May a child above Bar Mitzvah place the Sechach on the Sukkah even though it is unknown if he has grown the signs of puberty? Yes.[1] However, some Poskim[2] are stringent even in such a case. [1] P”M 14 A”A 3 [2] Sefer Hasukkah Hashaleim Miluim 11:10 in name of
May a child above Bar Mitzvah place the Sechach on the Sukkah even though it is unknown if he has grown the signs of puberty?
Yes.[1] However, some Poskim[2] are stringent even in such a case.