BackgroundHousehold smoke-free home rules cannot fully protect nonsmokers from secondhand smoke (SHS) if they live in multi-unit housing (MUH). Instead, property-level smoke-free policies are needed to prevent SHS incursion into apartment units and to keep common areas smoke-free. Smoke-free policies are usually at the discretion of property management companies and owners within the context of market-rate and privately-owned affordable housing in the U.S.MethodsSemi-structured interviews on the policy development, implementation and enforcement experiences of 21 different privately-owned affordable housing management companies were conducted with representatives from properties in North Carolina and Georgia who had established smoke-free policies before 2016.ResultsThe decision to adopt was typically made by corporate leadership, board members, owners or property managers, with relatively little resident input. Policy details were influenced by property layout, perceptions of how best to facilitate compliance and enforcement, and cost of creating a designated smoking area. Policies were implemented through inclusion in leases, lease addenda or house rules with 6 months’ notice most common. Participants thought having a written policy, the norms and culture of the housing community, public norms for smoke-free environments, and resident awareness of the rules and their consequences, aided with compliance. Violations were identified through routine inspections of units and resident reporting. Resident denial and efforts to hide smoking were shared as challenges to enforcement, along with a perception that concrete evidence would be needed in eviction court and that simply the smell of SHS was insufficient evidence of violation. Over half had terminated leases or evicted residents due to violations of the smoke-free policy. The most common benefits cited were reduced turnover cost and time, and lower vacancy rates.ConclusionsUnderstanding the smoke-free policy process in privately-owned affordable housing can help practitioners encourage policies within subsidized housing contexts. The study identified salient benefits (e.g., reduced cost, time, and vacancies) that can be highlighted when encouraging MUH partners to adopt policies. Additionally, study findings provide guidance on what to consider when designing smoke-free policies (e.g., layout, costs), and provide insights into how to enhance compliance (e.g., resident awareness) and manage enforcement (e.g., routine inspections).