Longevity and durability
The Romans first used Lead Sheet for a variety of building applications. The Normans extended its use to roofing. Many church and cathedral roofs used Lead and records show it has outstanding lifespan with some structures remaining functional after more than 500 years.
Rolled Lead Sheet is the only lead sheet that is manufactured to a British and European Standard. Computer control in today's rolling mills means an astonishing degree of consistency of thickness – as little as 5%.
BSEN 12588: 2006 specifies thickness tolerances and chemical composition in order to produce a consistent microstructure.
When Lead Sheet is fitted to a roof, this minimal variance in thickness means that the extent of thermal movement can be accurately predicted and the correct fixing method adopted.
Lead remains stable and impervious even in the most severe exposed conditions too. Lead Sheet has a very high resistance to atmospheric corrosion. Newly installed Lead Sheet forms a surface film of protective oxides in the form of a patina that is both strongly adhering and highly insoluble. Any low levels of corrosion products leaving the surface of the roof are extremely small and become highly diluted with rainwater. As Lead naturally binds to the soil, the combination of correctly designed roofs with gutters with drainage points plus the virtually undetectable discharge levels means that bio-availability within the eco-system is extremely limited.
The Building and Conservation Research team at English Heritage has been investigating why Lead very occasionally corrodes on the underside in old buildings.
Their conclusions are that weather variations during installation and changes to the interior of the building can have a significant effect. However, they conclude that if no unusual decay is encountered during repair, there is no need to alter the constructional form and detail of an old Lead roof.
Fortunately, where Lead is used in today's modern buildings these problems don't arise, thanks to changes in methods of roof construction, now outlined in Building Regulations and British Standards.
Finally, consider this – if the roof you specify needs replacing in the future for whatever reason, it will probably be in the time of your great, great grandchildren and even then, the Lead can be stripped off and its recycling value can contribute to the cost of the new roof – meanwhile today's so-called alternatives will have failed a century or more before!
