The Mechaber (151:12) discusses which activities may be done in the rooms above the Bais Haknesses. Any degrading activity done on a permanent basis for example sleeping, is prohibited. Sleeping there occasionally by chance is permitted. It is questionable if other activities are permitted. Is the area above the Bais haknesses comparable to the second floor of the Azarah which is not sanctified, or since it is called a Mikdash Mi’at it is like a second floor in the Haichal which has the same kedusha as the Haichal itself?
The Rema says that the halacha of the Mechaber that it is prohibited to sleep above the Bais Haknesses only applies if it was originally built as a Bais Haknesses and now one wants to sleep above it. However, if it was originally built as a house to live in and only afterwards it was designated as a Bais Haknesses it is permissible to sleep above it. The same is true if they were both built at the same time it is permissible to live above the Bais Haknesses since the living quarters above were never sanctified. Still no degrading activities, such as a bathroom should be done there. The Shar Hatziyun explains from the Taz that even though it has no kedusha, still it holds back the teffilos from going up to the Ribbono Shel Olam. Because of this a Bais Haknesses should not be set up underneath the area where these activities take place. Reb Elyashiv zt”l holds even if the bathroom is on the third floor it is still a problem. Other poskim are lenient.
The Mishna Berurah says that it is better not to rely on the psak of the Rema that it is permissible to sleep there if it was originally a house. The Knesses Hagedola says that he himself saw that those who lived above the Bais Haknesses were never successful. Some lost all their money, others died. One should be especially careful not to sleep on top of the place where the Aron Kodesh is.
Therefore Reb Shlomo Zalman zt”l says that one who does live above a Bais Haknesses should make sure that his bedroom is on the other side of the house, not above the Bais Haknesses. The area above the Aron Kodesh should be left empty and not used at all.
The Sharei Teshuva quotes the opinion of the Rambam in Shialos U’tshuvos P’ar Hador who disagrees with the psak of the Mechaber. The Rambam holds all activities are permissible including sleeping. However, directly above the Aron Kodesh which has the Sifrei Torah, no activities at all should be done.1
Prepared by R’ Avrohom Yehoshua Ziskind
1Sources: Mishna Berurah, Dirshu