St Deiniol's church is located on High Street (A497), set back on its north side in a disused churchyard towards the centre of the town, close to the junction with Lon Ednyfed. It was built as a chapel of ease to the Parish Church of Saint Catherine in 1884-7 to designs of Douglas and Fordham, architects, of Chester, but was never finished. It was intended to serve as an English Church for the growing resort.
It was built in a Geometric Gothic style of dark grey granite rubble with red sandstone dressings. Its plan was cruciform, consisting of a six-bay nave, passage aisles, a three-bay chancel with sanctuary, south transept chapel opposite north transept for organ and vestry, and a south porch opposite a polygonal baptistry. It had a short spire with low, broad, broaches. Battered buttresses and bellcote give a dynamism to the building.
The original interior had a boarded wagon roof supported by false hammer-beam trusses and wind braces, and an arcade of continuous low pointed arches (without capitals) to corridor aisles, and recessed clerestory windows above. Also, a boarded and ribbed chancel ceiling with arched braced trusses. A west tower was planned but never built, marked by a blocked arch in the west wall.
The church was closed for worship in 1988 and was converted into residential flats in 1994.

Sources:
Cadw Listing database
Haslam et al., The Buildings of Wales: Gwynedd (2009), p.350

David Leighton, RCAHMW, 7 November 2014