The short answer
Lead is used on roofs because it is soft enough to be shaped by hand into any junction, it is waterproof, it does not rust or rot, and a well-fitted piece can last for many decades. Tiles and slates cover the flat expanses of a roof, but they cannot seal an internal corner or a joint against a wall. Lead can, and it moves with the building without tearing. That combination is why roofers still reach for it.
It can be shaped to fit
The awkward parts of a roof are the places where a surface changes direction: a chimney that rises through the slope, a wall that rises above it, a valley where two slopes meet, a dormer cheek, a pipe. Each of these has an odd shape and none is standard. Lead can be dressed into the corner with a wooden tool and a mallet, stretched round a curve and folded over an edge, all on site, without special equipment.
Stiff metals and plastics need pre-formed pieces, and they come in set angles. Lead, in contrast, takes the shape of whatever it is beaten into. That is why you find it in nearly every flashing detail on a pitched roof, including the tight corners around a chimney. Our page on what roofing leadwork is goes through the full list of places it is used.
It lasts
Lead forms a thin, hard oxide layer within months, and that grey skin protects the metal underneath. It does not rust like steel, rot like timber or become brittle in sunlight like many plastics. Properly fixed lead on a church or a country house can stay in place for generations, which is why so much historic roofing still carries the original metal.
Lifespan is not guaranteed by the material alone. It depends on thickness, fixing and movement allowance, which you can explore in our answer on how long lead flashing lasts.
It handles movement and weather
Buildings shift a little as they warm, cool and settle, and roofs expand and contract more than the walls. Lead is ductile, so it flexes without cracking when it is correctly detailed with clips, laps and rolls. It is also heavy enough to sit tight against a surface without fluttering in wind, which matters on exposed sites.
It sheds water well. A smooth metal surface carries rain off quickly, and with laps cut to the right depth the water cannot find a way behind. That is a big advantage over mortar fillets and sealants, which crack as the building moves.
It is easy to repair
Another practical advantage is that damaged lead can be mended on site. A split can be closed with a weld, a worn section can be cut out and replaced, and a loose edge can be re-wedged into the wall. Rigid materials usually have to be swapped whole. That repairability keeps the cost of ownership down on a roof that is looked after, and is one reason lead has stayed in use for so long.
It suits old and new buildings
On period and listed homes, lead is often the expected material, and a conservation officer is unlikely to question it. On new builds, it is used where a neat finish is wanted, such as roof junctions on extensions. It also recycles well: scrap lead has a value and can be melted down and reused, which makes it one of the more sustainable roofing metals.
The places lead is most often found
Look at almost any older roof and you will find lead in the same few places. Chimneys have a lead apron at the front, step flashings up the sides and a back gutter behind. Valleys between two slopes carry a lead channel. Dormer windows have lead cheeks and a lead roof or flashing above. Bay windows, porches and canopies often have a lead-covered roof. Pipes and vents through a slate roof use a lead slate to seal the opening.
All of those are junctions, where a flat covering meets a wall or another slope. That is the common thread: lead is not used to cover large areas of a house, but to join the large areas together.
How thickness is chosen
Lead sheet is made in a range of thicknesses, each given a code number. Thin sheet suits small flashings with little exposure, while heavier codes go on valleys, gutters and flat roofs that carry more water or take more wear. Choosing the right code is a judgement on the length of the run, the exposure and the budget. Too thin and it fatigues early, and too thick and the cost and the weight rise for no benefit. Our guide on lead codes explained sets this out.
Where it falls short
The material has drawbacks, including cost, theft risk and handling safety, and we cover them frankly in a separate answer on the problems with lead roofing. There are alternatives where lead is not the right choice, and we will tell you if one suits your roof better. Everything else we do with lead is listed under lead roofing services in Basingstoke.
Every roof is different. A free survey with photos settles it for yours.
Get a free survey