Decks and slabs can be specified as behaving as either One-way or Two-way. Even on the same layout, some areas can be One-way and some areas Two-way. Examples of One-way decks are composite decks, noncomposite roof decks, steel grating, and concrete slabs on pan joist or beam-and-column floor systems. Examples of Two-way decks are flat slab and flat plate systems, with or without drop caps.

In some aspects the modeling requirements differ between the two. Because of the specialized nature of the One-way analysis, the modeling requirements for One-way decks are generally more stringent, as described below. In many cases the modeling commands are tailored to these requirements.

Two-way decks should never be assigned to areas of steel framing. The analysis of Two-way decks is performed in RAM Frame for the purpose of calculating the gravity loads on the Frame members, and in RAM Concrete; it is not performed in RAM Steel. Hence any loads on Two-way decks would not get distributed to steel framing. Only One-way decks should be assigned to steel framing.