Later, a small fire-preventive wall was placed between gabled roofs of adjacent houses so that the wall protruded between the first floor roof and the second floor roof, and this wall became to be called udatsu.
そののち、切妻屋根の隣家との間についた小さい防火壁で、1階屋根と2階屋根の間に張り出すように設けられているものも「うだつ」と呼ぶようになる。