The church of St Thomas is located in the village of Bylchau, on the north-east slopes of Mynydd Hiraethog.
The church was built in the Early English style to plans of G.G.Scott and consecrated on 27 October 1857. Built in dark rock-faced stone with slate roofs, it consists of chancel and nave under a single roof, gabled north porch, corbelled west bell-gable and lean-to south (?) vestry. Inside, the nave and chancel are separated by a timber arch, marked externally by buttressing. The church is lit through cusped lancets. Contemporary stained glass in the east window is by Wailes.
Sources:
E.Hubbard, Buildings of Wales: Clwyd (1986), p.114.
D.R.Thomas, History of the Diocese of St Asaph vol.2 (1911), p.7-8.
Google Street View, August 2009.

David Leighton, RCAHMW, 25 September 2015