Lead flashing: what it does and why it fails

Where flashing is found

Around chimney stacks, as aprons, step flashing and back gutters.

Along valleys where two roof slopes meet, and where a roof meets a wall — for example above an extension or beside a dormer.

Why it fails

Lead expands and contracts with temperature, and over decades it can split, lift at the edges or pull away from the mortar that holds it.

Frost gets into the mortar pointing that secures the flashing, and wind gets under lifted edges and makes them worse.

Poor earlier repairs — smearing sealant over a split rather than renewing the lead — usually fail quickly.

How it is repaired properly

Small splits can sometimes be repaired, but lifted or perished flashing is best renewed: new lead, correctly dressed and pointed in.

We trace where the water is actually getting in before recommending anything — the leak is not always where the damp patch appears. Quotations are free.