Capel Seion was built in 1895, but in the twentieth century its congregation amalgamated with the English Marine Calvinist Methodists and the Welsh Calvinist Methodist Capel Mawr, and the site was re-named Capel Y Traeth. It is Classical in style, with a smooth rendered gable end facade, with render and terracotta dressings. The side and rear elevations are roughcast. The roof is of slate with red ridge crest tiles. The front facade has two storeys and six bays, with narrow round-arched windows. A central porch occupies three bays, with a wider gable carried on cast iron columns. The side bays each have paired round arched windows, while the upper storey has four round arched windows with sidelights, below a single impost band.A parapret with a terracotta ballustrade surrounds the outer bays.
Inside the chapel is a horseshoe gallery mounted upon cast iron columns, with decorative wooden panels. There is an organ gallery to the north east of the chapel. Below the box pews are similarly arranged in a horseshoe shape with two aisles. The pulpit and set fawr are highly decorated. Above is an enriched plaster ceiling with central rosettes in a panel of fretted woodwork, surrounded by further panels and rosettes.

Source: Cadw Listed Building Record
RCAHMW Inventory Documents

K Steele, RCAHMW, 20 February 2009