Originally, udatsu were built as a wall to prevent a fire spreading to adjacent houses when a row of machiya (a traditional form of townhouse found mainly in Kyoto) houses were built with little space between adjacent houses.
本来、町屋が隣り合い連続して建てられている場合に、隣家からの火事が燃え移るのを防ぐための防火壁として造られたものだった。