A rectangular stone keep and the main curtain wall were added by the Normans in the 12th century, under the de Turberville family.

An adjoining chapel wing with a tall east window was added to the first floor at the eastern end of the domestic range in the 15th century.

There was in the few years following Sir Lawrence Berkerolles's death much general reshuffling of property interests in Glamorgan, for example with the Stradling family.

The Gamage succession was not, however, easily achieved for in September 1412, that is to say whilst the supposed true heir the minor Thomas de la Bere was still alive, William Gamage assisted by Sir Gilbert Denys (d. 1422) of Siston, Gloucestershire, and formerly of Waterton-by-Ewenny,[6] in Coity lordship, besieged Coity for a month, trying to oust Lady Joan Verney, wife of Sir Richard Verney and daughter of Margaret de Turberville, from the Castle.

Commission to William Newport, Chivaler, Rees ap Thomas, John Organ, William Sparenore, Richard Delabere and Robert Wytney on information that Gilbert Denys, Chivaler, and William Gamedge, with no moderate multitude of armed men have gone to the castle of Coytif in Wales and besiege it and purpose to expel Joan, late the wife of Richard Vernon, Chivaler, from her possession of it, to go as quietly as they can to the castle and raise the siege, cause proclamation to be made that no one under pain of forfeiture shall besiege it, but those who pretend right and title in it shall sue according to law and custom.

Denys and Gamage ended up in the Tower of London for having taken the law into their own hands, from 19 November 1412 until 3 June 1413, being released after the death of Henry IV.

[10] During the 16th century, Coity Castle, by then owned by the Gamage family, underwent a complete remodelling of the living quarters, including the addition of a storey, new windows, and two chimney stacks.

The range of domestic apartments comprised a central first-floor hall set above a vaulted undercroft, from which it was reached by a grand spiral stair.

It was originally built and inhabited by Payn de Turbeville and his wife, the daughter of Morgan ap Meurig, in 1092.

In 1180, Sir Gilbert de Turberville, Lord of Coity, took over the castle and carried out extensive renovations.

Sir Lawrence Berkerolles occupied the castle in the late 1300s, followed by Lady Joan Verney, a childless widow, in 1411.

To access the eastern walls, visitors can take a short path down Heol yr Eglys, a side road.

The castle's ruined curtain walls on the western side enclose several remains of the internal buildings.