An exterior mural is attached to a wall before it belongs to an image.
The substrate expands, contracts, cracks, holds moisture, sheds old coatings, and receives repairs. Paint preparation determines whether the finished work is bonded to sound material or to the next layer likely to fail.
After installation, ultraviolet light alters color. Rain finds edges and openings. Freeze-thaw movement works beneath the surface. Vines, fixtures, signs, exhaust, sprinklers, snow, and building maintenance can affect the painting without making any aesthetic decision.
The artist controls materials and application for a limited interval. The owner controls later wall work. The public sees fading or damage without necessarily knowing which layer failed. A maintenance agreement can clarify inspection, cleaning, touch-up, documentation, and what happens when repair of the building requires alteration of the art.
This custody matters because a mural appears public and permanent while often remaining legally tied to one property and physically tied to one wall. Community affection cannot stop water entering masonry. Ownership cannot make the image socially private.
Weather is not an enemy added after completion. It is one of the mural’s materials, acting slowly and without regard for the original palette.