Plas Tan-yr-allt

The central entrance hall has a quarter-turn stair with renewed fretwork C17 style balusters and moulded newel. The L-hand room retains a mural depicting the Triumph of Neptune, but at the time of inspection it was concealed for its protection behind plasterboard. In the upper storey the landing and a small dressing room above the entrance have segmental plaster vaults. The R-hand room has a shallow quadripartite plaster vault and the L-hand room a shallow cambered plaster vault. In the rear of the main house the earlier building retains 2 collar beam trusses, superimposed on one of which are later principals at higher level, indicating that an original farm building has been heightened.

A late Georgian 2-storey villa comprising a main house near square in plan and incorporating an older building at the rear, and a later wing with service building set back on the L (W) side. Of blocks of quarried stone laid in regular courses, painted light blue. The main house has a hipped slate roof on projecting eaves and stone stack behind to the R. The 4-window front overlooks Tremadog, Traeth Mawr and Porthmadog and has a lean-to veranda with slate roof on iron posts, most of which are replacements, wrapped around the sides. The central recessed half-glazed door has Gothic glazing bars, under a fluted panel in place of a former overlight. On the L side is an added late C19 canted bay window with French doors. On the R side are French doors. The upper storey has 2-light casement windows.

The R (E) end wall has a similar canted bay window with French doors, below a 2-light casement in the upper storey. The veranda is infilled with a boarded and glazed screen on the L side. Further R is the gable end of the earlier building, which has lower eaves than the main house. It has an added lean-to in the lower storey with a wide 4-light window and half-glazed door at the R end. Above it an early C20 4-light window under a deep bracketed hood. The short L (W) return wall of the main house, in front of the service wing, has a replacement window in the lower storey and 2-light casement window above, to the L of which is an external brick stack.

Set back to the L is the 2-storey 4-bay service wing, under a hipped roof of graded slates on projecting eaves, and stone end stacks. The upper storey has 2-light casements similar to the main house. The lower storey has a lean-to veranda on rustic timber posts. The entrance R of centre has a half-glazed panel door under a 3-pane overlight. To the L are 12-pane hornless sash windows. To the R is a brick lean-to inside the veranda, with modern casement windows. Part of a former coursed stone garden wall abuts at the L end, beyond which is a lower 2-storey 2-window extension, formerly housing more service rooms, of whitened coursed rubble stone under a hipped roof. In the lower storey is a half-glazed boarded door and a link to a formerly detached and restored small stone outbuilding. The upper storey has two 2-light casements.

At the rear is the original gabled building, of scribed roughcast, slate roof and stone stack to the R. Its central hipped half-glazed porch has a half-glazed door, to the R and L of which are wooden cross windows. Further R a similar 3-light mullioned and transomed window and further L a replacement window in an earlier opening. Above the entrance is a 2-light casement under a gable. This and a gabled 3-light casement window to its L have inserted vases in the gables. Further R is a 12-pane sash window turned on its side to slide horizontally.

The 4-bay service wing projects behind the main house. It has a fielded-panel door to the L of centre under an overlight, flanked by 12-pane hornless sash windows and with a shorter 16-pane hornless sash window to the R end. In the upper storey are 2-light casement windows similar to the front, but the centre-R window is blind. Return walls have similar windows. The extension of the wing has a 2-light window upper L, two 2-light windows in the lower storey and a lean-to against the end wall.