Changing a prayer room in a house into a toilet
1-3-2011 | IslamWeb
Question:
assslamalakum brother we are going to alter our house after 15years the prayerroom which is been used since 15years is going to change to toilet is it permited in islam to change the prayer room to toilet
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad 
is His slave and Messenger.
In our view, it is permissible to change the room that is allocated for the prayer into what is mentioned in the question because this room does not take the ruling of an endowed mosque in regard to the prohibition of changing it [the mosque] or invalidating the purpose for which it was endowed. Allocating a room for the prayer does not necessarily mean that it has become an endowment. Shaykh Ibn ‘Uthaymeen 
while clarifying that the prayer room at home does not take the ruling of the mosque, said: “The people in the past used to allocate a Musalla (prayer area) for women in their homes, and have a special room for women to pray. However, it is not acceptable or valid to make ‘I’tikaaf in this prayer room, because this room is not a mosque neither in reality nor by decree. It is for this reason that it is not an endowment. So, if the house is sold including this prayer room, the sale is valid, and if someone enters the house and says that he wants to pray in this place because it is a prayer room like the mosque, and that you should not prevent him from the mosques of Allaah; we would say to him that we will prevent him because this is not a mosque. Besides, if a menstruating woman stays in it while she is in menses, then this is permissible for her, and if someone who has no ablution stays in it while he is in a state of sexual impurity, then this is acceptable and if he enters it and sits down without praying two Rak’ahs, this is permissible. Also, it is permissible to buy and sell in it and do any permissible thing that is forbidden to do in the mosque. The same thing applies to the prayer rooms that are in government offices; they do not take the ruling of a mosque. The same thing applies to women’s prayer rooms in girls' schools as they do not take the ruling of the mosque, because they are not mosques neither in reality nor by decree.”
Allaah Knows best.