Penllwyn Calvinistic Methodist Chapel, chapel house and schoolroom including railings and gates

The Penllwyn Calvinistic Methodist Chapel, along with its associated chapel house and schoolroom, features iron railings and gates. The chapel itself dates to the late 18th century, with later additions and alterations. It is constructed of unpainted render with stucco dressings, capped by a slate roof with paired brackets to the eaves. The front elevation is a long, five-bay design, displaying four arched windows and a central door. Angle quoins are present. The windows are small-paned and incorporate radiating bars to their heads, each with a moulded arched hood, keystone, and a string course with keystones at the impost level. A similar moulded arch and keystone above the string course frames a date plaque bearing the inscription "Penllwyn a adeiladwyd yn y flwyddyn MDCCCL" along with the dates 1790 and 1821, and the name J James. The central doorway has a moulded arched head, radiating-bar fanlight, and panelled double doors. A section of rubble stone forms the right-hand end wall, featuring two arched windows with stone voussoirs, and a boarded loft door also with stone voussoirs. Brackets are positioned under the overhanging gable verge. The rear elevation mirrors the front, with four windows.

The chapel house is set back to the left, displaying a lower two-storey, two-window range, bracketed eaves, and a brick stack on the left end. It has nine-pane sashes on the upper floor and twelve-pane sashes on the ground floor to the left, with a board door and overlight on the right. Behind the chapel house is a schoolroom, situated higher on a bank. This long range exhibits brick-framed side windows added in the later 19th century, with three-light windows containing top-lights on the west side, and two square sixteen-pane sashes with cambered brick heads on the east side, likely dating from the mid-19th century.

Attached to the front of the chapel are iron railings set upon a low rubble stone wall rebuilt in the 20th century. The railings feature knob-topped rails, and double gates incorporating bands of half-circles at the midpoint and bottom rail.

The interior of the chapel is broad and lacks galleries, accommodating seating for approximately 500 people. Entry is centrally located on one side, with a pulpit positioned on the end wall to the left. The chapel contains numbered box pews in four blocks, arranged in ten steps up to the right; the side blocks are narrow, while the block along the wall opposite the entry remains on a flat surface. A cross-aisle from the central entry divides the two central blocks on the flat from the raked pews. Two blocks of inward-facing pews flank the pulpit on the end wall. The pews are panelled with moulded surrounds to the prominent end and front panels, and the rear pews have ramped top rails. A later lobby, partially glazed with double half-glazed doors, is situated behind the main entrance door. A heavy carved wood pulpit features turned balusters to the steps on each side, ramped stair rails, turned newels with ball finials, and low balustrades over panels. The pulpit front projects with canted panelled sides and features two horizontal panels between panelled piers, supported by heavy console brackets carrying a bookrest. Behind the pulpit is a simple plaster arch with paired console brackets to the capitals and a moulded arch. A "set fawr" is similar to the pulpit, with a bench facing the pulpit featuring a baluster back and turned newels, the sides simply being attached benches to the original box pews, with later 19th-century newel posts affixed to the ends. The plain plaster ceiling incorporates a moulded cornice, a small acanthus rose, and plain roundels.