedded too close to the surface is a prime suspect, because rusting wire expands.
Further reading