In Genesis, Noah’s Ark was covered inside and outside with pitch.
Genesis 6:14 tells Noah to make the Ark from wood and to cover it with pitch within and without. Pitch is a waterproofing substance, commonly associated with bitumen or tar-like materials, that could seal a wooden structure against water.
The exact identity of the Hebrew term translated “pitch” is discussed by translators, but the practical function in the story is clear: the coating makes the vessel watertight. The instruction applies to both the interior and exterior surfaces.
This detail is distinct from the Ark’s timber. Genesis names the waterproofing material separately from the wood used for construction, so answers such as “wood” do not identify what covered the vessel.