Three main factors that would have an impact on the architectural design would be skill of the workers, missionaries personal taste, and standard religious patterns. The floor plan of a church would usually be consistent with the standard architectural design of the missionary's faith. Local missionaries had the ability to modify the design or structure to their liking. Money, the skill level of the workers, along with the preferences of the aboriginal and missionaries, determined the size and detail of the church. ("Mission Church Architecture on the Industrial Frontier," 13.)

The nave, sanctuary, and sacristy were the three standard rooms in a Roman Catholic floor plan. (Ibid., 12) The nave, largest room in the church, has benches (pews) with knee rests. Stairs would separate the nave and chancel sections of the church. The chancel room is where the priest conducts his service. Priests stored their religious clothing in the sacristy room, which is connected, next to the chancel.

In comparison with other churches St. Mary's can be considered an average building. The church is a wooden structure supported by rocks (originally) with single plate and stained glass windows. The tower with the bell is the most dominant feature of the church. The roof of the church has wooden shingles along with cove sided walls. Living facilities, for the traveling priest, are located on the second level at the back of the church. The smaller building connected to the back of the church is the outhouse.

The reason most churches were built using wood is because "stone , brick, and iron were much too expensive". (Ibid., 13) Most churches, including log structures, were built using the 'balloon frame' technique. The 'balloon frame' style of building, developed in the 1830's, saved time and money. Individuals such as G.E. Woodward believed that it would only take two people to raise a 'balloon frame' structure in comparison to "a traditional, heavy-timber building of equal size, (which) required the labour of twenty men". (Ibid.)

Even though the majority of aboriginal peoples started out as unskilled builders missionaries soon realized that their "faculty for imitating and picking up practical knowledge is wonderful; anything (he sees) done (he) will reproduce without trouble." (Ibid.) Local Band members who had woodworking skills became an important asset because they had the ability to make the interior furnishings for their and other churches. (Ibid.)