The sukka is used throughout the festival and it is the focal point of the holiday.

In constructing a sukka, one must pay attention to several factors: its location, its dimensions, the structure of the walls, and the correct form of its roofing [sekhakh]:

A central principle in the halakhot of sukka construction is that the roofing of the sukka is meant to provide shade for those who dwell in it. Therefore, it is imperative that the sukka be built under the open sky, not beneath a house or tree or anything else. If this rule is not followed, the sukka is invalid.

It is preferable that the sukka be built on one’s private property, not in the public domain. Nevertheless, a sukka that was erected in a public area is valid. It should be noted that one may not use another person’s sukka without permission.

The minimum dimensions of ​​a valid sukka are seven by seven handbreadths, which is about 56 x 56 cm. On the other hand, there is no upper limit to the area of a sukka; it can be as large as one wants. The minimum height of a sukka is ten handbreadths, roughly eighty cm, while the maximum height is twenty cubits, approximately 9.6 meters.

The walls of a sukka may be built from any material, and one may even use the pre-existing walls of a building. One must be particular about several matters: the number of walls, their size, and their strength.

A sukka must have at least three walls; the fourth side may be left open. Two of the walls must be complete, extending along the entire side of ​​the sukka, while the third wall may be a partial wall; that is, it does not have to cover the whole side of the sukka. Nevertheless, it is preferable to avoid having a shorter third wall, and to erect a sukka with at least three full walls.

When there is no other option, one may make do with the partial third wall mentioned above, but one must ensure that the following three conditions are fulfilled: (1) The partial wall must adjoin the end of one of the two whole walls; (2) the minimum width of the partial wall must be 8 cm; (3) an additional post should be placed opposite the end of the wall parallel to the short wall, and one should place a string or bar above it that will run from this post to the short wall (see diagram).

If the two complete walls are parallel to each other, the short wall should be adjoined to the edge of one of them, and a string or bar should be placed above it, running from there to the top of the opposite complete wall (see diagram).

The minimum height of the walls of a sukka is ten handbreadths (about 80 cm). A wall of this height is valid even if there is a gap between the top of the wall and the roofing, provided that the bottom of the wall is on the ground or within three handbreadths of the ground.

It is permitted to have open spaces or gaps in the walls of the sukka to serve as entrances and windows. When building a large sukka, one must make sure that the width of each of the spaces is no greater than ten cubits, 4.8 meters.

The walls should be strong enough to last for the entire festival. Therefore, they should not be made of materials that might get worn out or disintegrate over the course of the holiday. Additionally, the walls may not be so loose that they sway in the wind in normal weather. Accordingly, if one uses canvas or cloth sukka walls, he should tie them down firmly so that they will not move in the wind. To be on the safe side, it is advisable in such circumstances to tie a taut string along each of the walls of the sukka, from corner to corner. The strings should be tied no more than 24 cm apart from each other, and the highest one should reach a height of 80 cm (see diagram). Because of a halakhic concept known as levud, these strings can actually be considered walls due to the fact that the space between them is less than three handbreadths.

There are sukkot on the market that are very easy to assemble and that come with the necessary materials to address this issue.

Another relevant discussion pertains to a case where there is a horizontal gap between the sekhakh (sukka roofing) and the wall. If the sekhakh simply does not reach the wall and there is empty space between them, the sukka is still valid as long as the space is less than three handbreadths, approximately 24 cm.

However, if that part of the sukka is covered by materials invalid for sekhakh (see diagram), the wall of the sukka is viewed as a “bent wall” [dofen akuma] that includes this section of the roof. In such a case, as long as the invalid sekhakh extends no more than four cubits (approximately 1.9 m) beyond the wall, the sukka is valid. However, it should be noted that one may not eat underneath this section. This law applies even if the invalid materials are located above the roof of the sukka. Common applications of this law include situations where branches of a tree, a porch, or an air conditioning unit cover part of a sukka.

Not all materials may be used for the sukka roofing, or sekhakh. In order for the sekhakh to be valid, the following requirements must be met:

The material from which the sekhakh is made must grow from the ground but no longer be attached to the ground.

However, wooden utensils, edible items such as fruit, and reed mats that are made to be used as carpets are all invalid for sekhakh. By contrast, mats that were produced specifically for roofing, such as those that are widely available at stores where Sukkot supplies are sold, are valid. A rabbi should be consulted about the halakhic status of mats whose intended purpose is unknown.

The sekhakh, like the walls, must be durable enough to last throughout the festival, so that it does not dry out and shrink, thereby creating gaps that will let in sunlight.

As for the validity of pergolas for sekhakh, one should consult with a rabbi concerning each specific case.

The density of the sekhakh

The sekhakh must be dense enough to ensure that there is more shade in the sukka than sunlight. A very dense thatch does not invalidate the sukka, provided that rain can penetrate, but it is proper to leave a few cracks.

For the sake of providing shade

The sekhakh must have been put in place for the purpose of providing shade. Consequently, if roofing was already there beforehand – for example, if branches fell on the sukka from a nearby tree, or a vine climbed up over the sukka and it was later detached from the soil – the roofing is invalid. It is possible to render such roofing valid by lifting it up from the sukka and placing it down again, this time for the purpose of serving as sekhakh.

It is customary to decorate the sukka as an enhancement of the mitzva [hiddur mitzva]. When decorating it, two factors must be taken into account: First, the sukka decorations, like the structure of the sukka itself, are considered sanctified throughout the seven days of the festival, and therefore they may not be used for any other purpose during this time. Second, any decorations hanging from the sekhakh must be placed close to it, so that the distance between the sekhakh and the decorations does not exceed four handbreadths (32 cm).