Daf Yomi - Sukkah 22 - Keep the rain out

The Rishonim debate what the halacha would be if one constructed his Sukkah and placed the s’chach in a manner that rain would not be able to enter the Sukkah. Rashi is quoted as maintaining that the Sukkah is still valid and Rabbeinu Tam disagrees and maintains that this would be similar to a house and the Sukkah would be invalid. There is a question that is asked on the opinion of Rashi. Shulchan Aruch Orach Chaim 640:4 rules that one should not use branches from a thornbush for s’chach because if the leaves fall into the Sukkah, one will be distressed and this will cause him to exit the Sukkah. Similarly, one cannot construct his Sukkah in a place that has a fetid smell because this will cause him to be uncomfortable and he will be exempt from his obligation. Following this logic, according to Rashi who maintains that a Sukkah is still valid if the rain cannot enter, it would seem to be preferable that one should place the s’chach in a manner that the rain cannot enter into the Sukkah. Thus, even if it does rain, he will be protected and he will be able to remain in the Sukkah. The answer to this question can be that there is a distinction between the cases. Using s’chach from a thornbush or positioning a Sukkah in a location where there is no smell is not prohibited, so logic would dictate that one build his Sukkah in a way that will not cause him distress and anguish. It is not preferable to place thick s’chach on a Sukkah, however, because then the Sukkah is similar to a house. Although Rashi validates the Sukkah ex post facto, it is still preferable not to build it in such a manner.