Dalquharran Castle was not the first example of Adam's castle style in Ayrshire, nearby Culzean Castle was started in 1776. His ideas for Dalquharran began after a visit to the site in which he produced a sketch that showed a castle overlooking the old castle and the Girvan Water, a design for a mansion that was conceived as an arresting feature in the landscape.
Adam's design for the castle was finished by 1785. The plan of is a classical arrangement of central entrance hall and staircase. The wooden paneling in the hall survives, now fashionably distressed. Many rooms retain wooden lath and plaster on the walls.
The top lit stairwell contains a spiral cantilevered staircase of great elegance, even in its present degraded condition.
The servants staircase was concealed in a turret.
The south facing drawing room had magnificent views across the Girvan Water valley.
Dalquharran was four storeys high, with the east wing having an oval dining room on the ground floor while the west wing had an apse ended bedroom and dressing room. The shape of the dining room inserted into the interior by means of walls of varying thickness illustrates Adam's concern to maintain the external symmetry of the mansion. The two top floors were used for bedrooms while the room at the top of the south turret was the library, with its lost fixtures designed by Adam himself.
The basement provided the service accommodation. The blue and cream tiles indicate where the cooker used to be.