Juan Casellas was a young woodcarver with his own business in Barcelona when he came to the attention of Bishop Fulgentius Torres. Torres invited him to come to New Norcia to help in the work of decorating the buildings of the town. He arrived with his wife, Catalina, in 1907.

Apart from a period of two years in Perth, Casellas spent the rest of his relatively short life living and working in New Norcia.
He produced two altars for the monastery, three for the Church and one in each of the colleges.

In addition to ecclesiastical furniture, he made domestic furniture including a suite for the Abbot's bedroom at the Monastery and the encased shelving in the Monastery Library. He excelled at delicate detail such as monograms and coat-of-arms. His work also shows the influence of the Art Nouveau style which was popular in Europe around 1900.

Juan and Catalina lived in the old post office on the north end of town. They had one child, a son named Manuel. Juan died of consumption in 1921 at the age of 47 and was buried in the New Norcia cemetery.