Noah and his wife had three sons. The first, Japheth, was born when Noah was 500 years old. All of Noah’s sons were born before the Great Flood, and each was old enough to have a wife before the construction of the ark began. (Genesis 6:18) NIV.
It took approximately 55-75 years to build the ark. Once it was made, they had to gather food. (Genesis 6:21) NIV, All of the animals God sent to Noah had to be loaded into the ark, and Noah and his entire family. (Genesis 7:1-4) NIV.
Noah was 600 years old when the floodwaters came. (Genesis 7:6) NIV.
www.answersingenesis.org