For nearly maintenance-free storage units, vinyl is the preferred siding. Vinyl lacks the visual appeal of wood, but if you own a house with vinyl siding, why not select a storage unit that is also sided with vinyl? However, vinyl will get dirty over time, making it even less attractive. Mold is often the culprit. Take into account the maintenance required to clean the vinyl periodically.
Comparison of Siding Materials for Storage Units - Natural wood is considered by many the most attractive siding for storage units. But wood exposed over time to water usually rots. Some woods, however, contain natural resins that make them relatively rot-resistant. Cedar is such a wood and very popular as a siding choice for storage units. But even cedar siding is not maintenance-free. Coat cedar with a UV-inhibiting sealer/preservative every other year to protect it from ultraviolet solar radiation. Apply a clear stain, as well, to help preserve its natural beauty.