Llandaff Sub-Control Centre

The Llandaff Sub-Control Centre is a single-storey rectangular building oriented on an east-west axis. Constructed from brick and concrete, it features a projecting plinth and a flat roof with roof-level vents, but is otherwise unadorned. The entrance is located at the west end, where there is a slight projection; the doorway is recessed and fitted with a modern security door.

Upon entering, there is a timber door that leads into a small ante-room, with a messenger waiting room to the right and a corridor straight ahead that runs the entire length of the building. Rooms are situated on either side of the corridor, with operational rooms on the south side and support and plant rooms on the north side.

From the messenger waiting room, the operational rooms include a message room equipped with timber acoustic cubicles, followed by a large control room that is currently empty. The support and plant rooms consist of a plant room housing generating equipment, ventilation plant, controls, and intact switchgear installations. There are also men's and women's WCs, with urinals and toilets still in place, a small kitchen featuring a Belfast sink, boiler, and cupboards, a storeroom that was originally a ladies' dormitory, a dormitory fitted with steel-framed double bunks, and a liaison officer's room at the end.

Throughout the building, four-panel timber doors remain, along with various telephones and original wall fixtures, including air ventilation ducts and light switches. The operational rooms are connected by intercommunicating hatches in the dividing walls to facilitate communication between adjacent spaces.