Former Lewis Merthyr Colliery fan house

Of sandstone rubble and rockfaced stone; brick and stone evasees and ducts to N; Welsh slate roof. Single main storey rectangular gabled structure of 7 bays to sides and 1 bay to gable ends. S elevation of sandstone rubble with rockfaced dressings has 4 26-paned metal framed round headed windows with voussoirs, keystone and sill and 3 similar shaped doorways, the centre flanked by pilasters; E elevation of snecked rockfaced sandstone has single blind round headed arch with voussoirs, keystone and sill between pilasters with oculus above; N has blocked windows and blocked yellow brick basement arches. Louvred ventilator to roof. To W building extended by gabled corrugated metal roof to join Trefor pitbank. To N fan chamber is a flat roofed yellow brick and stone block extending at eaves height and joined from W by sloping duct from fan drift of rubble sandstone with corrugated metal covering. Square red brick evasee attached to NE corner of fan chamber.

Open to metal framed roof; corbels on side pilaster. Brick dressings to windows. Area which would have housed fan engine converted to classroom but 14ft (4.28m) diameter Schiele iron fan 1891 still in situ; its shaft has a pulley wheel with grooves for 10 cotton belts, the means by which power was transmitted from engine. Bearing of shaft can be seen on N exterior of building in recess under timber lintel. Interior of fan drift of yellow brick with round headed arches, some with deep brick intrados, and access passage.