Needing a way to get up to the choir loft the nuns prayed for St. Joseph's intercession for nine straight days. On the day after their novena ended a shabby-looking stranger appeared at their door. He told the nuns he would build them a staircase but that he needed total privacy and locked himself in the chapel for three months. He used a small number of primitive tools including a square, a saw and some warm water and constructed a spiral staircase entirely of non-native wood. The identity of the carpenter is not known for as soon as the staircase was finally finished he was gone. Many witnesses, upon seeing the staircase, feel it was constructed by St. Joseph himself, as a miraculous occurrence.

The resulting staircase is an impressive work of carpentry. It ascends twenty feet, making two complete revolutions up to the choir loft without the use of nails or apparent center support. It has been surmised that the central spiral of the staircase is narrow enough to serve as a central beam. Nonetheless there was no attachment unto any wall or pole in the original stairway, although in 1887 -- 10 years after it was built -- a railing was added and the outer spiral was fastened to an adjacent pillar. Instead of metal nails, the staircase was constructed using dowels or wooden pegs.