The columbarium was built in the 1930s to receive cinerary urns from the adjoining crematorium. Glyntaff was not only the first crematorium in Wales, opened in 1924, but the only crematorium in Wales until the second half of the C20. People who lived across a wide geographical area of S Wales were cremated at Glyntaff and their urns and tablets deposited in the columbarium. The building was restored in the 1990s, when doors were inserted to the central lobby.

It is a single-storey building of coursed rock-faced Pennant sandstone, with dressings and central bay of reconstituted stone, under a roof which is hipped to the front, with graded grey slates to the front slope, but with darker North Wales slates to the rear.

The front is divided into 7 unequal bays by battered buttresses and has simple pointed windows in surrounds with sunk spandrels. The central bay is beneath a coped parapet and the entrance set between pilaster strips. The four-centred doorway, with prominent keystone, has modern half-glazed doors but was originally open.

At the rear there are outer gabled bays (the R-hand, W side at a splayed angle) which both have two 4-centred arches and were added in later in the C20. Between them is a colonnade under an outshut roof, of 7 bays with 4-centred arches. Tablets are attached to the walls of the colonnade, which also has a tile floor.

The entrance lobby has a mosaic floor. Both sides have a narrow central corridor with a tile floor, and are divided into bays by pointed arches, all of plaster under a plaster ceiling. The west side has urns in niches, where the east side has commemorative tablets attached to the walls.

It is listed for its special architectural and historic interest as a rare example in Wales of a columbarium, built at the first crematorium to be opened in Wales, which retains original external character and interior detail.

Source: Cadw listing description, 2020.