Archaeological excavation has found: a chapel at the west end of the south bailey; the hall with its adjoining kitchen, pantry and buttery to the east; storehouses ranged around a kitchen yard accessible from the main gate to the north of the hall; a range of large private chambers (or 'revealing chambers' i.e. audience chambers) above a wardrobe and other storerooms to the west of the hall, which dates to 1321–1383 when the castle became part of the Duchy of Lancaster's estate); and a stone-built gatehouse at the south end of the bridge, the upper room of which can be identified as the Queen's chamber in building accounts (occupied by Duchess Eleanor de Bohun of Gloucester).
The completion of these buildings has been dated to the late 14th century and are attributed to the de Bohuns and Thomas of Woodstock, 1st Duke of Gloucester.
The keep's great hall has also been located, whilst other ranges are thought to represent 'en suite' accommodation, each with their own fireplace and privy.
This could be because it was replaced in function; evidence of facility duplication exists with late-medieval halls present in both the keep and the south bailey.
The final renovation of the keep was carried out on the orders of Margaret of Anjou in 1458–1459, where the keep is referred to as a "tower" and was mainly built from the timber of at least 29 oaks, finished in flint, and later brick, facades.