Seion Welsh Independent Chapel was first built in 1814/5, but later rebuilt to the design of Richard Owen of Liverpool in 1878. It was further modified in 1903 and after 1908. It is built on a tighly enclosed urban site, and is in the Italianate Classical style, with two storeys plus a basement. The gable end facade is of snecked rubble masonry with painted freestone dressings; the central bay is articulated by paired giant pilasters with composite caps and by a crowning triangular pediment and has paired central entrances below a tripartite round-headed window. The outer bays each have rusticated facades, with a single plain sash window to the ground floor and an arch-headed window with tracery to the upper storey.
Within the chapel has a three-sided panelled and bracketed gallery mounted upon cast-iron plain Ionic columns. Above, the ceiling is plastered, with coving and panelling to the central nave, with acanthus ornamented roses in each bay. Transverse ribs cut through the dentil cornice and are carried on Corinthian corbel shafts. Behind the platform and set fawr with balustraded parapets rests a full height organ case.

Source: Cadw Listed Building Record
RCAHMW Inventory Documents

K Steele, RCAHMW, 16 November 2009