The Building Conservation Directory 2021

52 T H E B U I L D I N G C O N S E R VAT I O N D I R E C T O R Y 2 0 2 1 C AT H E D R A L C O MM U N I C AT I O N S SCAFFOLDING BRIDGET DRAKE-WILKES S CAFFOLDING IS often an essential tool to gain access to areas of a building or structure, yet where a historic building is concerned it must be used with caution. It is necessary to have detailed plans and scaffolding designs in place as erecting such a structure could harm the historic fabric of a building, such as when a scaffold is secured with drilled fixings. This type of damage increases incrementally each time a scaffold is erected. Considerations for this can often be overlooked when plans for works are temporary, but it is vital that the necessary steps are taken to avoid any maltreatment of the historic structure. Aspects such as selecting a scaffolding system, listed building consent, planning for electrical earthing, and scaffolding tie types to use should be carefully planned before any works commence. PRINCIPAL TYPES Tubular and proprietary system scaffolds are commonly used to provide access for the inspection, maintenance and repair of historic buildings. The vast majority of tube and fitting scaffolds do not require bespoke design other than an assessment of site-specific wind loading. These types of scaffold are generally referred to as ‘TG20 compliant’, which is a reference to guidance produced by the National Access and Scaffolding one or two scaffold boards inside the standards adjacent to the building face. There are also proprietary system scaffolds developed by individual manufacturers with standardised components and proprietary design guidance. Historic buildings most commonly require the following types of scaffolding: • temporary propping or shoring • temporary enclosures • scaffold remaining in situ for an extended period • external free-standing towers (including buttressing to reduce a scaffold’s height to width ratio) • birdcage (internal access) scaffolds that are heavily loaded or free-standing with a slender height to width ratio • suspended scaffolds or cantilever scaffolds • aluminium scaffolds. Where works cannot start immediately, a temporary enclosure, propping or shoring may be necessary to prevent further deterioration or even collapse of the building fabric. This can provide protection or stabilisation until a full programme of repairs is implemented. If a temporary enclosure is envisaged, the performance requirements should be stated in outline in the pre-construction information. If there are heavy or awkward items to be installed under an enclosure, gantry beams may need to be incorporated into the scaffold for moving them. A birdcage scaffold providing access for the repair of roof timbers from the inside: no fixings to the existing structure are needed because of the width. (All photos copyright Historic England) Another form of independent scaffolding erected around Walsall Cenotaph for masonry cleaning and restoration work Confederation (NASC). Scaffolds which do not conform to this guidance require site-specific analysis and design. The most common arrangement is tied independent scaffold. This consists of a double row of standards (vertical members), each parallel to the building, and rules regarding loading, bracing and tie spacing must be adhered to. The inner row is set as close to the building as possible or offset to accommodate