The single greatest identifying characteristic of St. Joseph's Church is the majestic copper-hued dome, which rises above the sanctuary.  Unique in Florida and the tallest structure in Mandarin, it invites the community to worship. The dome speaks of unity, integrity and primary center of liturgy.  Topped by a simple cross, the dome represents  Christ's dominion over all. Rising 70 feet above the sanctuary floor, the dome is 60 feet wide at its base and 32 feet tall. It was custom designed and created specifically for St. Joseph's Church by the Monolithic Dome Institute, a Texas-based company. The column-free, clear-span dome allows maximum use of space and optimal quality of view.

Constructed in place by spraying polyurethane foam inside a lined, steel frame, the dome received additional steel reinforcement.  A special mixture of concrete was then sprayed onto the dome to form the shell.  Throughout the entire process, special blower fans were utilized to inflate the liner and help set the materials.  The exterior of the dome was covered with a metal plating.

The dome is accented by 12 stained glass windows - four different images of a dove in flight repeated three times - to represent the Holy Spirit eternally soaring high above the congregation. The beauty and simplicity of the windows create an atmosphere of reverence in the sanctuary below.  The dome windows are original creations by Jim Piercey of J. Piercey Studios of Orlando.