Directives Regarding the Walls of the Sukkah
Question: How many walls should a sukkah have?
Discussion: According to the basic halachah, once a sukkah has two proper walls standing perpendicularly, the third wall may be a mere tefach.54 However, utilizing this law involves many complex particulars which require a high level of halachic expertise. Therefore, Rema writes that we customarily use three full walls.55 Mishnah Berurah56 adds that this means that one should not utilize halachic mechanisms such as lavud57 or tzuras hapesach. Additionally, Mishnah Berurah writes that there should ideally be no gaps in the initial three walls, with the entrance being in the fourth wall. If this is not feasible, a competent halachic authority should be consulted.
Question: Must the walls actually touch the sechach?
Discussion: The walls do not have to reach the height of the sechach. Once it has the required height of ten tefachim, it is sufficient even if the sechach is much higher. This is based on the halachic principle called gud asik, which dictates that for halachic purposes, a qualified wall (i.e., one that is ten tefachim high) is viewed as extending upward endlessly.58
Laterally, however, the walls must be within three tefachim (24 cm59) from the sechach. Some maintain that even a distance of less than three tefachim is acceptable only if the walls reach the sechach’s height. If the walls do not reach the height of the sechach (which is valid, as above), they must be directly under the sechach.60 Others maintain that a lateral gap of less than three tefachim is permitted even when the wall does not reach the sechach. Strict halachah follows the lenient view.61
Question: May canvas be used for the walls of a sukkah?
Discussion: On the one hand, it is clear from the Gemara62 that a halachic wall may consist of fabrics. On the other hand, the halachah is that a wall that can be blown about by the wind is invalid.63 The Poskim explain that the invalidation of a wall blown about by the wind refers to a case where the wall swings about freely from place to place (see footnote64). However, a fabric that is firmly tied in place, such that it does not swing back and forth, is valid. This is so even if its belly flaps in the wind. Nevertheless, Shulchan Aruch65 rules that it is customary to refrain from using such walls for the three essentially required66 walls of a sukkah. This is because there is concern that the sheets will become untied without the person realizing it.67
Question: I have seen that people do commonly construct sukkos of fabric, with straps stretched horizontally across the posts that support the sukkah. What is the purpose of these straps, and do they make the use of fabric more acceptable?
Discussion: Mishnah Berurah rules that, notwithstanding the custom to refrain from making a sukkah’s walls of fabric, if the walls are augmented by three “lavud walls” that are not vulnerable to the wind, one may use them. Although a sukkah should not consist of only three lavud walls,68 they suffice to augment fabric walls. This is because “lavud walls” are only invalid on a rabbinic level. Therefore, since fabric walls are essentially valid and their use is discouraged only because they might become untied, here, where the sukkah will anyways be valid at least on a Torah level through the “lavud walls,” we are not concerned.
Question: What are the requirements of creating a sukkah of canvas augmented with “lavud walls”?
Discussion: Many prefabricated canvas sukkos come with straps to attach to the sukkah’s frame in order to create the lavud wall. Strings or the like may be used as well. In creating “lavud walls,” the following guidelines should be adhered to:
The space between one strap and the next, and between the bottom strap and the ground (or frame), must be significantly less than three tefachim (24 cm).69
The straps should be stretched as taut as possible,70 and tied securely, to ensure that they do not become undone. [For this reason, it may be advantageous to use slats of wood or the like rather than straps, since slats of wood can be securely fastened to the frame with nails in a way that they will not become loose.]
The highest strap should be at least ten tefachim (a meter71) from the ground.
In addition, one must ensure that the canvas walls themselves are valid.72 Therefore:
The canvas must be tied tightly so that it will be as minimally vulnerable to the wind as possible.
There must be no 24 cm gap between the canvas and the ground, or in between the sheets of canvas.
Notwithstanding the above, experience shows that sukkos made of canvas are often made improperly, to the extent of being truly invalid. Therefore, if possible, it is suggested not to use canvas for sukkah walls.
54. Sukkah 6b.
55. 630:5. Note: ‘Three walls’ means that the area is surrounded in three directions (270o). Therefore, a circular sukkah is considered to have three walls if it surrounds 270o.
56. 630:28
57. It is unclear whether Mishnah Berurah means that lavud should not be utilized even when there is ten tefachim of solid wall and lavud is merely required to connect it to the ground, or only when lavud is utilized to add to the necessary length or width of the wall.
58. Shulchan Aruch 630:9.
59. Assuming the calculation of R’ Chaim Na’eh, the more stringent view in this case.
60. See Mishnah Berurah 630:31; see, also, Teshuvos R’ Akiva Eiger (12); Hilchos Chag Bechag (I, p. 95).
61. As per Shulchan Aruch’s lenient ruling, ibid.
62. Sukkah 16b. This is also the indication of Shulchan Aruch (630:10), which writes that it is merely improper to use sheets for walls out of concern that they will become untied, but they are not absolutely invalid.
63. Shulchan Aruch 630:10.
64. The Poskim differ as to the precise degree blowing about in the wind invalidates a wall. Many assert that minor movement in the wind is not included in the disqualification (see, for example, Aruch Hashulchan 363:8). Chazon Ish (77:6) explains that the disqualification applies if a standard wind could blow the walls into invalid positions (e.g., lift the bottom of the wall more than three tefachim above the ground). For further discussion, see Igros Moshe, Orach Chaim V:40; Hilchos Chag Bechag, pg. 88.
65. 630:10.
66. Mishnah Berurah (630:50).
67. According to this reason, it should follow that one should not use sechach that must be tied down in order to remain in place (e.g., certain types of mats). However, such sechach certainly is used prevalently. Perhaps this restriction does not apply to sechach, since sechach is meant to be of a temporary nature. It is also possible that the concern is not as great regarding sechach, since if it becomes untied, it will be more easily noticed.
68. Mishnah Berurah (630, note 7) rules that lavud walls may be used only for a sukkah of four walls, not a sukkah of three walls; see below, footnote 31.
69. The measure of 24 cm follows the stringent view (in this instance) of R’ Chaim Na’eh in the calculation of the length of a tefach. It is important that one make the airspace significantly less, so as to leave margin for error, and also because of the eventuality of slight movement between straps.
70. This is to ensure that the straps are not too vulnerable to the wind and, also, to ensure that the full length of each string is within three tefachim of the next.
71. This measurement is used to satisfy even the stringent view (in this instance) of Chazon Ish as to the length of a tefach.
72. Note: lavud walls alone are insufficient only if the sukkah has only three walls. However, if one were to make four walls of lavud, the sukkah would be valid, according to Mishnah Berurah (ibid.), with no need for anything further. Thus, in a case where one makes four lavud walls, the canvas walls are actually not a required part of the sukkah and need not meet any requirements. Note, however, that Bikkurei Ya’akov (630:4) and Chazon Ish (75:12) do not allow for “lavud walls” even for a four-walled sukkah. According to their approach, the canvas walls would have to meet the relevant requirements in this case as well.