 In 1736, he built a little annex to the hôtel, which had been purchased from the widow of Peyrenc de Moras by the duchesse du Maine, herself a Bourbon-Condé by birth.Jean Aubert frequented the unofficial Académie du Petit-Luxembourg that was founded in 1729 by the comte-abbé de Clermont, another member of the house of Condé, the younger brother of the builder of the stables of Chantilly.For the abbé, who was "abbé commendataire" of Chaalis, Aubert created the plans for the reconstruction of Chaalis Abbey in 1736.