Mold on Siding, Mold is a type of fungus that thrives in damp, shaded, and humid environments. On residential siding, it typically appears as:

• Black, brown, or dark green patches or streaks that may look fuzzy or slimy.
• Irregular growth patterns, often concentrated in areas with poor sunlight exposure.
• A musty or mildew-like odor, especially in severe cases.
• Possible damage to the siding material, particularly on wood, where mold can contribute to rot.

Algae on Siding, Algae are simple, plant-like organisms that flourish in moist conditions, particularly in areas with high humidity. On siding, algae usually appear as:

• Green, yellow, or brown streaks or stains, often forming a thin film.
• A powdery, slimy, or velvety texture that can spread across large areas.
• Commonly found on north-facing or shaded walls, where sunlight is limited and moisture lingers.
• Not as damaging as mold but can contribute to staining and discoloration of siding materials over time.

Both mold and algae are commonly seen on vinyl, wood, and stucco siding and are typically caused by excess moisture, poor ventilation, and lack of sunlight. Regular cleaning, proper drainage, and sunlight exposure can help prevent their growth.