Sukkah 10A

היכי דמי? כגון שהתחתונה צלתה מרובה מחמתה, ועליונה חמתה מרובה מצלתה, וקיימי תרוייהו בתוך עשרים.

What are the circumstances? It is in a case where in the lower sukka, its shade is greater than its sunlight, rendering the sukka fit, and in the upper sukka, its sunlight is greater than its shade and it is therefore insignificant, and the roofing of both is within 20 cubits of the ground.

ופעמים שהעליונה כשרה ותחתונה פסולה היכי דמי? כגון דתרוייהו צלתן מרובה מחמתן, וקיימא עליונה בתוך עשרים.

And there are times when the upper sukka is fit and the lower sukka is unfit. What are the circumstances? It is in a case where in both sukkot their shade is greater than their sunlight, and the roofing of the upper sukka is within 20 cubits of the roofing of the lower one. In this case the upper sukka is fit, while the lower sukka is a sukka beneath a sukka and is unfit.

פשיטא! תחתונה כשרה ועליונה פסולה איצטריכא ליה. מהו דתימא: ניגזר דילמא מצטרף סכך פסול בהדי סכך כשר, קא משמע לן.

The Talmud asks: This is obvious. There is nothing novel in any of these scenarios. The Talmud answers: It was necessary for the tanna to mention the case where the lower sukka is fit and the upper sukka is unfit, as it contains a novel element. Lest you say: Let us issue a decree and deem the lower sukka unfit, as perhaps the unfit roofing of the upper sukka joins together with the fit roofing of the lower sukka and renders it unfit as well; therefore, the tanna teaches us that the two roofings do not join together and the upper roofing does not render the lower sukka unfit.

כמה יהא בין סוכה לסוכה. ותהא תחתונה פסולה?

The Talmud elucidates this halakha. How much space should there be between the roofing of the upper sukka and the roofing of the lower sukka for the lower sukka to be considered a discrete entity and therefore disqualified as a sukka beneath a sukka?