Failed lead flashing is behind a huge share of roof leaks — and it's the one that's hardest to spot. How it fails, what it costs, and why patching it doesn't work.
If a roofer has been out twice and the leak is still there, flashing is the first place to look. It's the most common cause of leaks that appear inside while the tiles above look perfectly fine.
What Flashing Is
Lead flashing is the metal dressed around the joins where the roof meets something else — a chimney, a wall, a dormer, a skylight, a valley. It's the seal at the most vulnerable point on any roof, and it takes the full force of weather on its own.
How It Fails
- Cracking — lead work-hardens with movement over decades and finally splits along a fold
- Lifting — where it was never dressed far enough into the mortar joint, water gets behind it
- Mortar loss — the pointing holding the flashing into the chimney or wall washes out, and the flashings come free
- Oxidation and pinholes on very old leadwork, especially on Victorian and Edwardian homes across Rochester and Chatham
Why It's So Hard To Find
Water entering behind flashing can run along a rafter for metres before it drops through the ceiling. The damp patch is rarely above the problem. That's why a survey has to include the loft — looking at where water is actually tracking, not just where it comes out.
Why Patching Doesn't Work
Squirting sealant or bitumen over a failed flashing is a stopgap measured in months, not years. Lead repairs properly by re-dressing the existing lead where possible, or renewing the section and tucking it correctly into a raked-out joint. On period properties in Medway this needs matching traditional bossing and welding — the wrong technique on old leadwork causes more damage than it fixes.
Chimney and flashing repairs from as low as £100 depending on access. Free survey with photographs of exactly where the water is getting in.
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Costs and timings in this article are guides for Medway and Kent properties. Every roof is different — a survey is the only way to get an accurate figure.