A deep dive into Rashi’s Schakh?
Commonly known anything that grows from the ground and is not susceptible to tumah may be used for Schakh (see Sukkah 11a). What though is the function of Schakh, let us try and explore Rashi’s understanding across maseches Sukkah.
The Mishna (9b) teaches that if a Sukkah is under a tree it is like it was built in a house. Both are invalid explains the Gemara, because the verse hints that only one Sukkah is Kosher but not two: excluding three cases: a Sukkah under a Sukkah, a Sukkah under a tree and a Sukkah inside a house.
The Gemara’s explanation arouses a little suspicion, a house and tree are not Schakh how then are they excluded from the verse. Compounded on this is a clarification from Rovo, that if the tree does not provide majority shade, it is not invalid, the question is now strengthened if an invalid cover is problematic and not specifically ‘Schakh’ why then if the Schakh does not provide majority shade is it not a problem, there seems to be no requirement here for Kosher Schakh?
We see a similar phenomenon a bit further on (10a). If one spreads a sheet underneath the Schakh to prevent leaves falling into the Sukkah, the Sukkah is rendered invalid. Reason being explains Rashi (ד״ה ל״ש) is because he has added invalid Schakh to his Sukkah. We can ask a similar question here, in what way is this sheet Schakh if it does not fulfill the Torah requirements of Schakh.
To answer these two questions we can suggest that there are two types of Schakh, generic Schakh and Kosher Schakh. Some covers can fill the requirements of generic Schakh while failing the requirements of Kosher Schakh . A house or tree if they provide majority shade (see Sukkah 2a and further on here) fulfill the basic requirement to be Schakh even though they do not fulfill the requirements to be Kosher Schakh. The sheet also fulfills the requirement to be Schakh but lacks the requirement to be Kosher Schakh. As a result of this, these coverings have the ability to invalidate the Sukkah even though they are not Schakh.
The question that begs though, what is the basic requirement to be considered regular Schakh. Rashi (10a ד״ה ל״ש בא״ד דשויה סכך להגין הלכך מפסיל וכו׳) gives us a working definition: if the covering protects, it is Schakh. [- Rav Wosner quoted later on, bases his definition on the verse וסוכה תהיה לצל יומם מחורב מזרם וממטר - “which shall serve as a sukkah for shade from heat by day and storm and rainfall”, concluding that if it protects from these elements it can be defined as Schakh. It appearsfrom Rashi that these are mere examples of elements to protect from. - It is also interesting to compare our request in Hashkivenu ופרוש עלינו סוכת שלומך - “spread upon us your sukkah of peace” the context implying a protective dwelling.]
Let’s now explore an additional aspect to our definition. The Mishna above that invalidates a Sukkah which has a sheet running underneath it to protect it from the leaves, has an interesting twist. Only if the sheet was placed for the purpose of catching the leaves is it problematic, if it is placed merely to enhance the aesthetic of the Sukkah it presents no problem. Rashi (שם: בא״ד דשויה) explains that its status of Schakh is defined by the intent of its placement, not only does it need to protect but it needs to be placed to protect. (According to this we would need to say that the tree was planted at least partially to provide shade.) [Other Rishonim take an approach of bitul to the Schakh sf.
We see this theme a few pages earlier (8b). If a Sukkah has been built not with the intent of performing Mitvas Sukkah it is a Kosher Sukkah as long as the Schakh was placed to provide shade. This is the same idea as we have seen, Schakh needs to protect to be considered Schakh, if there is more sun it is not protecting. Even when it can protect though, only when it was placed to protect is it valid.
I think though, there is a difficulty with our definition. The first Mishna teaches (2a) (and like we have seen above) if Schakh does not cast majority shade it is invalid, the implication of the Mishna is that there is a critical requirement for the Schakh covering to provide shade no matter what else it protects from. Imagine then a cover that protects from the wind 💨 but fails to provide majority shade, according to our definition it protects and should be considered Schakh, yet the Mishna invalidates it .
To solve the problem perhaps we can suggest that Kosher Schakh has an additional requirement. Schakh the Torah tells us is to commemorate the Sukkos HaShem provided for Bnei Yisrael in the desert. I would like to suggest that those Sukkos (either real Sukkos or clouds of glory) primary function was to shade the people from the sun. Therefore it is not enough for Kosher Schakh to merely shelter from some element rather it needs to specifically shelter from the Sun.
