628 - תרכח דיני סוכה שתחת סוכה ובו ט' סעיפים

Laws of a Sukkah Under Another Sukkah

1. A sukkah built on top of another sukkah, where the roofing (s'chach) of the lower sukkah serves as the floor of the upper sukkah:

If there are ten handbreadths between the lower s'chach and the upper s'chach—which is the minimum valid height for a sukkah, as will be explained in siman 673—and it is possible to use the upper sukkah with cushions and blankets without them falling into the lower sukkah, then the upper sukkah is valid and the lower one is invalid.

This is because it says, "In sukkos you shall dwell," with the word "sukkos" written without a second vav, implying one sukkah and not a sukkah beneath two roofs.

However, if it is not possible to use the upper sukkah with cushions and blankets even with difficulty, since the upper sukkah is not fit for use at all, not even as a temporary dwelling, it is not called a sukkah at all and does not invalidate the lower sukkah due to the rule of a sukkah under a sukkah.

Similarly, if the upper sukkah is not ten handbreadths high, or if its sunlight exceeds its shade, it is not called a sukkah at all to invalidate the lower one.

2. Therefore, if the lower sukkah has more shade than sunlight even without the shade of the upper s'chach, it is valid in every case, even if the upper s'chach is more than twenty cubits above the floor of the lower sukkah.

Even though the upper s'chach is invalid for the lower sukkah because it is above twenty cubits, and thus invalid s'chach is shading the lower sukkah—

It has already been explained in siman 726 that any invalid s'chach invalidates valid s'chach beneath it.

Nevertheless, the lower sukkah is valid, even if the upper s'chach provides more shade than sunlight.

This is because invalid s'chach only invalidates valid s'chach beneath it when its invalidity is due to its own nature, such as being attached to the ground or being something that can become impure.

But s'chach that is valid in itself, but is invalidated by some external factor—such as being placed above twenty cubits—does not invalidate valid s'chach beneath it, since it is itself fit for use as s'chach for the sukkah below.

3. However, if the lower sukkah does not have more shade than sunlight except by combining the shade of the upper s'chach, and the upper s'chach is more than twenty cubits above the floor of the lower sukkah, the lower sukkah is invalid.

This is because invalid s'chach does not combine with valid s'chach to complete the required amount.

4. One who makes his sukkah on top of a wagon or on a ship:

If it cannot withstand an ordinary land wind, it is invalid.

And even if one sits in it at a time when there is no wind at all, he does not fulfill his obligation, since it is not considered a dwelling at all.

But if it can withstand an ordinary land wind, even if it cannot withstand an ordinary sea wind, it is valid.

And even if one sits in it while the ship is moving, he fulfills his obligation.

For a sukkah does not need to be a permanent dwelling (fit for many days), but rather a temporary dwelling.

5. One who makes his sukkah on top of a camel or on top of a tree, where the top of the tree is the floor of the sukkah, and he made walls there and placed s'chach on top of them, it is valid.

But one may not ascend to it on Shabbos or Yom Tov, since it is forbidden to use animals or things attached to the ground on Shabbos and Yom Tov, as explained in siman 336.

And even a rabbinic prohibition is not set aside for the sake of fulfilling the mitzvah of sukkah, for the reason explained in siman 626. See there.

6. Even if the sukkah is on the ground, but the s'chach reeds are supported by the tree, it is forbidden to enter it on Shabbos or Yom Tov.

This is a decree lest one use the s'chach by placing his belongings there or hanging something from it, and thus end up using the sides of the tree. That is, the s'chach supported by the tree is called the sides of the tree, and it is forbidden to use it on Shabbos or Yom Tov, as explained in siman 336.

7. When does this apply? In earlier times, when it was common to use the s'chach to place or hang their belongings.

But now that it is not customary to do so, we are not concerned about this.

Therefore, it is permitted to enter it on Shabbos or Yom Tov.

Nevertheless, ideally, one should not support the s'chach on the tree, for s'chach should only be supported by something fit to be used as s'chach, as will be explained in siman 729. See there for the reason.

8. If the ends of the s'chach reeds are supported on top of the camel, even after the fact it is invalid,

because it is not stable, since the camel will eventually move and the s'chach will fall.

They only permitted a sukkah on top of a camel if the s'chach is placed on walls that are on the camel, so that the sukkah moves together with the camel.

9. If part of the floor and part of the walls of the sukkah are on top of a tree, and part of its floor and part of its walls are on something else, and s'chach is placed on top of the walls:

If it is constructed in such a way that if the tree were removed, it would still stand on the other support and not fall, it is permitted to ascend to it on Shabbos or Yom Tov using a ladder, as long as one does not use the tree itself.

If not, one may not ascend to it on Shabbos or Yom Tov,

because since it relies on the tree, when one enters it he is using the sides of the tree, as explained above.