FGIA Analysis July/August 2021

August 20th, 2021 by Nathan Hobbs

Proving Effective: Putting the Sealing Ability of Liquid-Applied Flashing to the Test

By Rich Rinka

Flashing is a key element of proper door and window installation. It establishes water resistance continuity between the fenestration framing and the weather resistant barrier of the building envelope.

Of the various types, liquid-applied flashing is becoming more prevalent. Specifiers must select these products based on strength and durability of adhesion to their specific building envelope substrates, are all determined by laboratory testing to meet industry consensus and model code ratified acceptance criteria.

Getting it Right

To assist in this task, FGIA publishes several AAMA specifications for each type, the one for liquid-applied flashing being AAMA 714-19, Voluntary Specification for Liquid-Applied Flashing Used to Create a Water-Resistive Seal around Exterior Wall Openings in Buildings. It describes test methods (typically referencing ASTM test standards) used to simulate field conditions and specifies minimum acceptance criteria.

Basic testing consists of a peel strength adhesion test conducted on a minimum of three fully cured specimens, per ASTM C794-18, Standard Test Method for Adhesion-in-Peel of Elastomeric Joint Sealants. This basic test includes visual inspection for potential damage and is performed after exposing the samples to four different sets of simulated jobsite conditions.

Accelerated Aging with Ultraviolet (UV) Light Exposure: While liquid-applied flashing is exposed to UV light only briefly before it is covered by the exterior fa├žade, this can affect future performance. Testing is conducted after exposure to UV light from either fluorescent or xenon arc sources for prescribed periods of time.

Elevated Temperature Exposure: Direct or reflected sunlight can cause the temperature of the building envelope to greatly exceed ambient temperature, and flashing must remain stable after such exposure. Products are classified according to the level of thermal exposure they are designed to withstand as verified by testing over seven days of exposure for each classification level.

Thermal Cycling/Freeze-Thaw: Flashing must maintain adhesive strength and elastomeric flexibility through the wide ranges of thermal cycling that varies with regional climates. To confirm this, it must pass the peel and appearance tests after exposure to 10 temperature cycles, each consisting of eight hours.

Water Immersion: The flashing must pass the peel and appearance tests after immersion in lukewarm water for seven days.

Besides the peel tests, all samples are tested for:

Water Penetration Resistance around Nails or Fasteners: The cured liquid-applied flashing must maintain the water-resistive seal around fasteners where windows are attached to the wall. This testing is performed per the same method as described for self-adhering flashing in the AAMA 711 specification.

Crack Bridging Ability: A flashing product is categorized according to the maximum substrate crack width for which it maintains a seal when tested under exposure to temperature cycling.

Rich Rinka is technical manager, fenestration standards and U.S. industry affairs for the Fenestration and Glazing Industry Alliance (FGIA).
rrinka@fgiaonline.org

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