An old succah is a succah whose s'chach was placed upon it thirty days prior to the Yom Tov. For at such an early date we assume that the s'chach was not placed upon the succah for the expressed purpose of the Yom Tov. However if in fact he did place the s'chach upon the succah for the purpose of using the succah for Yom Tov then we say that it would be kosher even if placed at the beginning of the year. He would also not be obligated to renew anything in the s'chach before Yom Tov. (For further explanation see further questions 3-8) (Shulchan Aruch section 1, M.B. section 1, 3,).
However a succah that is standing for a while on which is added new s'chach every year is not considered an old succah.
2. What would the halachah be in reference to a succah that was built within thirty days of Yom Tov without any expressed thought that it should be for Yom Tov?
Since we are required to start learning the halachos of the Yom Tov within thirty days of the Yom Tov we assume that the succah was made with the Yom Tov in mind (M.B. section 2).3. Are there any specific halachos in reference to an old succah?
The Shulchan Aruch writes that an old succah is kosher provided that something is renewed in the s'chach for the coming Yom Tov. This means that additional s'chach should be placed upon the succah for Yom Tov. Another option would be to lift up a specific amount of s'chach (see next question) and then replace it for the mitzvah of succah (Aruch Hashulchan in name of Taz and Magen Avrohom). The reason for this halachah is in order to prevent people from thinking that a succah originally made as a dwelling place is kosher. For such a succah would definitely have a Torah prohibition (as stated before chapter 11 question 1, also M.B. section 4)Next Chapter