Why is 18 unlucky?

It is related to eighteen layers of hell, and the sound of eight words with the same sound as "death bar" is similar to that of "hair", so it has become a symbol of good luck. And 18, which is understood as "hair removal" by everyone, is even more meaningful.

However, it is unlucky to use 18 in houses. I know why many buildings are built on 17 floor or 19 floor. Why not choose 18 layer? I was worried at first, but I didn't know until later. What a surprise.

Do you know the meaning of "18 hell" on the 18 floor? Just build it on the 18 floor ...? Wouldn't it be more ... to buy a house on 18 floor?