Survey Data

Reg No




Categories of Special Interest

Architectural Archaeological Historical Social

Previous Name

Thomastown Castle

Original Use

Castle/fortified house

In Use As



1750 - 1755


293029, 298835

Date Recorded


Date Updated



Attached six-bay three-storey house, dated 1754. Attached at south to tower house, built c. 1400, burnt and rebuilt 1923. Recently renovated. Three-stage tower buttressed at west corner, crenellated parapet. Extended to south to designs by William Caldbeck, 1858, consisting of four-bay two-storey block, coursed rubble walling, machicolated turret to west corner, crenellated parapet. Entrance door at tower. Range of outbuildings to west. Pitched slate roof, replacement moulded cast-iron gutters, square downpipes, rendered chimneystacks. Lime-washed roughcast render walling to keep, smooth rendered to east. Square-headed window openings, limestone sills, containing nine-over-nine original painted timber sliding sash windows to ground floor, nine-over-nine to first, three-over-six to third floor, replacement timber sliding sash windows. Fenestration at castle keep consists of pointed arch window openings, cut limestone surrounds, sills, containing replacement timber casement windows, with inward-opening Gothic overlights. Tudor arched door opening at stepped recess, containing pointed arch, timber Y-tracery overlight above timber and glazed multi-pane double doors with sidelights. Situated in large estate, ornamental gardens and canals; range of single- and two-storey outbuildings, one in use as interpretive centre. Date plaque at east chimneystack reads "2004 Cob" 1754 Thomas Tennison".


Knock Abbey is an amalgamation of two fascinating structures - a medieval tower keep and an elegant Georgian house with added Victorian embellishments. Recently renovated, it was originally owned by the Tennison family and for more than two hundred years was the home of the O'Brien family. Now open to the public for its fine restored gardens, it is full of fascination and the texture of centuries.