PROTOCOL: An evidence and gap map of studies of implementation issues for interventions for those affected by and at risk of homelessness in high-income countries.

This is the protocol for a Campbell systematic review. The objectives are as follows. The proposed evidence and gap map will present relevant process evaluations and other studies of barriers and facilitators, both qualitative and quantitative, for eligible homelessness interventions to highlight the issues arising in the implementation of these interventions. Specifically, the objectives of the map are to: (i) develop a clear taxonomy of interventions and implementation issues (e.g., barriers and facilitators-factors which works as barriers to hinder successful implementation of policies and programmes and factors which facilitate the intervention and therefore support its implementation) related to homelessness in high-income countries; (ii) map available systematic reviews and primary studies of the implementation issues of interventions for those experiencing homelessness and those at risk of homelessness, with an overview provided in a summary report; (iii) provide a searchable database of included studies accessible to research users via CHI website.