Dirt and grease stains are the most common stains found on exterior stucco. The primary cause of these stains is being too close in proximity to other objects, or rain. For example, a driveway may be too close to the stucco, resulting in grease stains from vehicles being transferred to the stucco. In the case of dirt stains, trees, bushes or gardens may be the culprits. This is especially prevalent if a sprinkler is located near the exterior wall, driving dirt and water onto it and causing stains. Dirt and grease can easily be tracked onto stucco if it is close the ground, and rain can cause dirt and grease to splash up onto the exterior surface.

Rust stains are also common on exterior stucco. They may be caused by rust emanating from nearby metal objects, such as vent covers or grates. If the exterior stucco is synthetic and composed of layers of foam board with a stucco coating, the studs used to secure the boards may be rusting underneath, leading to rust stains on the surface of the wall. If the stucco is not synthetic, underlying wires may still be rusting and causing surface stains.

Chimneys made of stucco often develop soot stains. These stains will look black and greasy, and can be difficult to remove, requiring specialized cleansers. Grills can also cause soot stains on stucco if they are in close proximity to the wall.