Seion Welsh Baptist Chapel was built in 1849 to the design of Isaac Price of Rhymni. It was later rebuilt/modified in 1887, and further renovated in 1927-8. It appears in the 1851 Religious Census. The chapel is in the Simple Round-Headed syle, and has a square plan with a porch to the front and a vestry attached to the right. The building is rendered and whitewashed, with hood-moulding round the upper storey windows. The chapel is entered via a panelled door with fanlight over, set into the right side of the porch; to the front of the porch is a plain sash window, with raised pediment above bearing the inscription 'Seion'. To each side of the porch there is a single plain sash window. The upper level has three round-headed windows, with moulded cornice and keystone. The side elevations each have four plain sash windows, two upper and two lower. The vestry has a central double panelled door with fanlight over, with round-headed windows to either side. Above are three small round-headed windows. The roofs are of slate, hipped on the main chapel, pitched on the vestry.

Source: RCAHMW Inventory Documents

K Steele, RCAHMW, 17 February 2009