Objective. To assess the association of family and housing characteristics with the number of seropositive cases to SARS-CoV-2 in households. Materials and methods. We analyzed 874 households from Encuesta Nacional de Salud y Nutrición (Ensanut) 2020 Covid-19 using Poisson regression models. Results. The number of seropositive family members was higher among families composed of children/adolescents, adults and older adults, households with more than two members per bedroom, and among households with closed windows. No association was found for bathroom availability and piped water. Conclusions. Family composition and housing characteristics can impose significant structural barriers to safe home confinement.