24 C.F.R. § 884.219
If HUD or the PHA, as the case may be, determines that a Contract unit assisted under this part is not Decent, Safe, and Sanitary by reason of increase in Family size, or that a Contract unit is larger than appropriate for the size of the Family in occupancy, housing assistance payments with respect to such unit will not be abated, unless the Owner fails to offer the Family a suitable unit as soon as one becomes vacant and ready for occupancy. In the case of an overcrowded unit, if the Owner does not have any suitable units or if no vacancy of a suitable unit occurs within a reasonable time, HUD (or the PHA) will assist the Family in finding a suitable dwelling unit and require the Family to move to such a unit as soon as possible. The Owner may receive housing assistance payments for the vacated unit if he complies with the requirements of § 884.106(c)(1) .
24 C.F.R. §884.219