What Materials Are Used in Roof Flashing?

Roof Flashing: What materials are used?

Roof flashing is key to protecting your home. Learning your options can help you determine which option is right for your home. Roof flashing requires the use of three different types of materials.

1. Basic Flashing material – see below
2. Expansion joints for metal flashing material, and fasteners for other kinds of flashing materials
3. Flashing (roof) cement

1.Basic Flashing Material

These are the prime materials needed for roof flashing. They may be made of:

• Metal
• Plastic
• Rubber
• Impregnated Paper
• Recent synthesized industrial materials

Metal

Metal flashing materials are very popular and metals used for roof flashing include:

• Copper and lead-coated copper
• Aluminum
• Galvanized and stainless steel
• Zinc Alloy
• Lead

Copper is the most durable of the metals, it has a resource-heavy manufacturing process and so is the more expensive than most other metals used in flashing. Aluminum is next in line in terms of durability. It is easier to manufacture, and so is relatively inexpensive. Further down is galvanized steel, which is much cheaper but not as durable as available alternatives. Lead is a favorite for specific types of roof flashing because of its ductility (ability to bend easily). However, lead is associated with certain health risks that predate increased adoption.

There are other metallic alloys like Galvalume— a product similar to galvanized steel—which have not gained much traction but are effective roof flashing materials.

Plastic

Plastics (chiefly PVC) are  sometimes used in conjunction with vinyl siding.

Rubber

Rubber-based roof flashing materials include:

• Rubberized asphalt
• Butyl rubber
• Acrylic

Asphalt Impregnated Paper

Rubber

Ice and Water Barrier

Usually these basic materials are available in pre-defined forms and sizes to make installation easier, yet it is possible to get large rolls or pieces that can be cut into custom shapes and sizes.

Note that rubber, impregnated paper, and ice and water barrier membranes are sometimes used in addition to a metal flashing.

2. Expansion Joints

Expansion joints are necessary to prevent deformation of the metal flashing materials that may result from contractions and expansions. For metal roof flashing, the choice of material used for expansion joints is very important because of galvanic corrosion.

Galvanic corrosion is a chemical reaction that results in the pairing of two metals that should not be used together. This chemical reaction will occur, as an example, when lead or copper are used with zinc, aluminum or coated steel.

3. Flashing Cement

Flashing cement is an adhesive solution applied to secure flashing to other roofing materials, including other pieces of flashing.