A temporary dwelling for the purpose of shade:
A. The Sukkah must be made only in order to give shade:1
Just as the clouds of glory were there to give us shade from the sun, similarly the Sukkah is only valid when made in order to only give shade. If it was made to serve for also other purposes, such as storage and the like then it is not considered a Sukkah but rather a house and is inherently invalid.
B. An old Sukkah-If one has a Sukkah throughout the year must he do anything to it before Sukkos, or may it be used in its current state? 
Built for the sake of the Mitzvah: A Sukkah which was built for the purpose of fulfilling the Mitzvah is valid even if it was built towards the beginning of the year, meaning directly after Sukkos for use the next Sukkos holiday. [Thus if one never took down the previous year’s Sukkah, it may be used for the current Sukkos holiday without needing any modification.
Built for the sake of shade-not for the Mitzvah: If the Sukkah was built for the sake of shade, then if this was done within thirty days before Sukkos, it is valid. If it was made prior to 30 days before Sukkos, one must renew something in the Sukkah for the sake of the Mitzvah. The definition of a renewed action is to place new Sechach at least the size of 1×1 Tefach for the sake of the Mitzvah, or to place Sechach from one end of the Sukkah to another even if it is less than one Tefach. Regarding the walls, even if they were made from the beginning of the year for shade, one does not need to renew anything for it to be valid and renewing the Sechach suffices.
C. A Sukkah which is one’s house-Is a Sukkah valid if it serves as one house throughout the year?
If the Sukkah is used as a dwelling place it is invalid and the Sechach must be lifted and placed back on each year before Sukkos. [Thus a Sukkah that is built in ones house under a retractable roof and left intact the entire year since one lives in this Sukkah throughout the year he is required to renew the Sechach each year before Sukkos.] It suffices to simply lift up the Sechach and place it back down.
 This ruling follows the explanation in the previous chapter [625/1] with regards to the purpose behind the clouds of glory “that it was done for shade”. This explains why a) Admur mentions the term shade in the previous Halacha despite it not being found in the Tur and Michaber. B) Why Admur began to is chapter with the current Halacha despite the fact that it is not mentioned in this chapter by the Tur/Michaber. As according to Admur the main aspect of a Sukkah is that it is made only for shade and thus when this is lacking it is not simply lacking a detail within Sukkah, but rather it itself is not a Sukkah at all. [Shaar Hamoadim]
 The reason: It is invalid due to it becoming a permanent dwelling.
 Admur ibid; M”B 636/8
Other Opinions: However the Chelkas Yaakov 3 rules the Sechach is completely invalid and must be replaced. [Piskeiy Teshuvos 636/2]