St Monica's War Memorial Cathedral follows the basic form of the original basilica model of the early Latin churches. Bishop Cahill requested the architect to design the cathedral with arches as a major design element; however, Ian Ferrier has said that he found it a challenge to reconcile the use of arches whilst designing in the modernist idiom. He developed a system of reinforced concrete arches along either side of the cathedral, which house leadlight windows surmounting doors to side verandahs. The side arches were designed in concert with a vaulted ceiling; however, due to cost constraints, the vaulted ceiling was eliminated and a flat soffit erected in its place which internally obscures the top of the arch. The cathedral was constructed with a reinforced concrete frame, with inner and outer skins of brickwork, and the side verandahs were designed to allow the side doors to be left open, particularly during the wet season, to allow cross ventilation. The original design included transepts, which were deleted due to cost constraints; however, a section of the southern transept was retained as a side chapel. The original design of the cathedral also called for more extensive use of marble, particularly to the floors of the nave and sanctuary. The architect's original intention for the leadlight windows was to eventually house stained glass when funds permitted, but in the interim to use gold and light blue glass as per his design for the Sisters of Mercy St Bernard's College, Herberton. However, Bishop Cahill did not like the colour blue and requested that the windows be constructed with a field of burgundy red glass with an amber border. It was not until the glass was being installed that the enormous impact of the vast areas of burgundy red glass began to be felt. However, as the glass had been paid for and delivered to site, there was no option but to install it.
