Tyle Crwn-isaf is a former down hill sited sub-medieval long-house, which was rebuilt in the early seventeenth century, when a two-storey, two-unit cross-wing was added across the upper end. The down-hill facade retains a large gable window on the first floor, indicative of its former status as a hall with a floor above. The ceiling-beams to the house are all similar with `ogee' stops to the chamfers. The present entry provides easy access to the two-unit cross-wing via the hall. A former external doorway, blocked by a window at the rear below the kitchen/hall fireplace, probably indicates the position of the former long-house's cross-passage entry. Its front entrance position cannot be defined, as there is a later cart opening opposite the rear door. The cattle part of the long-house was altered in the mid nineteenth century with new ceiling-beams and roof timbers. The front west wall has been rebuilt at a slightly different angle.

Internally, the house retains four chamfered and stopped timber doorways, the parlour one with an arched head piece, provides access to an extended first-floor stair projection. In the kitchen there is a lateral projecting stone stair to the east, with a timber doorway giving access to the rooms over the hall. The hall/kitchen had its front wall rebuilt in the mid-nineteenth century, its ceiling-beam stops indicating the position of a wider wall. Similarly the fireplace and cross-wall appear to have been rebuilt in the mid -nineteenth century. There is a small later doorway in this wall leading to the cow-house, also providing access to loft stairs, probably for servant accommodation.

The two-unit cross-wing is reached from the hall/kitchen up a step through a timber framed chamfered doorway into a parlour or later kitchen. The room has what appears to be a secondary fireplace with a later timber lintel and iron-range forming a back-to-back arrangement with the parlour. It had a wide splayed window in the south wall, now part blocked with a reused early doorway leading to a later pantry. There is a similar window with a massive deep timber lintel in the east wall. The parlour is entered through a timber-framed, chamfered doorway into a room with two splayed windows to its north front, a blocked fireplace and framed arched doorway to the rear stair projection. This projection was probably similar to that in the hall/kitchen, but has been extended later with a timber stair.

The cow-house part was not measured, but retained its original west wall, while the east wall has brick arches to openings.

G.A. Ward, RCAHMW, 24 May 2007.