http://www.yeshiva.org.il/midrash/555The Succah mitzvah
Dwelling in the Succah is one of the mitzvahs of the Jewish holiday of Sukkot.
It is a mitzvah to dwell in a Succah for seven days.
It is written in theTorah (Vayikrah / Leviticus 23:42) “You shall dwell in souccot for seven days; every inhabitant of Israel shall dwell in Succot. In order that your generation shall know that I caused the Jews to dwell in Succotwhen I brought them out of Egypt. I am the Lord your G-d.” In commemoration of this we are commanded to build a sukkah in order to remember the great and wondrous deeds of G-d
When should you build your Sukkah ?
Optimally, one should start to build the soucca immediately after the Yom Kippur fast in order to fulfill the commandment “Yilchu michayil le chayil – “They go from strength to strength” (Tehilim/ Psalms 84 mart) – From the mitzvah of Yom Kippur to the mitzvah of Sukkot.
Don’t forget “Zrizim makdimim le’mitzvot” (Psachim 4) – It’s good to be an early bird for a mitzvah!
Where should you build your Sukkah?
The Succah should be built under the open skies. If it is built under a porch, tree or roof, it is not considered a kosher Succah.
The size of the Sukkah
There are no limitations to how big a Succah can be. However, the schach should not be higher than 20 Amot, or approximately 30 feet from the floor. On the other hand, the minimum size of the Succah is 24.5″x24.5″x35″ (length*width*height).
The walls of the Sukkah
A sukkah may be kosher even if it has less than three complete walls. It is customary to build a Succah with four complete walls. The walls should be strong (“Eitan”).
The walls may be made from any material. The walls should be strong enough to stay in place even when the wind blows. When the walls of the Succah are made of cloth, the cloth should be firmly attached on all sides.
The height of the Sukkah walls
The walls should be a minimum of 80cm high. They do not have to reach the height of the schach. It is permitted to support the schach on wooden posts. The remaining space may be left open. The schach should preferably reach the line directly above the wall. The walls should not be more than 24 cm above ground.
Schach for the Sukkah
Most of the Succah roof must be covered with roofing material that is kosher according to the halachic law of the sukkah. The schach eitan and strong should be made from natural materials. One should have more schach than open space. The way to determine if there is enough schach covering is to look at the sky through the roof: if you see more sun than shade then the roof is not kosher.
What is the Schach?
The schach must be made from something that grew in the earth but is no longer attached to the earth: trees, reeds, branches, etc.
Mats made of reeds (kaynes, soof), or bamboo are acceptable for schach.
One should not make the schach for a sukkah from branches with falling leaves as it will be mart unpleasant to sit in the Succah.
The raw material of the schach is something that used to grow in the past, but it has to be especially prepared for use as schach: a broomstick or wood from an old wooden fence are no good.