Bishop Thomas appears to have become attracted to the idea of interment of his remains within the Cathedral, and to the possibility of relocating the remains of Bishops Byrne, Dunne, O'Farrell and Norton to the same place. By 1979 plans had focused on the conversion of the Mortuary Chapel erected by Bishop Norton into a crypt. Final plans for the conversion of this space, including the installation of steel shelving with terrazzo shelves to carry up to 12 caskets, were prepared in December 1980. These drawings included plans for new panelled doors intended to secure the space and to carry the arms of deceased Bishops interred within the crypt. The plans were signed off by builders F.H. & I.H. Cunningham Pty Ltd on 12 June 1981. Stone conservation works were undertaken in 2016, with stages 1 (tower) and 2 (Keppel Street facade) completed that year. The original building was designed in a Gothic Revival style with Early English influences popular in England in the 1940s and reflecting English Catholic Liturgical practice, particularly evident in the work of renowned English architect Augustus Pugin (1812 - 1852). The Cathedral was constructed in red brick with decorative stone coursing and mouldings from local Mount Lambie sandstone. Internally the Cathedral consists of an aisled nave with round sandstone columns and Gothic arches. The timber hammer-beamed trusses spring from corbels high on the walls to support the high open roof. The aisles are low with a high level celestry and the Sanctuary and Chancel at the western end were substantially extended in the 1890s and 1960s. There are a number of fine stained glass windows from various periods. A high Nave and stained glass window above the gallery by John Hardman and Co dominate the western end. The brick and stone crenelated tower marks the original west end prior to the addition in the 1960s of a Narthex. The high spire proposed in the original drawings has yet to be completed. The exterior includes a number of finely carved stone mouldings, decorative bosses, gargoyles and carved heads to windows and doorways. After Vatican II some minor alterations also occurred to the sanctuary, altar and bishop's seat. The Cathedral was constructed in five principal phases as follows: Cathedral during 1857 61, Chancel and North Trancept in 1897, Blessed Sacrament Chapel in 1897, Sacristy in 1922, major extensions in 1962, and Altar modification in 1981.