Building these twenty social housing units located in the commune of Cornebarrieu, near the city of Toulouse, on a budget that could not go beyond 1,150 euros per square meter, presented an excellent opportunity to demonstrate that construction with stone walls is still a feasible option. The last hundred kilometers of the Earth’s crust are composed of stone, so the material is virtually inexhaustible. Preparing it for use in construction is inexpensive because it simply has to be extracted in the quarry, transported, and brought to the actual site. Moreover, its energy behavior is optimal. On these premises it was decided that the building should be raised with loadbearing walls 40 centimeters thick, and using limestone ashlar blocks laid on lime mortar. Developed on the basis of its corresponding on-site lifesize drawing, each ashlar was the object of a specific detail: lintels and embrasures for openings; protective cornices for walls, which double as lanes for large doors; and special stones perforated to accommodate pipes for the draining of rainwater. The result is a massive envelope, perforated with windows protected against the sun, which works as a passive regulator of temperature and humidity inside. All this thanks to the density, heating capacity, and transmission coefficient of stone, which give it an excellent thermal inertia.