Most self storage units are made with concrete floors because they are easy to clean and they are not easily damaged when heavy or sharp things are moved in and out of the unit. It is not always the case, but concrete can weep moisture from the ground below it and that moisture could cause mold or mildew to form on stored items. To protect the belongings that are placed in a storage unit, the customer can either get wooden pallets that will raise everything off of the concrete floor and help ventilate it or they can put a special water barrier plastic sheeting down to cover the concrete.

The wooden pallets can be purchased from lumber yards and sometimes they can be made to specific measurements to fit the customer's needs. If they are used in a storage unit, it is important to be sure that there is a way to easily get them there since they do not fit in the trunk of a car. To keep the cardboard boxes from tipping into the holes between the pallet slats, a piece of thin plywood or sturdy cardboard can be placed on top of the pallet to cover the holes.

The water barrier plastic sheeting can also be purchased. It is usually sold at most home improvement stores or companies that sell and install various types of flooring such as vinyl or carpet. It comes in large rolls, but can usually be purchased in sections cut from the roll and either rolled or folded for easy transportation.