On separation of the Church and State in1905, the State made an inventory of all church properties. The town Les Pavillons-sous-Bois was not concerned by this: there were no places of worship. Worshippers from Pavillons-sous-Bois went to Sunday mass at the church Saint-Louis in le Raincy or in Bondy.
In 1908, Abbott Alfonsi settled in the town which was a mostly a working and socialist municipality. Initially, the Abbott opened an oratory in the dining room of a small house. After that, he ordered the construction of a small chapel. Two years later, with the help of worshippers in the town and despite an anticlerical majority, the abbot laid the first stone of a church. The ceremony was tempestuous and the crowds gathered did not hide their hostility. While Abbott Alfonsi’s worshippers chanted hymns, a crowd of people turned up shouting "A bas la calotte – off with the skullcap" and singing The Internationale. Undaunted, the Abbott continued his blessing and the future parishioners their religious songs. And the church, placed under the patronage of Notre-Dame-de-Lourdes, came to light. It was inaugurated by the Archbishop of Paris, Monseigneur Amette, on September, 17th, 1911.
Construction work was complicated. The land was swampy; the edifice had to be constructed on oak stilts. Contrary to the habitual orientation to the East (toward Jerusalem), the building was oriented toward the South. The porch contained the doorway entrance. The nave consisted of two identical rows, separated by a large transept barely prominent. The square formed by their crossing was covered by a dome. The windows were made in the seventies by a young artist from Pavillons-sous-Bois.