What makes a sukkah kosher — the walls, or what goes on the roof?

Here's what you need to know

A kosher sukkah needs both: at least three sturdy walls to enclose the space, and schach (the roof covering, made of cut plant material) laid over it. Neither one alone makes a valid sukkah; they are two separate requirements that both come from the Torah.

The specific rule is

Both the walls and the schach (roof covering) are required for a sukkah to be valid (kosher). The walls create the enclosed space, and the minimum is three of them, though there is a recognized technical configuration in which the third is only a narrow strip set close to one of the others; most sukkahs are built with three or four full walls instead. The schach, cut plant material laid loosely on top, is what turns that enclosed space into a sukkah rather than an ordinary room. Missing either element invalidates the whole structure.

Step by step

• Put the walls up first: at least three of them, sturdy enough to hold in an ordinary wind.
• Check the height: at least 10 handbreadths (roughly 32 inches) tall, with the interior no more than 20 cubits.
• Choose schach that grew from the ground and is now fully cut off from it, such as branches, bamboo, or reeds.
• Make sure the schach isn't something manufactured into a finished vessel, and isn't metal, plastic, or food.
• Lay the schach loosely over the walls so that more shade than sunlight falls inside.

Background

The walls need to stand up to an ordinary wind and reach at least 10 handbreadths (roughly 32 inches) tall, and the sukkah's interior may not be more than 20 cubits high. The strict minimum is three walls, and there is a recognized configuration in which the third is only a narrow strip positioned close to one of the others, but that minimal version is a technical leniency rarely relied on; most sukkahs are built with three or four full walls.

The schach must be something that grew from the ground and has been cut off from its source of growth: branches, bamboo, reeds, or similar plant material. It cannot be a manufactured item, metal, plastic, or anything that has become a finished vessel or food susceptible to ritual impurity (tumah). It must be laid on top of the walls without being tied into thick bundles in a way that suggests it is meant as ordinary building material rather than as a sukkah covering.

Two further schach rules matter in practice. There must be more shade than sunlight coming through when you look up. And gaps matter: a stretch of invalid covering, or of open air, invalidates what sits beneath it once it reaches a certain width, but the width that does it depends on where the gap falls and how big the sukkah is. A roof with real gaps in it is worth measuring and asking about rather than eyeballing.

Both requirements, walls and schach, are Torah-level (mitzvah min haTorah), which is why a structure missing either one isn't a flawed sukkah, it simply isn't a sukkah. This is foundational, with no real difference of practice across communities, though the fine details of wall height, wall materials, and how much shade counts as "more shade than sun" involve technical measurements best confirmed with a rabbi when building or evaluating a specific structure.

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