Particle board and plywood are composed of pieces of wood products that have been pressed and glued together. Although they are popular siding materials for storage units, they are not most people's first choice in regions where it rains a lot. For if water does work its way into these products (a possibility enhanced by their composite nature), then you're lost.
Remember that these structures are not merely for storing things away. In addition to their usefulness, the appearance of garden bike sheds storage affects the overall appearance of the property on which they are installed. As such, the unit you choose should be of a design that complements your home. Select one with a rustic design (for instance, board and batten) for a country-style house. If your house's style is more formal, select an garden bike sheds storage with formal features to match (for instance, if your house has an arched window, carry the theme over to your outbuilding).