Lead is the oldest metal flashing material in Western building tradition. It predates copper in roofing applications and remains in use on historic buildings and in restoration work where its properties — extreme malleability, self-healing at minor abrasions, very long service life — make it the correct material. In contemporary New England roofing practice it is used primarily for valley flashing on slate roofs and for step flashing in historic restoration where lead was the original material.
Lead flashing is a dull grey, slightly blue-grey, soft to the touch. It can be bent by hand. It conforms to irregular surfaces without cracking. Over decades it develops a stable patina of lead carbonate — grey-white — that is self-protective. It does not develop the visual interest of copper patina, but it does not require it. It is a working material.
Sheet lead for roofing applications is available in several weights. For valley flashing: 4 lb lead (1/16" thick) minimum; 6 lb lead preferred for high-water-volume valleys. Lead valleys are installed as a continuous strip of sufficient width to extend 6 inches minimum onto each roof slope, with the center bend at the valley angle. Joints are lapped a minimum of 6 inches.
Lead moves significantly with temperature change — more than copper. Valley sections should not exceed 8 to 10 feet in length without an expansion provision. Lead in contact with fresh concrete or lime mortar can corrode — isolate with a bituminous tape. Documented service life in valley applications: 60 to 100 years.
Lead is historically correct for valley flashing on slate roofs in the British-influenced building tradition. It remains the correct specification for restoration work where lead was the original material, and where its extreme malleability allows it to conform to irregular historic roof surfaces that copper sheet cannot.
From roofing lead suppliers. Specify by weight: 4 lb or 6 lb sheet lead in rolls. Work with a sheet metal contractor or roofer who has lead flashing experience — lead requires different tools and technique than copper.
Six-pound sheet lead for valley flashing on slate roofs in restoration applications where lead was the original material. Maximum 10-foot sections without expansion provision. Isolated from masonry with bituminous tape. Lapped joints minimum 6 inches. This is a restoration material — for new construction, specify copper.
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