The cathedral is constructed in sandstone ashlar, with roofs of slate, other than the baptistry which is roofed in copper. The architectural style is Gothic Revival. Is plan consists of a five-bay nave with a clerestory, aisles and transepts, a two-bay chancel with aisles, side chapels, and a semi-octagonal apse. The steeple stands at the northeast corner, and the octagonal baptistry is attached to the north transept. The steeple consists of a tower with a spire rising to a height of 240 feet (73 m). The tower is in four stages that are separated by string courses, and it has a stair turret at the northwest corner. On the west side of the bottom stage of the tower is a gabled north porch, above which is a canopied niche containing a statue of St Peter, and a three-light window. On each side of the second stage is a row of six arches, the central two arches containing windows, and on each side of the third stage is a small window. The top stage contains paired bell openings, and at the corner of the parapet are pinnacles. The spire is recessed, and has three tiers of lucarnes. At the west end of the church is a doorway, above which is a five-light window containing Geometric tracery. Along the sides of the aisles are three-light windows with Decorated tracery. In the north transept is a four-light window with Geometric tracery, and the south transept contains a ten-light wheel window surrounded by ten circular windows. In the apse are three-light windows containing Decorated tracery.