Question:
For every mitzvah there is a blessing. Why do we not say a blessing when we build the sukkah?
Response:
While building the sukkah is a mitzvah, the mitzvah is not concluded until you actually dwell in it during Sukkot. Thus building the sukkah warrants no blessing of its own.
Similarly, you do not recite the celebratory Shehecheyanu blessing—which is normally required when first doing a mitzvah that you can only do occasionally—when building the sukkah. Rather, the Shehecheyanu that you will recite when making Kiddush on the first night of Sukkot not only marks the joyous onset of the holiday but is also in celebration of your sukkah.1
Wishing you a sweet new year!
Rabbi Menachem Posner
Source:
Code of Jewish Law Orech Chaim 641 and commentaries ad loc.
IMHO, these are 2 separate mitzvot. if you are undertaking a mitzvah like this, there should be a blessing you can say. It's not like there is a limit to blessings. What if you help put up a sukkah and then don't get a chance to sit/dine in one? On the other hand, what if you sit in a sukkah that you did not help build? You should get "credit" for helping build the sukkah as well as sitting/dining in one. There are blessings for seeing a rainbow and all kinds of other things, & I think that if building a sukkah is in and of itself a mitzvah, we should be able to thank God for allowing us to participate in carrying out that mitzvah. It seems to me that the mitzvah of sitting in the sukkah is a separate one; they are not automatically tied to each other, and you might be able to perform one mitzvah without being able to perform the other. Of course I'm not a rabbi and am just giving my opinion.