The baths building is of the type designed by the Miners' Welfare Committee architects following the Miners' Welfare Act of 1926 which permitted costs of construction of baths to be raised from wages and coal royalties. Baths were managed by trustees appointed from the colliery company and workforce. The Miners' Welfare Committee Architects' Department designed baths across Britain and developed a house style influenced by the Modern Movement. Such baths typically contained showers and heated lockers, a canteen and medical centre. The Crumlin baths is typical of early designs and probably dates from the late 1920s.

The building is a long single-storey structure with two linked parallel gabled ranges to the North, and a central plenum tower for the water tanks and hot air system, and a boilerhouse and chimney to the South. It is built from brown brick, which is now mostly painted, and has a corrugated and concrete roof. The two gabled sections formerly contained the lockers - clean on one side and dirty on the other - and are seven bays long, with a flat roofed area between, which formerly contained the showers. The entrance block to the front has a flat roof and parapet and there is a tower to the rear. The boilerhouse which formerly contained boilers for heating water for the showers and air for the drying lockers, is adjacent to the South. This is a flat roofed block with parapet and an attached slightly tapered chimney with a blue brick decoration in a simple Art Deco style: a thin vertical panel on each side and a pierced capping band, with three metal-framed windows to the side.

Source:- Cadw listed buildings, NJR 29/09/2008