There are several benefits to having a metal shed as opposed to a wooden one, the main benefit being that a metal shed requires significantly less maintenance. The disadvantage of a metal shed is that they tend to build up large amounts of condensation. But just a few simple steps will help you keep condensation from becoming a major problem for your metal shed.
Build a damp-proof course into the base of your metal shed. This will prevent moisture from rising, which in turn will prevent condensation from forming.
Construct the base of your metal shed so that it's a few inches larger than the base rail, and make sure the foundation contains a damp-proof membrane. This membrane needs to be approximately 2 inches higher than the area around the shed.
Allow plenty of time for the foundation to cure once the concrete is laid. This could be anywhere from three to seven days, or longer, depending on the moisture level in the air. Erecting your shed too soon will cause the water drying from the concrete to form as condensation inside your shed.
Apply sealant to the base rails on the inside of your metal shed after the shed has been bolted to the base. Apply a silicone or mastic sealant to prevent water from seeping into the shed and causing condensation.
Insulate your metal shed. Start by cleaning off the inside of the roof with a methylated spirit. Dry off the roof panels, and attach polystyrene tiles using special spray glue. Make sure the glue bonds polystyrene to metal and is not affected by temperature.