How Long Does Lead Flashing Last?

When a cost guide states that lead flashing "can last for over 80 years", read the wording closely. It says over 80, so the figure is the floor of what a sound installation can reach. It does not say your flashing will reach it, and it is not a warranty. A guarantee on a job and the life of the metal are two different things.

Is 80 years realistic in Somerset?

It can be. Lead does not rust. Left alone it forms a dull grey skin on its surface that protects the metal beneath, which is one reason old church roofs still carry lead laid in another century. What takes a flashing out of service early is almost always something done to it, or something that happened around it, and not the weather alone.

For comparison, VM Zinc points to a BRE Environmental Product Declaration stating 100 years for zinc, and CORC says well-kept slate can last 100+ years. Lead sits in the same class of long-lived roofing materials. Our page on lead against zinc looks at how the two compare in use.

Several faults take years off a flashing, and most of them go back to the day it was fitted.

Which installation mistakes matter most?

A sheet cut thinner than its position demands wears through sooner. Royston Lead's cast-lead brochure puts Code 3 at soakers only and Codes 4 and 5 among those used for flashings, so a thin code on an exposed flashing is a poor start. Lengths cut too long crack with the daily stretch and shrink of the metal, and fixings that hold the lead too firmly make it worse. Hard sealant smeared along an edge has the same effect.

Can the roof around it cause harm?

Yes. Damp trapped under lead on a boarded surface can eat at the underside, which we cover in why a lead roof corrodes underneath. Lead also takes a battering from foot traffic, so a flashing near a flat roof that people walk across wears faster than one over a chimney that nobody visits. A flashing that is stepped on, or that carries a ladder foot every autumn when the gutters are cleared, will crease and split years before its time.

Lead asks for little. The best thing you can do is look at it once a year and keep other trades from damaging it.

What should an owner check?

Scan the flashings from the garden, using field glasses if they are to hand. You are checking for edges that have curled up, seams that have parted, sheet that sags and dark runs on the wall beneath. Indoors, a brown mark on a bedroom ceiling or beside a chimney breast points at the flashing or the masonry behind it. Our guide to the signs of failed flashing goes through what is worth worrying about.

Keep gutters and valleys clear so water does not back up behind the lead, and ask any tradesperson working on the roof to avoid walking on the flashing. A repair done early, such as re-dressing a lifted edge, is a small job. The same fault left for five winters is the reason many whole flashings are replaced, and that is a much larger one.

There is no date on a flashing that says it must come off. A birthday is no reason to renew lead that still lies flat, tight and dry. What matters is its condition, which a survey shows far better than its calendar age.

How do you know when it has reached the end?

Signs that a run is finished include hairline splits at many folds, lead that has thinned until it is almost see-through at the edges, and sheet that has crept down a slope and left gaps. Patches on patches are another sign. When a flashing has had several repairs, the sum of those repairs often costs more than a fresh run would.

Where a replacement is due, it is worth choosing the right code of lead for the position, and cutting shorter lengths that can move. Ask the roofer how much of the old lead is worth keeping. Sometimes one run beside the chimney has failed while the apron at the front is still sound, and renewing only the failed run keeps the job small. For the whole service, see our lead work page. We survey the flashing first, and you see photographs of your own lead before any price is set.