Is your copper fabric flashing compatible?

Copper fabric flashing has a history of great longevity, puncture resistance, and tear resistance. These facts have been known for over 80 years, since York invented copper fabric flashing.

 

Why did York stop making their copper fabric flashing with asphalt? Compatibility and adhesion!

 

Asphalt coated copper fabric flashing is coated with Mica dust, which keeps the asphalt from sticking to itself while the product is in a roll.  The issue with Mica dust is:

  • Air barriers, sealants, and polyurethane spray foam insulation systems need a clean substrate to adhere to.
  • No air barrier systems have approved the use of asphaltic copper fabric flashing with their system.

 

In 1935 asphalt was originally used for copper fabric because it was a readily available and inexpensive. The design of the cavity wall has changed dramatically over the past decades adding more components to the wall systems.  The drawbacks to using asphaltic copper fabric flashing are:

  • Asphalts from different sources should always be tested for compatibility with each other, since there are many components that make up asphalt.
  • Oil in bituminous products are known to migrate and cause incompatibility reactions. An Oliensis test (ASTM D-1370) should be conducted on any project that includes asphaltic copper fabric flashing.
  • Asphaltic copper fabric flashing is not to be held beyond the face of the brick, since the asphalt will emulsify and stain the brick veneer. A drip edge is recommended, which increases components and cost to the project.
  • Temperature:
    • Cold: asphalt does not form well on the jobsite below temperatures of 40°-50°F
    • Heat: asphalt starts to soften and change chemical composition around 84°F, on hot days in the summer, the sun can cause it to run/stain.
  • Solvent based mastic is the only sealant used for sealing asphalt coated copper fabric flashing.
    • Mastic is 60 – 80% petroleum/asphalt and 20 – 40% of mineral spirits (solvent)
      • Solvents are not recommended to be in contact with polystyrene foam insulation (Think of a foam cup and gasoline…not a good combination).

 

Only two manufacturers remain selling the asphaltic copper fabric flashing and most manufacturers have moved to the non-asphaltic copper fabric flashings.  Benefits of non-asphaltic copper fabric flashing include:

  • Compatible with all known air and vapor barrier systems
  • Compatible with all polyurethane spray foam insulation systems
  • Compatible with most cavity wall sealants
  • Clean working surface
  • Less laps due to longer rolls
  • Can be run to the exterior face of the brick, so no drip edges are needed
  • Flexible down to -25°F and is stable to 275°F
  • Same life of the wall longevity as the asphaltic copper fabric flashing

 

Non-asphaltic copper fabric flashings are manufactured by:

  • York Manufacturing Inc. : Multi-Flash 500/ Flash-Vent
  • STS Coatings: Wall Guardian CF-500/ VF-1000
  • Wire-Bond: Copper Seal
  • Advanced Building Products: Sealtite 2000
  • Mortar Net, Inc.: Total Flash Copper Fabric