Why do water droplets form underneath the corrugated sheet?
If you put a car in an enclosed space covered with corrugated sheets, but there is no waterproof layer, the heat from the car will rise and condense as it cools. These droplets adhere to the underside of the corrugated sheets and may drop. This might result in brown spots. We strongly recommend installing a waterproof layer (a vapour barrier) when condensation may occur or if the roof is insulated. In this case, always ensure sufficient ventilation.