BCD SPECIAL REPORT ON HISTORIC CHURCHES 32nd ANNUAL EDITION 5 NEWS REVIEW LEAD HSE LEAD REVIEW SPARKS ALARM ACROSS ROOFING AND HERITAGE SECTORS UNDERFLOOR HEATING AT ST PAUL’S, COVENT GARDEN A fine example of cast lead ornament on the hopper of a church in Wiltshire: the skills required to conserve and repair work like this are already in short supply, and further restrictions could be catastrophic. A review by the Health and Safety Executive (HSE) has set off alarm bells across the UK construction industry. Proposals announced in June 2025 would tighten limits on workplace lead exposure, threatening the repair and conservation of historic leadwork. However it is not clear how we can reduce exposure to lead without harming historic buildings. Currently, under the Control of Lead at Work (CLAW) Regulations 2002, workers handling lead are subject to annual blood tests to monitor the amount of lead in the bloodstream, with those exceeding existing thresholds suspended from work. In 2024, over 5,000 workers across Great Britain were under medical surveillance, with 11 cases leading to suspension due to excessive blood-lead levels. HSE is now reviewing these limits with the intention of cutting them significantly. Presently, the suspension level stands at 60 µg/dl (60 micrograms per decilitre, or 0.6 milligrams of lead per litre of blood) for most people and 30 µg/dl for women of child-bearing capacity. The proposals would reduce that threshold to just 30 µg/ dl by October 2026, followed by a further tightening to 15 µg/dl by Taking experienced craftspeople out of work would make the existing skill shortages even more acute and would deter people from taking up the craft. While the health and safety of our craftspeople must always take priority, solutions are required that meet the needs of both our heritage and the people who work on them. Improved workplace practices may be part of the solution, but working on site can be challenging and both the Lead Contractors Association and Icon (the Institute for Conservation) are concerned that the higher standards proposed may not be achievable. October 2028 for most employees. For women in their child-bearing years, the levels fall to 10 and 5 µg/dl respectively. The problem is not limited to the bloodstream: lead accumulates in our bones and may be released slowly back into the bloodstream long after workplace exposure has stopped, so craftspeople with the most experience are often the most at risk. The new limits would therefore make legal compliance far more challenging for older and more experienced contractors in particular. The implications are particularly severe for the conservation of historic places of worship. Many have shallowsloped roofs covered with lead, while others have slated or tiled roofs which rely on complex lead details to keep out water, particularly at abutments. Finials and weathervanes are also often sheathed in lead, and embellished with finely turned mouldings. Ornate lead hoppers and downpipes can also be found in some of our oldest churches and cathedrals, but are now extremely rare elsewhere. And lead cames are an integral part of stained glass windows and leaded lights. Lead roofing is already under threat from lead theft and skill shortages. A new approach to underfloor heating has been developed which requires minimal intervention to timber flooring. A recent installation in St Paul’s, Covent Garden, London (designed by Inigo Jones and Grade I listed) was achieved without any significant changes to the historic fabric. It is estimated that as many as one in four churches could benefit from this approach. In the quest for low-carbon heating, the use of underfloor heating installations combined with heat pumps is increasingly common. This is because heat pumps (whether groundsource or air-source) produce hot water at a temperature that is too low for conventional radiator systems, but is ideal for underfloor heating due to the much larger surface area that is warmed. Underfloor heating also has the benefit of heating the entire congregation, rather than just those members who are close to the radiator. Where the surface is of clay tiles or stone paving laid on an earth floor, the installation of underfloor heating involves not only the removal and relaying of the surfaces, but also extensive alterations to the subfloor to ensure that the ground does not conduct the heat away. However, in roughly a quarter of all places of worship, the floors beneath the pews consists of timber floorboards on joists with a void below, as at St Paul’s Covent Garden. These are ideal for a system first developed in Canada which uses finned convectors heated by warm water. At St Paul’s, the contractor fitted a reflective breathable membrane loosely over and between the joists so that it could support a thick insulation blanket between the joists. The pipework for the heating system was then suspended between the joists on plastic tubing, and finally louvered aluminium fins were clipped on to the pipework to radiate heat and to warm the air around them. The reflective membrane helped direct heat upwards, while allowing the substrate to breathe. The top where it lapped over the joists had to be painted black so that it could not be seen through the floorboards afterwards. The historic floorboards were numbered so they could be relayed in the same position without alteration, and the whole installation was completed in just ten days. Engineers from Ultra-Fin installing an underfloor heating system between the joists at St Paul’s, Covent Garden.
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