Flimston Farmhouse is situated just west of a minor road running from the B4319 to Stack Rocks, on the Royal Armoured Corps Castlemartin Range. It consists of a small medieval first-floor hall-house radically extended around 1600 into a three-unit farmhouse, and further altered in the 18th and 19th centuries. The house has been disused at least since the establishment of the Army Range in 1938. It is now a roofless ruin.

The house as it survives is substantially as altered around 1600. It faces east, and consists of a room to the south which may have been a service room, followed by a through-passage, the site of a kitchen or hall and a parlour cross-wing. The cross-wing projects to the rear and the stairs are positioned in the corner between the main range and the wing. To the south there is a half-octagon extension. Masonry of the earlier parts is in local limestone rubble. The front was later rendered and the roof pitch is nearly 45 degrees.

Traces of earlier construction indicate that the house was originally a hall-house, with a solar in the north cross wing. Also there is a solar hearth and circular chimney at the north side of the cross-wing, supported on corbels internally and externally, the hearth being at a low level implying a previously lower solar floor unrelated to the chamber floor level of the centre of the house. Its bressummer is chamfered and carried on quarter-round corbels. In the gable wall of the south room is the arch of a large hearth, now blocked, with a large oven at one side and a small oven on the other, and a large square chimney.

The house has been altered by the addition of a large service room at the south end, in a masonry consisting of a mixture of random rubble and a proportion of old bricks. The gable chimney of the previous south room was re-used by blocking its arch and forming an opening into the new room. Later small rooms and a porch are at the rear of the house, mostly in brickwork. The room north of the through-passage and the lower storey of the cross-wing have been converted into a single room. This has a front-wall fireplace, the flue of which sets across diagonally to the apex of the cross-wing front gable. The walls internally are battened out and lathed for plastering. A vaulted cellar with its floor about 0.5 m below the general ground floor level was perhaps inserted in the rear of the old parlour at the north-west corner of the house as part of these alterations, and entered from beneath the staircase. There is a large external water cistern adjacent to it at the north of the building.

(Source: CADW listed buildings database, 8 December 1995).

RCAHMW, February 2011