This Halacha is an excerpt from our Sefer
Homes-Moving & renovations
Moving during the three weeks:
If doing so is possible, one should abstain from moving houses throughout the duration of the three weeks, until the 15th of Av.
May one purchase a home during the three weeks?
One is not to do so unless it is an absolute necessity or a case of loss.
May one sign a contract to purchase or rent a home during the three weeks?
May one renovate, or paint, his home during the three weeks?
Some Poskim rule it is proper to abstain from renovating or painting one’s house throughout the three weeks. Starting from Rosh Chodesh Av, it is forbidden to do so from the letter of the law, as explained in Chapter 3 Halacha 5. See there!
If one began painting or renovations prior to the three weeks: If one began painting or renovations prior to the three weeks, then even according to the above opinion, he may continue the job past the 17th of Tammuz. He may do so up until the start of the nine days. However, some Poskim allow one to complete the job up until the week of Tisha B’av.
House is damaged: The above prohibition and stringency only apply if one desires to paint and renovate for pleasure purposes. If however the house and paint is damaged, such as due to a leak or fire and the like, then it may be painted and renovated throughout the three weeks, even during the week of Tisha B’av.
 Igros Kodesh 9:228; 19:390 [brought in Shulchan Menachem 3 p. 48; Sha’arei Halacha Uminhag 2:225]; Not found in other Poskim.
 The reason: Seemingly the reason for this ruling is because one is to avoid doing things that change his Mazal during a period of time that a Jews Mazal is bad, just like one is to avoid judgment with a gentile during this time. Alternatively moving is included within matters of joy and one is to avoid doing matters of joy until the 15th of Av. The reason for why after the 15th of Av there is no need to refrain from moving, seemingly is because it follows the ruling of the Chasam Sofer 551 regarding avoiding judgment that it only extends until the 15th.
Not to move at all during Av: In another letter the Rebbe writes one is to avoid moving throughout the month of Av and is rather to try to move in Elul, the month of mercy. [Igros Kodesh 19:390] This follows the ruling of the M”A 551:2 that the bad Mazal of Av extends throughout the month.
 See Admur Seder 12:2 that Shehechiyanu is recited over purchasing a new home and hence its purchase is to be avoided during the three weeks.
 Nitei Gavriel 28:11; Levushei Mordechai 1:101
 This is permitted even during the nine days, as the prohibition is only against building, and not against buying, and it was already explained in Halacha 2 that we are lenient to allow business to continue as usual during the nine days, so long as it is not of Simcha. [ibid]
 Piskeiy Teshuvos 551:8
 Elya Raba 551:4 in name of Mahril based on Michaber ibid who wrote “It is forbidden during the nine days …. Or a building of design and fashion” and he applies it also to the three weeks, and this includes painting.
 Elya Raba ibid
 Piskeiy Teshuvos ibid based on M”B 551:12
 Igros Moshe 3:82
 See Michaber 551:2; Piskeiy Teshuvos ibid in name of Rav Moshe Halbershtam