14“Make for yourself an ark of gopher wood; you shall make the ark with rooms, and shall cover it inside and out with pitch. 15“This is how you shall make it: the length of the ark three hundred cubits, its breadth fifty cubits, and its height thirty cubits. 16“You shall make a window for the ark, and finish it to a cubit from the top; and set the door of the ark in the side of it; you shall make it with lower, second, and third decks. Genesis 6:14-16 NASB
Pretty good description of how the Ark was to be constructed.
You can quibble all you want but you're arguing with the text. An argument that is against you.
The Bible DID NOT define a cubit in terms that relate to our measuring systems. The Bible specified the dimensions in WHATEVER UNITS Noah used. Do you not understand that the numbers are meaningless TO US unless we have the standard? Noah knew what HIS cubit was, but we don’t.