MSC Floor and Roof Panels may also be Pre Cast in a Nearby Plant. MSC floors and roofs can be engineered from light-gauge steel joists. The joists are attached to an outside wall, then span to an inside wall or column. Plywood forming, placed and blocked from the bottom side, provides the deck to pour, in place, 2 1/2″ of concrete over a reinforcing mesh. The concrete and joists combine to form a composite section through the use of MSC proprietary shear connectors.