Historically, many building interiors were plastered with non-hydraulic lime, sand and hair (sometimes gauged with gypsum) or, alternatively, clay, a lime binder and reinforcement such as straw, concealed under a lime skim. Such plasters are applied directly to solid backings, such as masonry or cob, or flexible supports, including timber laths or reed.
... supports, including timber laths or reed. Lime or clay plaster can have a more pleasing character as well as offer better internal ... and components
Lime or clay plaster ceilings ...