Q: Is it a requirement for the validity of Jumuah that it be in a masjid and not an ordinary Musallaa? If so, what is the proof for it?
A: If you look at the conditions for the validity of Jumu’ah Salaah in all Schools of Fiqh, you will not find any mention of a Masjid as a condition for Jumu’ah Salaah. According to all math-habs Jumu’ah is valid even in an open field or the Eid musalla. However, since it was a standard practice of the Messenger of Allah (Sallallaahu Alayhi wa Sallam) to offer his Jumu’ah only in the Masjid, unlike the Eid Salaah which he regularly offered at the Eidgah, we will say the Masjid is Sunnah Mu'akkadah for Jumu’ah. Hence it will be sinful to make Jumu’ah in a place other than the Masjid on a regular basis for this is contrary to Sunnah. Once in a while it will be permissible to do so.
Mufti Siraj Desai