What is the ruling on a woman using a shared bathroom due to the unavailability of a separate bathroom?

If the communal bath refers to a bath used by more than one family in a single location, or by members of one family (men and women), then there is no harm for a woman to enter it out of necessity and in the absence of an alternative. She must, however, guard against forbidden acts and strive to find a separate bath.

As for the public bath designated for washing, entering it without an excuse is disliked and may even be forbidden. It is permissible with an excuse, but forbidden if it leads to a forbidden act according to Islamic law, due to the Prophet's (peace be upon him) prohibition of men entering baths except with loincloths, and his prevention of women from entering except out of necessity, and his warning to any woman who takes off her clothes outside her husband's home.