Q: May a non-observant Jew build a Sukkah for someone else?
A: Yes. A non-observant Jew may build a Sukkah on behalf of another Jew, including placing the Sechach, and there is no known source that prohibits this.
The discussions in the Poskim regarding women, children, and gentiles placing the Sechach are based on reasons that do not apply to a non-observant Jew. Women are exempt from the mitzvah of Sukkah, children are not yet fully obligated in mitzvos, and gentiles are not obligated in the mitzvah at all. A Jew, however, remains fully obligated in all mitzvos regardless of his level of observance.
Certainly, when building a Sukkah for himself, a non-observant Jew is obligated in the mitzvah just like any other Jew. Accordingly, there is no reason to disqualify him from building a Sukkah for others. On the contrary, since he remains obligated in the mitzvah, the rationale cited by some Poskim to prefer that the Sechach be placed by one who is obligated in the mitzvah would support his validity.
While certain halachic contexts state that a mumar or heretic is treated “like a gentile,” this is not to be understood literally in every area of Halachah. Indeed, even regarding an actual gentile, the prevailing ruling is that a Sukkah built by a gentile is valid after the fact, and the restriction against having him place the Sechach initially is itself disputed among the Poskim. Certainly, then, there is no basis to extend such concerns to a Jew who remains obligated in the mitzvah.
Furthermore, we do not find in the Talmud or Poskim any recorded custom or ruling requiring one to avoid having a non-observant Jew build a Sukkah. On the contrary, involving him in the construction of a Sukkah may strengthen his connection to Torah and mitzvos and perhaps serve as a catalyst for greater observance and spiritual growth.
Summary: A non-observant Jew may build a Sukkah for himself or for others, including placing the Sechach. The reasons cited by some Poskim to limit women, children, or gentiles from placing the Sechach do not apply to him, as he remains fully obligated in the mitzvah of Sukkah and all other mitzvos.
Sources and Basis:
The Gemara rules that a Sukkas Ganbach is valid, including a Sukkah built by women and others who are not obligated in the mitzvah. (Sukkah 8b; Shulchan Aruch O.C. 635:1).
Nevertheless, some Poskim write that initially the Sechach should be placed by one who is obligated in the mitzvah. This ruling is based on an analogy to Tzitzis and Tefillin, where certain mitzvah acts should preferably be performed by someone obligated in the mitzvah. The concern is specifically regarding women, children, and gentiles, who are exempt from or not obligated in the mitzvah. See Magen Avraham 14:3; Bikurei Yaakov 635:2; Biur Halacha 14:1 “Lehatzrich Anashim”; Kaf Hachaim 635:8.
These concerns do not apply to a non-observant Jew. A Jew remains obligated in all mitzvos regardless of his level of observance. The principle of “Yisrael af al pi shechata, Yisrael hu” teaches that even a Jew who sins retains his halachic status as a Jew and remains obligated in mitzvos. See Sanhedrin 44a.
Accordingly, all of the reasoning advanced by those Poskim who prefer that the Sechach be placed by one obligated in the mitzvah would support, rather than oppose, a non-observant Jew placing the Sechach, as he too is obligated in the mitzvah of Sukkah.
Furthermore, we do not find anywhere in the Talmud, Shulchan Aruch, or classical Poskim a restriction against hiring a non-observant Jew to build a Sukkah. On the contrary, since he personally remains obligated in the mitzvah, there is no basis to compare him to the categories listed in Ganbach.
While some halachic areas treat a mumar similarly to a gentile for specific laws, this does not create a blanket equivalence in all areas of Halachah. Indeed, even regarding an actual gentile, the Shulchan Aruch rules that a Sukkah built by a gentile is valid (Sukkah 8b; Shulchan Aruch O.C. 635:1), and the restriction against a gentile placing the Sechach initially is itself only a stringency cited by some later authorities.