Standing immediately south of the level crossing at the south end of Barmouth Station, the signal box is a small 'type 1' design built by Dutton & Co. for the Cambrian Railways in 1890. It is a two-storey brick structure under a pitched slated roof with a cantilevered storm-porch and stairs on the north-west gable. The walls are set on a plinth and are of a red brindle brick with blue engineering brick quoins and window surrounds. Two arch-headed 12-light cast iron windows are set in the ground floor north-east (railway side) elevation, below which is a full length gap in the wall, supported by old bullhead rails, enabling the signal wires and point rodding to pass through. Above waist height and extending full length on the first floor are five timber-framed six-light windows: three fixed flanked by two horizontal sliding sashes. A central nine-light window and sliding six-light, on the railway side, are set in both the north-west and south-east walls, the gables of which are horizontally boarded. Opposite the sliding sash on the north-west elevation, a glazed timber porch protects the main door to the box and stands on a cantilevered landing from which modern stairs descend to track level. The upper panels of the main and porch doors are glazed. Directly below the main door is a vertical-boarded door giving access to the locking room. The south-west elevation is all brick with a fixed six-light window at the north end on the first floor. The pitched slate roof and the similar one over the porch have blue ridge-tiles and scalloped bargeboards with a wooden finial, consisting of a ball and elongated pyramid, at each of the three gable ends.
The original lever frame was supplied by Dutton and Co. in about 1890 and had 15 levers. After the Great Western Railway took over the Cambrian Railways in 1923, the track layout at Barmouth was extended and the current frame installed in 1924. It is a standard GWR Vertical Tappet 5-bar locking frame, with 27 levers, now made redundant by the introduction of radio signalling and automatic crossing barriers on this line.
Because it obscured the view of the level crossing approaches, the signal box was to be dismantled and re-erected on a new site diagonally across the level crossing from its present position. but instead was dismantled and rebuilt (see nprn 87035) at the west end of Glyndyfrdwy station on the Llangollen Railway, where it is in use.
Sources include: Site visit by B.A.Malaws, RCAHMW, 21 November 1989; Peter Kay, Signalling Atlas and Signal Box Directory (Third Edition), Signalling Record Society, Wallasey, 2010, p.60, 70; Network Rail, Signal Box Register (undated). For further information on the types and designs of signal boxes see: The Signalling Study Group, The Signal Box - A Pictorial History and Guide to Designs, OPC, 1986.

B.A.Malaws, RCAHMW, 11 March 2015.