Mishnah/Seder Moed/Tractate Sukkah/Chapter 1/1
A sukkah which is taller than twenty amot is unfit for use, [however], Rabbi Yehudah permits it.
One which is not ten tephachim tall, or which does not contain three walls or which has more sun that shade, is unfit for use.
[Regarding] an old sukkah- Beit Shammai forbid it and Beit Hillel permit it. What is an old sukkah? Anything which he made, thirty days before the festival [of Sukkot].
However, if he made it for the sake of the festival, even [if he made it] from the beginning of the year, it is fit for use.