51 Ballymongan Road, Ballymongan, Castlederg, Co Tyrone, BT81 7HF

51 Ballymongan Road is a single-storey, three structural bay thatched house with whitened walls, dating from approximately 1820–1839. It stands on the east-facing slope of Ballymongan, approached by a short lane north-west of the road from Killeter towards Meenafergus, close to the border with the Republic of Ireland, about three miles south-west of Killeter. The building sits slightly below road level.

This is a direct entry house of traditional vernacular form, constructed in roughly plastered stone over layers of cow dung, with whitened walls. The base is finished with a black painted plinth. The central section is thatched between parapet gables with cement fillets. The timber sheeted entrance is a half door, protected by a windbreak porch over which the thatched covering extends. The porch is flanked on either side by a vertically sliding window with plain sashes and curved sash stops. The sill on the right (north) is of traditional depth, whilst that on the left (south) is narrow.

The historic layout remains unchanged. An outbuilding has been incorporated on the south side and successfully integrated to provide bedroom and bathroom accommodation. This section is roofed with stonewold slates terminating in a concrete parapet, with seamless aluminium gutters and plastic downpipes. Two windows light the front of this section: a small window towards the thatched part and a larger window towards the left (south). Both have plain sashes with curved sash stops and narrow sills. Identical fenestration is provided at the rear. A single casement window of three horizontal panes lights the kitchen to the north of the outshot. To the north of the thatched section, a fuel store is roofed with corrugated iron, with seamless aluminium guttering at the front and pressed metal at the rear; the door is of timber plank construction with plastic downpipes.

Opposite the house on the east stand outbuildings in two roof levels, constructed of whitened stone with corrugated iron coverings and timber plank doors, one of stable type.

The fireplace has been altered, but the rare double bed unit has been retained. Modifications to the windows have not adversely affected the building's appearance.

A building matching the present structure appears on the Ordnance Survey map of 1833–34 and in all subsequent maps. The building was not recorded in the first valuation of approximately 1834. The reference map accompanying the second valuation of approximately 1858, together with subsequent post-1863 annual valuation revisions, is missing from the Public Record Office of Northern Ireland, preventing access to later 19th-century valuation details.

By 1992, when listed, the building's condition had deteriorated. A conservation scheme by Gerry Agnew, involving re-thatching, strengthening the roof timbers, repairing the chimneys and stonework, was completed in 1994. Further re-thatching was carried out by Gerry Agnew in 1999.

This building is of special interest as a rare survivor of a once common type of Irish vernacular dwelling.