Raising buildings is one of the solutions implemented by social landlords to deal with the housing crisis. Less cumbersome than a demolition-construction operation, it allows them to start from what already exists to increase the number of homes offered for rental, while improving the profitability of their real estate stock. The example of the capital is particularly telling, where operations have been increasing for several years, facilitated by the Alur law of 2014 which lifted some of the regulatory barriers restricting construction at height. In Paris, elevations most often target small to medium-sized residences, which they extend by one to two, or even three levels.
They are often carried out in conjunction with a rehabilitation of existing parts. These are complex projects that must be shoehorned into small plots of land, subject to strong constraints (neighborhood, security).
They require a careful preliminary diagnosis to determine the condition and load-bearing capacity of the old building, and guide possible reinforcement work. Operations also require a certain agility in the application of regulations affecting new construction and rehabilitation. In practice, the work uses lightweight structures (wood, metal) which limit the impact on the existing structure. Both concrete and masonry are used more occasionally, for example to extend a circulation core or create bracing. The rise in requirements from social landlords in terms of thermal performance results in highly insulating envelopes to maximize the use of biosourced materials. Financial balance requires optimizing the surface areas of housing and common areas, and pooling heating and air conditioning installations, when the project allows it.
Wood frame and biosourced insulation make up most of the two additional floors of 44, rue de l’Amiral-Mouchez (Paris 14th).
