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How to survey and assess fibrous and traditional plasterwork

This article discusses the identification, survey, and assessment of fibrous and traditional lime-based plasterwork in buildings, particularly in light of recent guidance following the collapse of a decorative plaster ceiling at the Apollo Theatre in Westminster in 2013. The Association of British Theatre Technicians (ABTT) published guidance in 2015, followed by Historic England's interim guidance in 2019, to assist conservation professionals and building managers. Fibrous plasterwork, a lighter, quicker, and cheaper alternative to traditional lime-based plaster, gained popularity in the mid-to late 19th century. While often associated with public buildings, its presence is increasingly noted in private houses from the late 19th and early 20th centuries, necessitating surveyors' ability to identify its type and appraise defect risks. The primary method of fixing fibrous plasterwork, known as wadding, involves hessian ties soaked in plaster of Paris. Post-Apollo Theatre collapse investigations revealed that wad ties are vulnerable to environmental conditions, dampness, damage from interventions, and additional loading. Historic England identifies wadding as a significant risk to fibrous plaster integrity. The ABTT guidance, largely incorporated into Historic England's publication, emphasizes regular inspections for fibrous plaster ceilings, especially those supported by unreinforced hessian wads, which are considered deleterious and likely to require reinforcement to prevent collapse. If areas cannot be inspected, the use of unreinforced wads should be assumed. The guidance from both ABTT and Historic England recommends that competent structural engineers inspect supporting structures, and competent plaster inspectors assess plaster parts. Inspections should occur from both above and below, examining surrounding fabric for water ingress and structural movement. A baseline survey is crucial to document construction, including all supports, to inform repairs and future asset management. This may involve adding or replacing support ties, removing debris, reducing loads, consolidation, or replacing ceiling sections. Baseline surveys also dictate the timing of subsequent inspections, with regular checks for changes like cracking and staining required between major inspections. The article extends these principles to traditional lime-based plasterwork, which was more common in British buildings until the mid-20th century and shares similar vulnerabilities. Traditional decorative ceilings, applied to timber laths, form plaster nibs or rivets for mechanical keying. These can be damaged by loading, alterations, insulation upgrades, or vibrations. Inspection should cover timber laths, ties, connections, and surrounding fabric for water ingress. A close inspection of the underside of the ceiling is necessary to record defects such as cracks, detachment, and surface disruption. Accurate recording of construction methods and defects informs repairs and monitoring. Retention and repair of traditional lime-based plasterwork is the preferred approach, especially in significant buildings, with wholesale replacement being a last resort. Guidance from English Heritage, Historic Environment Scotland, and Cadw should be followed for repairs. Key recommendations for working with plaster include identifying plaster type, assessing fixing methods, evaluating surrounding fabric, adopting a conservative repair approach in significant buildings, encouraging training for non-conservation professionals, and implementing regular inspections based on baseline surveys. #FibrousPlasterwork #TraditionalPlasterwork #BuildingConservation #HeritageBuildings #BuildingSurveying #CeilingCollapse #HistoricEngland #MaintenanceAndRepair #PlasterInspection #FibrousPlasterwork #TraditionalPlasterwork #BuildingConservation #HeritageBuildings #BuildingSurveying #CeilingCollapse #HistoricEngland #MaintenanceAndRepair #PlasterInspection

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