The Chazon Ish stated [re: a man shaking a woman’s hand who is not his spouse, his mother, his daughter, or his granddaughter] [p.p. 130-131])
A Yeshiva student from England refused to shake hands with his step-mother when greeting her. His father was extremely upset with his refusal. He demanded his son display “derech eretz” towards his step-mother and shake her hand. The son refused stating he was taught it was impermissable with a non close blood relative. This affected the fathers relationship with the son. Some family members told the son to give in al sholom bayis. The son asked a shaila from the Chazon Ish. The Chazon Ish responded with a short and sharp answer – “Chok V’lo Yaavor, Issur Gamur” (It is a prohibition that one dare not violate; It is absolutely forbidden,) Violating this halacha was out of the question despite sholom bayis and kibud av. (Oz Vehadar, p. 494).