Succah 2:2-3

Succah 2:2

If someone’s succah rested on the legs of a bed, it is valid, though Rabbi Yehuda says a succah is invalid if it cannot support itself. If a succah’s schach is disorderly (allowing in too much sunlight because it is not properly arranged) or there is more shade than sun, it is valid. If the schach is thick like the roof of a house so that the stars are not visible, it is valid.

Succah 2:3

A succah on a wagon or a boat is valid and one may enter it on yom tov. A succah in a tree or on a camel is valid but one may not enter it on yom tov. If two of a succah’s walls were formed by a tree and one was manmade, or vice versa, the succah is valid but one may not enter it on yom tov (because we may not make use of a tree on yom tov). If there are three manmade walls and a tree provides the fourth wall, it is valid and one may enter it on yom tov (because a succah only requires three walls and the fourth is superfluous). The general principle is that if removing the tree would leave the succah standing, it is valid and one may enter on yom tov.