Seion Independent Chapel was first built in 1829, on a different site and is now converted into a domestic dwelling. This was replaced in 1891 by a new chapel built in the Simple Round-Headed style with a gable entry plan. It has red brick walls with buff and vitreous brick dressings. The slate roof has red tile creasting and end finials and the round-headed window openings have windows with nineteenth century glazing bars. The entrance is via the front gable, with a porch and small round-arched doorway and wooden boarded door. There are tall flanking windows and a central plaque inscribed: "Sion Addoldy/ yr Annibynwyr/ 1891". Inside the chapel has a pannelled lobby and the main chapel has a vertically-boarded dado and painted plaster walls. The ceiling, also of painted plaster, is in two bays with two ceiling roses. The pulpit has flanking steps and is decorated with gothic motifs. There are two gas lamps on the pulpit wall, the baluster front is turned to the set fawr and the chapel has a harmonium. The late nineteenth century open-bench seats include single blocks of side seats, seven on the left hand side and six on the right hand, and a wider single block of six centre seats.

RCAHMW, December 2010