Over time, Haussmannian buildings have been continuously subjected to conservation works, particularly considering their age and deterioration level. In recent years, several apartment buildings have been converted into luxury hotels and existing ones have been renovated due to an increasing demand for accommodation, resulting in heavy repair, rehabilitation and strengthening works. Haussmannian architecture is an invaluable asset of Paris urban character and distinctiveness, and conservation interventions should be carried out accordingly. This paper describes the rehabilitation and strengthening works best practices undertaken during these interventions. In this context, a reference to protection measures to ensure the preservation of buildings registered on the list of historic monuments is done, as well as a reference to regulatory-based and incentive-based programmes to prevent abandonment and lack of maintenance. This paper is based on the experience gained during construction projects that the author has worked on in France. The techniques and methodologies presented in this paper should be considered good conservation practices and included in maintenance programmes, but also to support the development of innovative and sustainable rehabilitation and strengthening techniques, aiming to preserve this important building heritage and similar ones existing in other countries.