Stone Work Conservation-Restoration Safe Work Method Statement

Heritage stone conservation requires a combination of traditional stonemasonry skills, specialized conservation knowledge, and understanding of heritage significance and conservation principles. Ideal qualifications include Certificate III in Stonemasonry (CPC30120) providing traditional stonemasonry trade skills in stone cutting, shaping, and installation, supplemented by specialized conservation training through courses offered by heritage authorities, professional organizations such as Australia ICOMOS, or recognized international programs such as International Centre for the Study of the Preservation and Restoration of Cultural Property (ICCROM). Many conservation stonemasons develop skills through apprenticeship with experienced conservation practitioners rather than formal education pathways. For project leadership roles, conservation architects typically hold Bachelor of Architecture plus postgraduate qualifications in heritage conservation such as Graduate Diploma in Heritage Conservation or Master of Heritage Conservation. All workers on heritage projects must hold Construction General Induction Card (White Card) plus any trade-specific licences required such as High Risk Work Licence for scaffolding if erecting access systems. Beyond formal qualifications, demonstrated experience in heritage conservation projects, understanding of Burra Charter conservation principles, knowledge of traditional materials and techniques, and ability to work under heritage consultant supervision are essential. Membership in professional organizations such as Institute of Architects, Master Builders Association Heritage section, or international bodies such as International Council on Monuments and Sites (ICOMOS) demonstrates commitment to conservation standards and professional development.

Historic buildings constructed before approximately 1900 in Australia used lime-based mortars rather than cement (Portland cement was not widely available until late 19th century and not commonly used in general construction until early 20th century). Using cement mortars for repointing or repairs in historic lime-mortared masonry is inappropriate and causes accelerated deterioration for several reasons: cement mortars are substantially harder and less permeable than lime mortars, creating differential stiffness at interfaces where softer lime-mortared stones are unable to accommodate movement causing stress concentrations that crack stones adjacent to hard cement joints; cement mortars prevent moisture vapor transmission trapping moisture within masonry and causing deterioration through freeze-thaw damage, salt crystallization, and biological growth that would not occur with breathable lime mortars; cement mortars are difficult to remove if future repairs are required, with removal often damaging adjacent historic stones, violating conservation principle of reversibility where interventions should be removable without causing harm; and visually cement mortars typically have wrong color, texture, and joint profiles appearing incongruous in historic construction. Lime mortars replicate original material properties providing compatibility in strength (weaker than stones allowing mortar to sacrifice preferentially rather than damaging stones), permeability (breathable allowing moisture vapor transmission), and flexibility (accommodating minor movement without cracking stones). They also provide reversibility as lime mortars can be removed in future without damaging historic stones. The appropriate lime type depends on exposure conditions: non-hydraulic lime (lime putty) for sheltered interior locations, natural hydraulic lime (NHL) grades 2, 3.5, or 5 for increasingly exposed conditions. Proper lime mortar specification, mixing, and application requires specialized knowledge and experience - inadequately mixed or poorly specified lime mortars perform unsatisfactorily creating false impression that cement is necessary.

Respirable crystalline silica exposure in stone conservation work requires same rigorous controls as other masonry trades despite heritage conservation context potentially creating pressure to avoid water-based methods. Primary control is wet cutting and grinding methods using continuous water flow suppressing dust at source. All stone cutting for replacement pieces must use wet masonry saws with integrated water delivery systems creating visible water suppression throughout cutting. Grinding to shape repairs requires angle grinders fitted with water-feed attachments or dust shrouds connected to Class H vacuum with HEPA filtration. Where heritage conservation requires surface cleaning that might involve abrasive methods, use wet micro-abrasive systems (such as Jos system) that use water and fine abrasive in controlled low-pressure application rather than dry abrasive blasting. For accumulated dust removal from building voids or surfaces, use HEPA-filtered vacuums rather than dry sweeping or compressed air which creates extreme exposure. Mortar raking during stone removal and repointing should use wet methods where practical or on-tool dust extraction. Even with engineering controls, provide fitted P2 or P3 respirators for all workers performing cutting, grinding, or cleaning operations, with annual fit-testing confirming adequate seal. P3 respirators (99.95% filtration) are preferred for intensive cutting or grinding operations. Implement health surveillance program including baseline lung function testing (spirometry) and chest X-rays before commencing stone conservation work, with periodic monitoring (typically every 1-2 years) detecting early silicosis enabling intervention before advanced disease develops. Heritage constraints do not override worker health protection - if heritage consultant proposes methods creating excessive silica exposure, engage them in collaborative problem-solving identifying alternative approaches achieving conservation outcomes while protecting workers. SafeWork authorities have been clear that heritage significance does not justify compromising worker health, with enforcement action taken against conservation projects with inadequate dust controls.

