1. The Mitzvah of building a Sukkah:
It is a command in the Torah to dwell in a Sukkah throughout the seven days of the Sukkos Holiday. As a result of this command, we are required to build a Sukkah prior to Sukkos in order to fulfill the command when the time arrives, and it is thus considered a Mitzvah to do so. Nonetheless, the building of the Sukkah is only considered a preparatory Mitzvah [i.e. Hechsher Mitzvah] as opposed to a Mitzvah with intrinsic value, as it is built simply for the purpose of later fulfilling the Mitzvah of dwelling in it during the holiday of Sukkos. Accordingly, no blessing is recited upon building the Sukkah, in contrast to the ruling by other Mitzvos in which a blessing is said prior to its fulfillment, as explained next.
Saying a blessing: One who builds a Sukkah does not recite a blessing upon building it. Meaning that a blessing of “Asher Kidishanu Bemitzvosav Vetzivanu Lasos Sukkah” is not recited, even though it is commonly recited upon the fulfillment of other Mitzvos. This applies whether one builds a Sukkah for himself to dwell in it during the festival, or on behalf of others for them to dwell in it during the festival.
 Piskeiy Teshuvos 625:1; 640:7
 See Admur 625:1 who calls it a Mitzvah “It is a Mitzvah to build..as a Mitzvah that comes to one’s hands..”; 641:1 “The Sukkah is not the completion of the Mitzvah” which implies that nonetheless it is the start of the Mitzvah; Rambam Brachos 11:8 “Any Mitzvah that contains another Mitzvah after doing it.”; See Menachos 42b; Rashi Makos 8a; Yerushalmi Brachos 9:3 that even a blessing is recited; Avnei Nezer O.C. 459 that even according to the Bavli there is a Mitzvah to do so; Emek Sheila on Sheilasos Mitzvah 169; Likkutei Sichos 17 p. 188 footnote 56 that even according to the Bavli there is a Mitzvah to do so; See Mikraeiy Kodesh Sukkos 1:25; Kinyan Torah 3:90; Moadim Uzmanim 1:80; Mishneh Halachos 8:237; 10:72
Other opinions: Some Poskim rule that a Hechsher Mitzvah is not considred a Mitzvah at all. [See Chasam Sofer Y.D. 10; Chelkas Yoev 27; Minchas Elazar 4:55]
 Admur 641:1 “The building of the Sukkah is not the completion of the Mitzvah, as the main Mitzvah is only fulfilled when when dwells in the Sukkah during the holiday itself”; Chasam Sofer Y.D. 271; Chelkas Yoev 27; Minchas Elazar 4:55; See Menachos 42b; Piskeiy Teshuvos 641:1; So rule regarding Tzitzis: Admur 19:1; Michaber 19:1; Menachos ibid
Other opinions: Some Poskim rule that a Hechsher Mitzvah is also considered a Mitzvah in its own right. [Yerushalmi Brachos 9:3; Avnei Nezer O.C. 459 that so agrees also Bavli; See Biur Halacha 656 “Afilu” and Likkutei Sichos ibid]
 Admur 641:1; Kunturs Achron 263:3; Michaber 641:1; Rambam Brachos 11:8; Menachos 42b “Laasos Sukkah is not recited”; Sukkos 46a; Tosafus Sukkah 46a; So rule regarding Tzitzis: Admur 19:1; Michaber 19:1; Menachos ibid
Other opinions: The Yerushalmi rules that one is to recite a blessing upon building the Sukkah. [Yerushalmi Brachos 9:3 “One who makes a Sukkah for himself says the blessing of Asher Kidishanu Bemitzvosav Vetzivanu La’asos Sukkah”]
 The reason: As the building of the Sukkah is not the completion of the Mitzvah, as the main Mitzvah is only fulfilled when when dwells in the Sukkah during the holiday itself. [Admur ibid and in Kuntrus Achron ibid] Vetzaruch Iyun from Bedikas Chameitz, in which case we a blessing is recited at the time of Bedika even though the Mitzvah is only fulfilled the next day.