Answer
Islam prohibited private seclusion between non mahram man and a woman and the private seclusion is defined as a place where both are there and a locked door prevents others from walking in and out of the room freely. Prophet Muhammad (peace be upon him) said “no man secludes himself with a non mahram woman without her mahram.

Mahram is defined as a non marriageable male relative to the woman i.e. father, uncle, brother etc… and when the woman is in seclusion with her mahram, this seclusion is not considered prohibited. Based on this understanding if a man and a woman live together in one place where no one else can freely enter then it is considered as a prohibited seclusion and they are not permitted to live alone together.

Question
It is popular in non Muslim countries for the couple to have sexual relationships without marriage. Is it permissible for a man and a woman to have premarital sexual relationship?

Answer
Islam has prohibited adultery and limited the sexual relationship to be channeled through marriage. God says, “And do not approach unlawful sexual intercourse. Indeed, it is ever an immorality and is evil as a way.” 17:32

God has described several characteristics for the believers, “And they who guard their private parts

Except from their wives or those their right hands possess, for indeed, they will not be blamed -But whoever seeks beyond that, then those are the transgressors” 23:5-7

Therefore Islam does not permit any sexual relationships between men and women outside wedlock and any other form of sexual relations is prohibited.