Conditional synagogues

Hello,

Ordinarily, the sanctity of a space used for synagogue prayer remains even after that space is no longer used for this purpose, so that the activities forbidden in that space beforehand are still prohibited.

However, if:
a) The synagogue is outside of Israel, and
b) The builders declared it to be a temporary synagogue at the time of the construction,
then after its use is finished, one may use that space for non-prayer activities.

Even then, though, one may not use it for truly non-synagogue activities, like a business or a place to plant.

(Code of Jewish Law Orach Chaim 151:10-11)

Have a great day,
Mordechai