To summarize Schakh’s basic character is to protect. This can be achieved in multiple ways, protecting from falling leaves, the sun or rain. Kosher Schakh on the other hand has a specific requirement to protect from the sun. Both of these types of Schakh need a placement with the intent to fulfill their protective function.
An interesting reflection of the above is discussed in the Teshuvos of Rav Shmuel Wosner (שו״ת שבט הלוי חלק ד׳ סי׳ נז). A certain sage permitted the placing of a plastic covering on top of Schakh the protect it from the rain. The sage argued since it was see through and did not provide shade from the sun it is not treated as Schakh and does not invalidate the Sukkah. Rav Wosner argued though that basic Schakh does not need to protect from the sun to invalidate the Sukkah. Since the covering protects from other elements it is defined as generic Schakh which would invalidate the Sukkah.
The idea of Schakh protecting expresses itself in another Halacha of Sukkah. If one’s soup is getting ruined by the rain one is exempt from the Sukkah and may relocate to his house (28b). The conventional understanding (see תשובות הרשב״א ל״ש סי׳ ע״ח) of the exemption is because he is caused distressed by sitting in the Sukkah he is exempt. Rav Moshe Soloveitchik (from ביאור הגר״א סי׳ תרל״ט ס״ה ד״ה וכ״ז בא״ד ״אין שם סוכה עליו״; recorded in Sefer Harerei Kedem; see also צפנת פענח פ״ו מהלכות סוכה ה״ב) however seemed to have a different understanding. It happened one year that it rained on the first night of Sukkos in the city of Rav Moshe Soloveitchik. Acting in accordance with the Ramo (see סימן תרל״ט ס״ה) that requires one to eat a Kezayis in a Sukkah first night he remained to do this. After finishing his meal inside he remained awake until the rain ceased and then preceded to eat once again in the Sukkah. When asked he explained according to some a Sukkah which is being rained on loses it’s status as Sukkah therefore the first time he ate in it it was not considered ‘eating in a Sukkah’. I recently heard from Rabbi David Goldfein Shlita that the understanding of this opinion is that since the Schakh is currently not protecting to a degree that a person can peacefully live in it, it loses its status as Schakh. Here again we see another aspect of the character of Schakh needing to protect. [Here the nature of the din is a little different, the Schakh does fulfill all the requirements for Kosher Schakh (protects from the sun and was placed for that intent) but since it is currently not functioning as a protection which enables him to sit in the Sukkah it is invalid).
Addendum
All we have discussed has been in accordance with Rashi’s understanding. It can be inferred from Rabbeinu Tam and others (22b ד״ה כאן see also בעל המאור) that they argue on Rashi’s necessity for Schakh to provide shade from the sun. Rashi explains a Gemara in the second chapter that if the Schakh covers half the ceiling and the rest is air the Sukkah is invalid because on the floor there is more sun. Rabbeinu Tam challenges this because in Eiruvin we are taught that if a partision is half covered half empty it is Kosher. Ran supports Rashi by explaining that Schakh is more than a partision and needs to provide shade. Rabbeinu Tam on the other hand understands Schakh as merely another type of partision and therefore compared to the Halacha in Eiruvin that half half is good.
Consistent with his opinion Rabbeinu Tam explains the case of a Sukkah constructed not for the purpose of the Mitzvah of Sukkah with a different condition than Rashi, instead of needing to be made for shade it needs to allow the penetration of rain (see קהילות יעקב סימן א׳). That being said, I do not think Rabbeinu denies the character of Schakh to protect rather he does not understand the additional requirement of Kosher Schakh protecting from the shade. [It may be argued though, according to Rabbeinu Tam there is no source for the idea of intent determine the status of the covering, this fits neatly with Tosfos disregard for Rashi’s distinction between whether the sheet has been placed to protect from the leaves and when it has been placed to be aesthetically pleasing (see Tosfos 10a ד״ה פירס.)
They (Tosfos 10a ד״ה פירס; Mordechai תשלו) therefore take an approach of bitul to understand why if a sheet was placed to beautify the Sukkah it is Kosher. Biur Halacha (סי׳ תרכ״ז ד״ה ואם אינו לנוי) brings both explanations and discuss a practical difference. If one placed clothing on top of the Sukkah to dry, according to Rashi it would not invalidate according to Tosfos and Mordechai it would . He concludes to act stringently.]