Shulchan Aruch Chapter 625:  The Laws of Succot (1 Paragraph)
Note:  REMA in brackets []

1.  The Torah writes "In Succot though shall dwell for 7 days etc."  "In Succot I protected the children of Israel"; these refer to the clouds of glory who protected them from all the intense heat and the sun of the desert.  [And it is a Mitzvah to begin building the Succah immediately after Yom Kippur.  For if a Mitzvah that comes to one's hands, one should not delay performing it.]

Shulchan Aruch Chapter 626:  If One is Able to Build a Succah Under a Tree or a Roof (3 Paragraphs)

1.  [One may not build a Succah under  a house (roof) or under a tree.]  One who builds a Succah under a tree, some say that if the foliage blocks most of the sunlight it is invalid.  The same applies to the Succah itself, that if the roof (סכך) of the Succah blocks most of the sunlight it is invalid.  These Rabbis say that if the tree's foliage lets most of the sunlight through it is Kosher.  But the Succah built below it must let most of the sunlight through as well.  (The author is now talking about a case where the tree's branches are lying directly on top of the סכך.  This will be followed by a case where there is air between the branches and the סכך.) The Succah is valid even if one did not take the tree's branches and mix it with the סכך of the Succah in such a way that one is unable to tell the difference between the branches of the tree and the סכך of the Succah according to this opinion.  Others hold that the Succah is invalid if the branches of the tree are recognisible that they are from the tree and not part of the סכך in such a case. [So if one bends the branches of the tree down and mixes them with the סכך in order that one does not see a difference between them then it is Kosher.  Similarly, if one takes a valid סכך and puts it on top of invalid סכך the Succah is called "mixed" and it is valid.]  If one built a Succah סכךunder a tree with foliage that lets most of the sun through, and the tree's branches are above the סכך with air between them, then the Succah is valid since if one would remove the tree, there would still be enough סכך to make it valid.  [Or if one has a lot of סכך that even if one removed the tree, enough is left to be valid.]  It does not make a difference if the tree was put on first or the סכך was put on first, the same law applies.

2.  If one used only a tree's branches for סכך while it was still attached to the tree and then cut the branches off, it is valid.  This only applies if he put the branches on the Succah originally with the intention of using them for the Mitzvah of Succah.  But if not, it is invalid because of תעשה ולא מן העשוי "it must be made but not from something that is already made for a different purpose".  [But it is permitted to build a Succah under a house or some structure and later remove that structure and it is not called תעשה ולא מן העשוי since the thing that is invalid is not in the סכך itself.]

3.  If one builds a Succah under a house and removes the roof, even if one leaves the supporting rafters and puts סכך on top of them it is still valid.  [It is also valid to build a Succah under roofs that are made to open and close.  It is permitted to close them because of the rain and come back later and open them up.  Even on Yom Tov it is permitted to open and close them if they have gears which operate the opening and closing.  One is not liable for destroying or building a tent on Yom Tovand תעשה ולא מן העשוי does not apply as well.  However, one must be careful to not sit under the Succah while the roof is being closed, because then the Succah beomes invalid.]

Shulchan Aruch Chapter 627:  The Laws of Sitting in the Succah (4 Paragraphs)

1.  [One must sit inside the Succah.]  In a case where one sleeps under a bed in the Succah; if it was higher than 10 handbreaths he does not fulfill his obligation. 

2.  One who sleeps on a bed surrounded by a bed frame in the Succah, it is valid as long at is is not higher than 10 handbreaths and as long as it doesn't have something above it as wide as a handbreath or more. 

3.  One may not put walls around the four bed posts at the corner of the bed and sleep in it even if they are not higher than 10 handbreaths.  But if one builds a beam in the middle of the bed and builds walls around it in such a way that the entire roof is not wider than one handbreath it is valid (unsure of exact translation ???).  This is only if it is not higher than 10 handbreaths.  Some validate it even if it was higher than 10 handbreaths. 

4.  If one hangs anything under the סכך for decoration, if it is within 4 handbreaths from the סכך then it is Kosher, but if it is beyond 4 handbreaths from the סכך it is invalid (to sit under).  If they were not for decoration, then even if they were within 4 handbreaths, it is invalid.  [One must be careful to only hang decorations within 4 handbreaths of the סכך. ]

Shulchan Aruch Chapter 628:  The Laws of a Succah Under a Succah (3 Paragraphs)

1.  If one built a Succah under a Succah, the one on top is valid, but the one on the bottom is invalid.  This is only if one is able to put his provisions there to eat and sleep even tightly and 10 handbreaths of free space remain on top.  But if there is not 10 handbreaths between them or if the lower Succah is not able have enough space for his provisions, the lower one is valid (and the upper one is invalid) as long as it is made according to Halacha.  Even if the top Succah is highter than 20 cubits and it was built invalid, the lower one is valid.  But in order for the lower Succah to use the סכך of the upper Succah, the upper succah can not be higher from the ground more than 20 cubits.

2.  If one builds his Succah on a wagon or on a boat, if it is not able to stand in a normal wind that occurs on land then it is invalid.  But if it is able to stand up in a normal wind on land then it is valid; even if it can not stand on a normal sea wind. 

3.  If one builds a Succah on the back of a camel or on the branch of a tree, it is valid.  But one is unable to go into it on Yom Tov.  If part of it was built in a tree and another part of it was built on something else, one may go into it on Yom Tov if the Sucah would be able to hold by itself if the tree was removed.
Translated by Dr. Jay Dinovitser
Free for Personal Use