Palladian and Neo-Palladian interiors universally rely on several structural components that vary very little and provide the foundations upon which the decoration and furnishings can be applied. These include:

• columns - usually the Corinthian order
• ceilings - usually trabeated and sometimes coffered
• staircases

These are not always based on Palladio’s work, nor on classical examples. Sometimes they have been adapted from other architectural styles and had Palladian features and ornamentation added to them.

Architectural treatises, such as Pain’s British Palladio|, first published in 1786, often discussed and demonstrated the rules of Palladian construction. They were extremely important in the development of Neo-Palladian| building. This plate shows plans and elevations for two varieties of Palladian staircase, one rectangular and one spiral.