Genesis says Noah coated the Ark with pitch inside and outside.
Genesis 6:14 instructs Noah to make the Ark from gopher wood and to cover it with pitch within and without. Pitch is a dark, sticky, water-resistant substance traditionally made from tar, resin, or related materials. In the narrative, it serves the practical purpose of sealing the vessel against water.
The Hebrew word translated as “pitch” is related to a root associated with covering or atonement, and translations vary in how they render the term. Some use “bitumen” or another tar-like expression. Despite those wording differences, the central idea is a waterproof coating applied on both sides.
This detail is distinct from the Ark’s wood. Gopher wood identifies the stated building material, while pitch describes the protective coating. Genesis also says the vessel had rooms, three decks, a door in its side, and an opening near the top.