According to Genesis, Noah's Ark had three decks.
Genesis 6:16 describes the Ark as having lower, second, and third decks. The same passage mentions a window and a door, but it does not provide a modern architectural plan or explain how the interior spaces were divided among people and animals.
The three-level description is part of a larger set of dimensions: the Ark is said to be 300 cubits long, 50 cubits wide, and 30 cubits high. Since the ancient cubit was not perfectly standardized, converting these measurements into metres or feet involves uncertainty.
Modern illustrations often add detailed stalls, ramps, and room layouts that are not specified in Genesis. Those reconstructions are artistic or engineering interpretations. The text itself gives the number of decks plainly: three, arranged as lower, second, and third levels.