Former Lewis Merthyr Colliery lamproom and fan house

The former Lewis Merthyr Colliery lamproom and fan house is a Grade II* building constructed of rubble sandstone with prominent brick dressings and a Welsh slate roof. It is a single-storey, rectangular gabled structure with four bays on the sides and two at the gable ends. The south elevation features two tiers of semicircular windows with multipane radial glazing, brick surrounds, and concrete sills, along with a round-headed doorway on the left side (west) that includes a fanlight and double plank doors. The gable ends on the east and west have a single round window at the apex and two semicircular windows below. The north elevation has full-height windows with multipane metal-framed glazing and a second door, while the basement includes cambered arched windows and a door.

Attached to the northwest is the fan house, built of stone and brick, which houses a metal casing for the fan and features part chamfered brick evasee with a corbelled top. Inside the lamproom, the space is open to the metal-framed roof, with arcading above the lower bays. A travelling crane by Herbert Morris of Loughborough is present. Steps lead down to a quarry-tiled ground floor, which is partially divided by metal partitions into offices and secure storage areas, with adjacent racks for recharging lamps. Steps also lead down to the fan house, which contains a 1950s electric motor by David Brown and Sons and a Scirocco fan within its metal casing, although the fan was not accessible during the inspection in January 1996.