Difference between Mosque and Hussainiyyah
Why it is not permitted to do what can be done in a mosque in hussainiyyah (place of mourning Imam Husayn (‘a), and vice versa? Because if it is permitted we can have one place which can be used both as a mosque and a husainiyyah in order to prevent the wastage of land and costs of building.
There are some limitations for women and sometimes for men for entering mosques; however, there are much fewer limitations for entering hussainiyyahs. Of course one will be granted a much greater reward for performing prayer in the mosque compared to a husainiyyah and this is why both kinds of building are constructed.