Q. Is it permitted to wash the house floor during the nine days? How about the deck outside if dirty?

A. In question 594 on this forum we wrote; Although you may vacuum clean a carpet during the Nine Days, even a Gentile should not wash them. In regards to washing the floors Poskim disagree. Some maintain that it is permitted. (Teshuras Shai 174.) Some permit only for someone who does so every week, (Hisorerus Teshuvo O.H. 339) and some prohibit altogrther. (Meshiv Devorim Y.D. 259, Divrei Sofrim 146.) Nitei Gavriel (Ben Hametzorim 1:29:7) writes that it is accustomed to be stringent, however, for the honor of Shabbos it is permitted.
Horav Shlomo Miller’s Shlit”a opinion is that it is permitted in need or when done so every week.
In regards to the deck outside, on question 595 we wrote: Horav Shlomo Miller’s Shlit”a opinion is that the Nine Days should be dedicated essentially to the mourning of the Bais Hamikdosh and what we should do to bring about a prompt Geula. Having said that, if there is a need to pressure wash a deck or outside walls (as in a cottage,) it is permitted since it is not included on the laundering prohibition.
(See also question 337 in this forum permitting washing a car during the Nine Days)

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a