What is the ruling on building restrooms and toilets for women on the upper floor above a portion of the men's prayer hall, as part of the mosque's expansion?

The roof of a mosque and what is above it are part of it. It is not permissible to build upon it except for the benefit of the mosque, such as expanding it for prayer. Toilets should not be built above the mosque, out of reverence for its sanctity, for mosques were built for the remembrance of Allah and prayer, and it is not befitting to place toilets above those praying.