Lead Flashing Explained — Why It Matters More Than the Slates

Most roof leaks happen where the roof meets something else. That junction is leadwork.

What lead actually does

Lead forms the waterproof junction wherever a roof plane meets a wall, a chimney or another roof plane. Soakers sit under each course of slates, a stepped cover flashing is chased into the mortar joint and wedged, and aprons and back gutters handle the front and rear of a stack.

Codes and why they matter

Lead is sold by code — a thickness rating. Using too thin a code on an exposed detail means it fatigues and splits from thermal movement within a few years. Exposed Cork coastal properties want a heavier code than a sheltered inland job, and it is worth asking which one you are getting.

Why mastic fails

Sealant and self-adhesive flashband bridge a joint that moves constantly with temperature. They let go, and because they look like a repair the underlying defect goes unaddressed for years while water quietly rots the timber behind.

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