Temporary support requirements depend on stone location, structural function, and deterioration extent. For lintels spanning openings (doorways, windows) that carry structural loads from masonry above, install adjustable acrow props or steel needles beneath lintel before commencing removal, transferring loads to adjacent jamb stones or walls. Props should be positioned on adequate bearing pads distributing loads to prevent point loading damage. For arch stones, particular care is required as arches rely on compression forces through all stones with center keystone being critical. Install temporary timber formwork or proprietary arch centring beneath arch during keystone or surrounding stone removal. Formwork should be designed to carry full arch and superimposed loads. For large deteriorated wall sections, install scaffold tube cages or frames surrounding area acting as containment if unexpected collapse occurs during removal, and providing temporary lateral restraint. For cornices, parapets, or decorative elements that have detached from backing structure, install ties, straps, or temporary framing preventing collapse during access and inspection. All temporary support systems should be designed by structural engineer experienced in heritage structures who can assess loading, deterioration effects on remaining capacity, and appropriate support configuration. Temporary supports must remain in place not only during removal of deteriorated stones but also throughout installation of replacement stones and mortar curing until new work achieves adequate strength - for lime mortars this may be 4-12 weeks depending on mortar type and exposure. Premature removal of temporary supports has caused collapse of newly repaired work with stones falling and creating injury risk. Document temporary support installation including photographs and certification by engineer where required. Never commence stone removal without adequate temporary supports in place - the short time saving is not worth catastrophic risk if deteriorated stones prove weaker than assessed or adjacent stones are disturbed causing progressive collapse.

Heritage conservation principles embodied in Burra Charter and applied by Australian heritage authorities strongly prefer traditional materials and techniques that are compatible with original construction and reversible if future treatment is required. However, this does not mean worker safety can be compromised for heritage authenticity. The key is collaborative problem-solving with heritage consultants identifying approaches that achieve both conservation outcomes and worker protection. For example, if dry cutting is proposed for stone shaping to avoid introducing moisture, engage heritage consultant to understand concerns and propose alternative controls such as using minimal water application that dries quickly, cutting stones offsite where water introduction is not problematic, or allowing adequate drying time before installation. Most heritage consultants recognize that wet cutting with proper technique does not cause significant moisture-related issues and is essential for worker protection. For chemical consolidants and treatments, modern formulations including ethyl silicate or acrylic consolidants are considered acceptable in conservation practice as they are reversible with appropriate solvents and provide better performance than historic materials. Respiratory protection, ventilation requirements, and chemical handling controls remain identical to any chemical use regardless of conservation context. For access scaffolding, modern tube-and-clip or proprietary systems are essential for fall protection despite being anachronistic - they can be designed to minimize visual impact and prevent physical damage while providing required safety. For temporary supports during stone removal, modern adjustable props and steel needles are appropriate and superior to historic timber shoring techniques. If heritage consultant proposes methods creating unacceptable risk, your duty under WHS legislation is clear - identify the risk, attempt to find alternative approaches, but ultimately refuse to proceed if safety cannot be assured. Document these discussions and decisions. Contact SafeWork authority for guidance if agreement cannot be reached. Heritage significance does not override legal duties to protect worker health and safety.