Traditional lead work is still known as lead plumbing, although today it is mostly used for replacing and repairing roofs and guttering. Domestic plumbing formed a large part of a lead-worker’s job until lead water pipes were replaced by plastic ones, but it is now really only undertaken for ‘wiping’ or soldering joints on soil pipes in old buildings.
One of the earliest metals known to man, lead has been in use for at least 7,000 years. It is pliable, extremely resistant to corrosion and pollution, and can be melted down and reused. ‘Where possible, we recycle lead and return it to the same building,’ says lead plumber Jonathan Castleman. ‘Where there is none, we buy in scrap lead and melt it down, and to improve its quality, we mix it with pure lead, which now has to be imported as there are no lead mines operating in Britain anymore.’
Mr Castleman is the seventh generation to work for his family firm, Norman and Underwood, which was founded in 1825. He started as an apprentice plumber, and is now the managing director, responsible for measuring and surveying lead structures, and for advising on the best way to main-tain and repair them. The company’s lead-plumbing department employs 40 craftsmen (including apprentices), whose jobs have included the roofs of Salisbury and St Paul’s Cathedrals, Westminster Abbey and Windsor Castle, as well as many new buildings and Jerusalem’s Dome of the Rock.
Many roofing systems combine lead with other materials, including copper, stainless steel, aluminium and zinc, but the different techniques required by these hard metals also come within the scope of the traditional lead worker. Norman and Underwood works both with rolled lead (which it buys in) and sand-cast lead (which it manufactures), preferring the latter for use on old buildings. Rolled lead, which became common in the 19th century, is lead that has been milled by machine to a required thickness and mass produced. It tends to be smoother in texture, and has a bit more ‘creep’ than sand-cast lead, which is more natural looking and, it is claimed, longer lasting. A well-made sand-cast lead roof has a normal life expectancy of 200 years, although, if properly maintained, it could last at least 400.
The process of sand-casting lead has changed little since ancient times, although it is no longer done on site. The lead caster uses a long table covered with a smooth layer of sand, at one end of which hangs a crucible containing a furnace of molten lead. This is ladled into a header pan and then poured over the sand, where, controlled by the casters, it solidifies immediately to the required thickness, ranging from 2.24mm to 3.55mm (codes 5?8). ‘We can go up to code 12 (5mm) for special cases,’ says Mr Castleman. ‘You can only lay each thickness to a certain length, so the dimensions of the roof dictate thickness.’
The caster then cuts the lead into sheets, which are rolled into coils and delivered to the site. Here, a lead plumber fixes them by hand using copper cleats. Movement caused by temperature is allowed for by ensuring that the sheets are overlapped and have flexible seams, such as a traditional hollow roll, which is usual for steeper roof pitches, or a wood-cored roll for flatter structures. These days, the preferred traditional method of bossing, or working the lead into required shapes with special hand tools, is less used; instead, components are welded together with special equipment.
Lead hopper heads and rainwater pipes, often with decorative designs, are also sand cast, using moulds pressed into the sand. And there is also a certain demand for lead coffins, particularly for crypts, because they are airtight and therefore preserve the corpse.
Norman and Underwood: 0116?231 8000; www.nandu.co.uk
This article first appeared in Country Life magazine on October 26, 2006
For more on property, architecture, the arts and the countryside subscribe to Country Life magazine