Genesis 6 contains the instructions for building Noah’s Ark.
In Genesis 6, God tells Noah to build the Ark and provides its principal dimensions: 300 cubits long, 50 cubits wide, and 30 cubits high. The chapter also describes compartments, a covering, a side door, and three decks.
Genesis 7 then moves into the Flood’s immediate events, including Noah’s entry into the Ark, the animals, and the onset of the waters. Genesis 8 covers the recession of the Flood and the birds Noah sends out, while Genesis 9 records the covenant and rainbow sign.
Knowing the chapter division helps distinguish the preparation instructions from the later chronology. The Ark narrative spans Genesis 6 through 9, but the construction command itself is located in chapter 6.