Is your copper fabric flashing compatible?
Copper fabric flashing has great longevity, puncture resistance and tear resistance, which are facts that have been known for over the 70 years since York invented copper fabric flashing in 1935.
Why did York stop making their copper fabric flashing with asphalt? Compatibility!
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, so the downside is:
*Air barriers and polyurethane spray foam insulation systems need a clean substrate to adhere to. No air barrier systems, to the best of our knowledge, have been approved the use of asphaltic copper fabric flashing with their system.
*Sealants need a clean substrate and the Mica dust diminishes the adherence.
*Weight: a roll of asphaltic copper fabric flashing is heavy due to having Mica dust coating both sides of it; causing shorter rolls, which means more lap joints.
Asphalt was originally used for copper fabric flashing in 1935 because it was a readily available and inexpensive adhesive. The building envelope has dramatically evolved in this time and the drawbacks to using asphalt are:
*Asphalts from different sources should always be tested for compatibility with each other, since there are many components that make up asphalt.
Refer to CSI article:
*Oil in bituminous products are known to migrate and/or cause incompatibility reactions. An oliensis test (ASTM D-1370) should be conducted on any project that includes asphaltic copper fabric flashing.
Many architects are not comfortable requiring the Asphaltic CFF beyond the face of the brick, since the asphalt will emulsify and stain the brick veneer. A drip edge is often recommended, which increases components and cost to the project.
*Cold: asphalt does not form on the jobsite well below 40-50 degrees
*Heat: asphalt starts to soften and change chemical composition at 80 degrees, so hot days in the summer it is difficult to work with.
Mastic is the recommended sealant for 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 boards: either expanded or extruded.
*Think of a foam cup and gasoline…not a good combination
Non-asphaltic copper fabric flashings are:
• Compatible with all known air and vapor barrier systems,
• Compatible with all polyurethane spray foam insulation systems and common construction sealants
• Clean working surface
• 60% of the weight of asphaltic copper fabric, so the rolls are longer for less lap joints
• Can be run to the exterior face of the brick, so no drip edges are needed
• Flexible down to -25 degrees F and is stable to 275 degrees F
• Approved for use with all known cavity wall sealants and construction materials
Non-asphaltic copper fabric flashings are manufactured by:
• York Manufacturing Inc. : Multi-Flash 500/ Flash-Vent