What are the material options for roof flashing?
Short answer. The common roof flashing materials are aluminum, galvanized or prepainted steel, copper and lead, plus self-adhered membranes and rubber collars for specific spots. Aluminum and galvanized steel handle most Georgia shingle roofs, copper lasts the longest and costs the most, and the right choice depends on what the flashing touches and how long it needs to last.
The main metals
- Aluminum: light, easy to bend, rust free and available prefinished in colors. It is the most common step flashing and drip edge on Georgia homes. Its weak spot is masonry: bare aluminum corrodes when it sits against wet mortar or concrete, so it needs a coating or a different metal there.
- Galvanized steel: stiffer and more dent resistant. The IRC sets a minimum thickness for metal flashing of 0.019 inch, roughly 26 gauge galvanized. Cut edges can rust over the years.
- Prepainted steel: galvanized or Galvalume steel with a baked finish, often used for chimney counterflashing, valleys and trim that should match the roof.
- Copper: can outlast the house, weathers from bright to brown to green, and is soldered at corners. It costs several times more than aluminum and its runoff can stain brick and siding.
- Lead: soft enough to dress over brick and around pipes. You see it on older chimneys and as lead pipe jacks, which squirrels sometimes chew.
- Stainless steel: a good fit near salt air on the Georgia coast, less common inland.
Non-metal options
- Self-adhered membranes such as ice and water shield go under the metal in valleys, around skylights and at walls as a second line of defense, not as the exposed flashing.
- EPDM and silicone collars seal vent pipes in pipe boots.
- Vinyl flashing is made for siding and windows and does not belong in exposed roof flashing that sits in the sun all day.
The rule that matters most
Keep dissimilar metals apart. Copper touching aluminum or galvanized steel causes galvanic corrosion, and copper runoff can eat galvanized gutters below it. Use fasteners of the same or a compatible metal. Learn more in roof flashing explained and chimney leaks and crickets.