The use of lead in building materials was common up until the late 19th century when it was found to be toxic to human health. Lead is a soft metal, very malleable and fairly durable.

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Material Properties and Uses of Lead:

Resource: Lead Facts - Natural Resources Canada

• Lead is mined all over the world and found within an ore called Galena, which also can contain silver and copper.
  
• The low melting point of lead makes it good for industrial applications
  
• In the past, lead was used for windows, flashing and as an additive to paints.
  
• Lead is still mined today and used mostly for batteries.
  

The softness and ease of forming lead made it very useful for creating flashing layers in construction - the drip edges and drainage layers around doors, windows, chimneys and roofing. It is fairly inert metal and can easily form alloys - lead coated copper roofing and trim is a common building material, prized for its longevity.

Because lead is so heavy, it was often used for counterweights in sash-type windows. Some heritage homes may have cavities within the frame of the window called "weight pockets" where lead weights were attached to thin rope that would counter the weight of wood and glass window sash as they moved up and down.