Lead is the best flashing material there is, and most failures are caused by how it was fitted rather than the metal itself. Here is what correct lead work looks like.
Lead moves, and that is the whole story
Lead expands and contracts significantly with temperature. Fitted in short bays it takes that movement up harmlessly at the laps. Fitted in one long strip it cannot, so the stress concentrates at a fold or a fixing and eventually tears.
Nearly every cracked flashing we cut out was too long. Cover flashings should generally be limited to about 1.5 metres per piece, and apron and gutter pieces similarly, with laps between them.
Codes and where each belongs
Lead is graded by code, which is its thickness. Code 4 is the usual minimum for soakers and simple cover flashings, code 5 for aprons, valleys and back gutters, and code 6 or higher for larger valleys and exposed positions.
Using code 3 offcuts where code 5 belongs is a false economy that shows up as splitting within a few winters. On a heritage roof the correct code is also usually what the building control officer or conservation officer expects to see.
How a proper repair is carried out
The old lead comes out, the mortar joint is raked to a clean chase at least 25mm deep, and the new lead is dressed to shape with proper tools rather than hammered flat. The upstand is turned into the chase, wedged with lead clips at close centres, and the chase is repointed.
Patination oil is applied to the finished surface to stop the white carbonate staining that otherwise runs down brick and stone in the first few months. That final step is skipped often and is very visible when it is.
Sealant smeared along the top edge of a flashing is the most common thing we remove. It holds for a winter or two, then peels away from the masonry as the lead moves, and by then the water has been running behind it unseen.
A related bodge is a cement fillet in place of lead at an abutment. Cement cannot flex, so it cracks, and the crack sits directly above the junction it was supposed to protect.
A single failed apron or short cover flashing is typically £250 to £550. A full chimney flashing set with apron, soakers, stepped cover flashings and back gutter is more often £650 to £1,400. Long abutment runs along a dormer or extension roof are priced by the metre plus access.
As always, scaffold drives the total. Our guide to chimney and lead flashing costs breaks the figures down further.
Can lead flashing be repaired rather than replaced?
A single small split in otherwise sound, correctly sized lead can be lead welded by a specialist. If the bay is too long, replacement is the only repair that lasts, because the cause is the length not the crack.
What is the white powder on my lead?
Lead carbonate, formed as new lead weathers. It is harmless but stains the masonry below, which is why patination oil is applied when the work is finished.
Is lead being replaced by modern alternatives?
Flexible flashing tapes and lead substitutes have their place, particularly where theft is a concern, but for durability and workability on a domestic roof milled lead is still the benchmark.
Does lead flashing need maintenance?
Very little. Check the pointing at the chase every few years and keep debris out of back gutters and valleys, and good lead will outlast the covering around it.
Is lead theft still a problem locally?
It happens, mostly on large runs on churches and commercial buildings rather than domestic chimneys. Where it is a genuine risk, we can discuss alternatives.
Suspect the flashing is the problem?
We will get up there, photograph what is actually happening at the junction and quote to put it right in lead, properly.
Evans Roofing & Maintenance Ltd, Witney, Oxfordshire. Call 07960 482233 for a free written quote.