Fibrous plaster is a form of decorative plasterwork composed of plaster of Paris, reinforced with layers of hessian and secured within a timber framework. It was used to imitate more expensive and time-consuming traditional lime-based, hand-modelled plaster. Although fibrous plaster is often associated with the Victorian and Edwardian theatre and music hall, it was fitted in a wide range of buildings in the UK. However, it is often unrecognised, and has been ignored in technical research and conservation guidance over recent decades. This document is guidance for conservation professionals and building managers responsible for buildings with fibrous plaster in the UK. It was prepared by Historic England in association with Historic Environment Scotland, Cadw, Welsh Government, and the Historic Environment Division of Northern Ireland. This guidance focuses on fibrous plaster ceilings, since they present a potential risk of collapse if neglected. It begins with the history of fibrous plaster, and then explains forms of deterioration, current survey standards, methods of repair and finally, management of buildings with the material.