Question:
May one who began renovations before the Three Weeks continue the work during the Three Weeks and the Nine Days?
Answer:
During the Three Weeks, although it is proper to refrain from renovations, if one already began the work before the 17th of Tammuz, he may continue until the start of the Nine Days. Furthermore, even during the Nine Days, one may continue renovations if the work is an absolute necessity for living needs. Additionally, if the home is damaged (e.g., due to leak or structural issue), repairs may be done even during the Nine Days, including the week of Tisha B’Av. If it is not necessary but stopping will cause a financial loss, then the work may continue through a non-Jewish worker.
Accordingly, continuing renovations depends on the nature of the work: necessity allows continuation, financial loss may allow continuation through a non-Jew, and purely aesthetic projects should be halted.
Sources:
Shulchan Aruch Orach Chaim 551:2; Rama ibid; Magen Avraham 551:7; Makor Chaim 551:2; Elya Raba 551:4; Levushei Mordechai 1:101; Aruch Hashulchan 551:7; Mishnah Berurah 551:12; Dvar Yehoshua 2:73; Igros Moshe Orach Chaim 3:82; Nitei Gavriel 28:4–8; Piskei Teshuvos 551:8; Shearis Yaakov 38