It is Permissible to Pray in Streets adjacent to the Mosque

Question :

What are the limits of a mosque considered to be in Islamic law, and are the streets adjacent to the mosque regarded as part of the mosque, in which Friday prayer is correct, when the mosque is crowded due to the presence of many people, even though there are other mosques which are not filled with worshippers?

Answer:

The limits of the mosque in which the Muslims pray the five daily prayers in congregation are defined by its surrounding walls, be they of stone, wood, palm branches, cane or the like. This is what is ruled as being the mosque, in which it is forbidden for the menstruating woman, the woman with post-natal bleeding and the person who is in a state of post- sexual impurity and their like to sit. For those who arrive at the mosque finding it crowded with worshippers, it is permissible that they pray the Friday prayer or any other prayer, whether they be obligatory or non-obligatory, in the nearest place to the mosque such as its adjoining streets - so long as he catches the prayer with the Imam, due to the necessity of this on condition that they are not in front of the Imam. But this prayer will not carry the same ruling as that in the mosque. And Allah knows best.

Source:
The Permanent Committee
Fatawa Islamiyah, Vol. 2 Pages 178-179