A kosher sukkah should have three walls. Each wall should be at least 28 inches wide. As the Gemara and Shulchan Aruch say, at least seven by seven tefachim. Each wall should be at least 40 inches high. One has to be very careful to make sure that the wall comes at least within nine inches of the ground. So if you have a space between the wall of your sukkah and the floor on which the sukkah is constructed, you need to be sure that there is no space of nine inches or more.
On top of the sukkah, you need to have s'chach. S'chah is something that grows from the ground and also something that's not mekabel tumah. So you can't use wood, or pieces of furniture, such as wooden chairs. That would be disqualified because the only items that could be used for s'chach are items that are not already-made vessels, instruments that are mekabel tumah, because at that point they are not kosher for s'chach.
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