Lead flashing is what stops rain getting in around chimneys, dormers, valleys and roof-to-wall junctions. When it fails, the leak usually shows up inside near the chimney breast or the side of a dormer. Here's how to spot the signs early.
How long does lead flashing last?
Code-4 or code-5 lead, correctly fitted, lasts 60–100 years. Code-3 lead and cement fillets typically need replacing within 15–25 years.
Can I just re-point over failed flashing?
No — re-pointing alone is a sticking-plaster fix that lasts a year or two. Failed flashing needs to be stripped and properly replaced.
What's the cost to replace chimney lead flashing?
Typical chimney: £450–£950 depending on access (scaffolding/tower) and chimney size. Full strip & re-flash on a complex stack: £950–£1,400.
Many older properties have cement fillets instead of proper lead flashing. The cement cracks within 10–20 years and lets water straight through.
Strip cement, fit new code-4 step flashing properly chased into the brickwork.
Lead pulls away from the wall because pointing has failed or it was never chased in deep enough.
Re-chase into brickwork at minimum 25mm depth, re-point with sand/cement or lead wedges.
Lead lengths over 1.5m crack from heat expansion. Common on long roof-to-wall junctions on extensions.
Replace with multiple shorter sections (max 1.5m each), correctly lapped.
Lead lasts 60+ years but eventually thins, becomes brittle and splits. Code-3 (thinner) lead fails first.
Strip and replace with code-4 or code-5 lead — should last another 60+ years.
White salt deposits (patination)
Cosmetic — but heavy white deposits can indicate water sitting on the lead due to a drainage issue.
Investigate why water is pooling; usually a fall or detail issue rather than the lead itself failing.
Evans Roofing & Maintenance Ltd, Witney, Oxfordshire. Call 07960 482233 for a free written quote.