FGIA Analysis September/October 2022October 4th, 2022 by Nathan Hobbs
Sticking With Data: Testing For Liquid-Applied Flashing Ensures Long-Term Adhesion
By Aaron Blom
Flashing has the critical role of integrating a door or window with the exterior sheathing and water resistive barriers (WRB). There are four types and their performance is governed by the AAMA testing standards developed by the Fenestration and Glazing Industry Alliance (FGIA) to verify performance and compatibility in expected applications. Of these, liquid-applied flashing is common, due to its relative simplicity of application.
The testing standard for liquid-applied flashing is the recently updated AAMA 714-22, Voluntary Specification for Liquid-Applied Flashing Used to Create a Water-Resistive Seal Around Exterior Wall Openings in Buildings. This FGIA document describes test methods used to verify minimum adhesive performance after exposure to laboratory-simulated environmental conditions.
A Look at the Procedures
Testing consists of a peel strength adhesion test conducted on fully cured specimens per ASTM C794-18 (2022), Standard Test Method for Adhesion-in-Peel of Elastomeric Joint Sealants. This test evaluates strength of adhesion to each of four basic substrates: concrete masonry units, cement mortar slabs, oriented strand board and plywood, and includes a visual inspection, noting any objectionable appearance. This peel test is performed after exposing samples to the following four sets of simulated field conditions.
Accelerated Aging with Ultraviolet (UV) Light Exposure: While liquid-applied flashing may be exposed to UV light only briefly before it is covered by other materials, this exposure can affect future performance. A peel test is conducted after exposure to UV light from either fluorescent lamps or xenon arc sources for specified periods of time and using specified irradiance values.
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 and throughout the life of the building. Products are classified according to the level of thermal exposure they are tested to withstand.
Thermal Cycling/Freeze-Thaw: Flashing must maintain adhesive strength and elastomeric flexibility through a wide range of thermal cycling that varies with regional climates. To confirm this, a sample must pass an adhesion test and a visual inspection after exposure to 10 temperature cycles.
Water Immersion: The flashing must pass an adhesion test and a visual inspection after immersion in lukewarm (73°F ± 4°F) water for seven days.
In addition to the adhesion tests and visual inspections completed after simulated conditions, all samples are tested for water penetration resistance around nails or fasteners and for crack bridging ability.
A Table of 17 different building substrates is provided that may be filled out by the flashing manufacturer indicating the lowest temperature at which the
specific liquid-applied flashing product provides an acceptable adhesive bond strength to the substrate. If a product is installed at temperatures below those specified in this table, an adhesive/primer should be used per the manufacturer’s recommendation.
AAMA 714-22 will soon be available at FGIAonline.org, as are all FGIA standards.
Aaron Blom is technical training specialist for the Fenestration and Glazing Industry Alliance (FGIA).
To view the laid-in version of this article in our digital edition, CLICK HERE.