The blessing of Shehechiyanu said on the Sukkah:[1]

Although from the letter of the law, the blessing of Shehechiyanu should be recited when building one’s Sukkah [if it is being built within 30 days of Sukkos[2]][3], practically, it is not recited during the building of the Sukkah but rather during Kiddush on the first night of Yom Tov which is recited inside the Sukkah, and covers both the general holiday and the mitzvah of Sukkah.[4] One fulfills his obligation of Shehechiyanu even when saying kiddush in a Sukkah that is not his [such as if he is a guest in someone’s Sukkah on the first night].[5] In the event that the blessing of Shehechiyanu by Kiddush was said outside the Sukkah, such as if one said Kiddush in his house, then the blessing of Shehechiyanu must be repeated upon the next time he eats a meal in the Sukkah, as will be explained in Chapter 11 Halacha 4.[6] [Bedieved, if one recited the blessing of Shehechiyanu upon building his Sukkah, then he fulfills his obligation.[7]]

If one built a Sukkah during Chol Hamoed, is a new blessing of Shehechiyanu to be recited?[8]

No, unless it is his first time eating in a Sukkah that Holiday.

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[1] Admur 641:1; Michaber 641:1; Tur 641:2; Sukkah 46a; M”A 641:1

[2] P”M 643 A”A; Biur Halacha 641:1 “Kesheoseh”; Kaf Hachaim 641:4

[3] The reason: From the letter of the law, the blessing of Shehechiyanu should be recited when building the Sukkah that one plans on dwelling in, as it is a mitzvah that comes on occasion. Likewise, if someone else is building one’s Sukkah for him, it is proper that he the owner of the Sukkah who will dwell in it during Sukkos, say the blessing of Shehechiyanu at the time that it is being built. The reason for this is because the main blessing was established on the joy that a person receives from an uncommon mitzvah that only comes on occasion, and the main joy is to the owner of the Sukkah and not to the person who makes it. [Admur ibid] See Biur Halacha 641:1 “Liatzmo”;

[4] The reason: The custom is not to say the blessing of Shehechiyanu at all when building the Sukkah even when one is building his own Sukkah, being that we rely on the blessing of Shehechiyanu will be recited during kiddush of the night of Yom Tov for the sake of the mitzvah of sanctifying the holiday, which is also a mitzvah that comes only on occasion, and deserves a blessing of Shehechiyanu. Now, this blessing of Shehechiyanu said during kiddush counts for both Mitzvos. [Admur ibid]

[5] Admur 641:2; Kaf Hachaim 641:11

[6] Admur 641:2

[7] Rama ibid; See Poskim in Biur Halacha 641:1 “Ela” and Kaf Hachaim 641:7 regarding if the blessing of Shehechiyanu is to be repeated in Kiddush in such a case

[8] Mikraeiy Kodesh Sukkos 1:25; Betzel Hachochmah 5:171; Kinyan Torah 4:76; Shraga Hameir 5:72; Piskeiy Teshuvos 641:2