Pen y Fal Hospital Chapel was built c.1883, and therefore contemporary with the closure of the chapel in the main building of the Joint County Lunatic Asylum. It is not shown on the 1st edition OS map surveyed in 1879. It may have been designed by architects Giles and Gough who did the alterations and additions to the main buildings, but the design shows nothing of the Jacobethan character that characterises their work. The chapel is constructed of snecked, bull-nosed, red sandstone rubble masonry with freestone bands and window dressings It has a tall, slate roof with red tile cresting. It is built in a Gothic style and is cruciform in plan with 4-bay nave, transepts, apsidal chancel and an octagonal fleche at the crossing. The west front has a 5-light, Geometric window with a taller central light which has three quatrefoils in the head. This is over a flat roofed, full width porch with twin gable arched entrances, with single light windows on either side. The nave has lancet windows with stepped buttresses between. There are four-light transept windows of similar character to that at the west end. The main entrance is now in the north transept, and an added gabled porch for this cuts into the base of the window above. There is a cylindrical chimney stack to the south transept. The east end is semi octagonal, with gables over 2-light ogee windows. The fleche has an open traceried bellcote and a crocketed top.

RCAHMW August 2011