TT #77 · Parashas Noach · Seventh Aliyah · Passuk 11:3
They said to one another: “Come, let us make bricks and burn them thoroughly.” And the brick served them as stone, and the bitumen served them as mortar.
Torah Temimah notes the technological choice of brick in a stone-less valley.
English: “The brick served them as stone” — in a land without stones they manufactured bricks.
Custom
The builders adapted to the alluvial plain of Shinar by firing bricks in place of natural stone.