A late 18th century house with a slate tablet above the central entrance inscribed P / TM / 1780. It was extended to the rear by the addition of a gabled wing in the late 20th century. The house is not marked on the Tithe Map of the parish, made in 1840, however the map was not comprehensively annotated and not all buildings were shown. Gwyndy Bach was built on land then owned by William Wynne Sparrow Esq, part of the extensive farmstead centred around the farm and coaching house at nearby Gwyndy. The 1841 Census Returns record numerous occupants of Gwyndy Bach, which then may have included other cottages close by the house, including Owen Williams, Miller, and his extended family, as well as 2 other families, among whom were 4 joiners and 2 agricultural labourers.

An 18th century, 2 storey house, with a single storey wing in line to left (S) and a lean-to to the right. It is built of rubble masonry with slate sills to the windows, and with a modern roof of small slates, with gable stacks with dripstones and capping. It has recessed, horned sash windows, with the ground floor having 12-pane windows, and the first floor having smaller, 4-pane windows set directly under the eaves. The central entrance has a shallow rectangular overlight and a slate tablet above inscribed P / TM / 1780.

The single storey wing is advanced from the main elevation and has a blocked doorway to the front. In the north wall is a small-paned, replacement, casement window. The lean-to has a boarded door to the left.

The gabled extension to the rear is 2-storey, the ground floor with slate cladding and a wide doorway to right, the first floor with timber cladding and large modern window. There is a lower, single storey, block to the rear built of rubble masonry with a slate roof and a single modern window.
(Source; CAdw listing database) S Fielding RCAHMW 02/10/2006