Daf Yomi - Sukkah 10 - Eating and sleeping in the Sukkah

The Mishna stated previously that if one builds one Sukkah on top of another Sukkah, the upper one is valid and there is a debate regarding the lower Sukkah in a case where the upper Sukkah is not inhabitable. Rav Dimi explains that this debate refers to a case where the lower Sukkah can only support the pillows and cushions in the upper Sukkah with difficulty. Rashi adds that according to the Tanna Kamma of the Mishna, the lower Sukkah will still be valid even if the lower Sukkah cannot support the cushions and pillows of the upper Sukkah and that the lower Sukkah cannot support one who sleeps in the upper Sukkah. Rav Yosef Engel proves from the words of Rashi that for a Sukkah to be deemed valid, it must also be fit for sleeping. This is in accordance with the opinion of the Mordechai who rules that if one can eat comfortably in a Sukkah but it will be uncomfortable to sleep in the Sukkah, he will not discharge his obligation. The reason for this is because a Sukkah must be fit for eating and for sleeping. The Chacham Tzvi disagrees with this ruling and the Chacham Tzvi maintains that a Sukkah is valid as long as there is room for one to eat comfortably. The fact that there is not enough room to sleep does not invalidate the Sukkah. See Avnei Neizer Orach Chaim 479 for further discussion on this matter.