The estate’s history stretches back to at least 1713, when Peter Aylward came into possession of the property through his marriage to Elizabeth Butler, whose family had previously held the land from their seat at nearby Paulstown Castle. Aylward built or remodelled a house here that year, creating what appears to have been a fairly typical early Georgian structure with a recessed centre flanked by projecting end bays.

The castle’s current Gothic appearance owes much to renovations carried out sometime before 1828, when the house underwent a dramatic transformation. The end bays were crowned with crenellations, and one was raised to resemble a medieval tower, complete with a slight base batter that gives it an authentic defensive appearance. The National Inventory of Architectural Heritage suggests this ‘tower’ might incorporate fabric from around 1600, noting its battlemented parapets, cross blind apertures, and slit style windows; all classic features of a medieval fortification. The five bay, two storey house now sports dormer attics and rendered walls, with the tower section featuring battlemented corner piers and crow stepped gables with cut stone coping.

However, the medieval credentials of Shankill Castle remain questionable. No castle or fortified house appears on the detailed Down Survey maps of 1655 to 1656, which meticulously recorded such structures across Ireland. Architectural historian Mark Bence Jones suggests the tower may have been deliberately raised during the early 19th century castellations to create the illusion of medieval origins, a common practice during the Gothic Revival period when landowners sought to add romantic antiquity to their estates. Without further archaeological evidence, the true age of the tower remains an intriguing puzzle, though its 19th century Gothic makeover successfully created the impression of ancient fortification that its creators clearly desired.