Specifying and installing flashing around exterior wall openings

by arslan_ahmed | August 11, 2023 8:00 pm

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By Aaron Blom

A weathertight building enclosure is critical when it comes to preventing air leakage and water penetration. It also significantly impacts energy efficiency, indoor air quality (IAQ), and occupant comfort. Therefore, properly specifying and detailing the transitions between fenestration products and the surrounding wall conditions is extremely important.

Flashing is what enables the fenestration product to be integrated with the exterior facing material, sheathing, and the water-resistive barrier (WRB) to ensure the integrity of the drainage plane and prevent unintended water penetration.

To help designers specify and detail the correct flashing products, the Fenestration and Glazing Industry Alliance (FGIA) recently updated two flashing standards: AAMA 711, Specification for Self-Adhering Flashing Used for Installation of Exterior Wall Fenestration Products and AAMA 714, Specification for Liquid Applied Flashing Used to Create a Water-Resistive Seal Around Exterior Wall Openings in Buildings.

Self-adhering flashing

In addition to providing the minimum performance requirements of self-adhering flashing for common exterior fenestration products, AAMA 711 offers a method for determining the flashing product’s minimum width and evaluating environmental factors when installing the flashing under typical field conditions.

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Applicable for new construction as well as replacement installations, this standard provides guidance on properly evaluating, selecting, and installing flashing for durable adhesion around the perimeter of exterior fenestration systems. Due to the importance of proper adhesion, testing of these products for adhesion to specific substrates is included. However, AAMA 711 does not address chemical compatibility, and this should be verified by the flashing manufacturer. AAMA 713, Voluntary Test Method to Determine Chemical Compatibility of Sealants and Self-Adhered Flexible Flashings, could be used to assess the chemical compatibility of self-adhering flashing with liquid applied sealants.

Before reviewing the test requirements and installation guidance provided in this standard, it is important to better define what qualifies as self-adhering flashing. These products are flexible facing materials coated completely or partially on at least one side with an adhesive material and are not dependent on mechanical fasteners for attachment.

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 Testing requirements

AAMA 711 provides testing requirements for the following performance characteristics:

• Breaking strength and elongation, previously referred to as “tensile strength” in the 2020 edition of AAMA 711. Both values are tested to a modified ASTM D3759/D3759M-05 (2019), Standard Test Method for Breaking Strength and Elongation of Pressure-Sensitive Tape. After testing, samples are measured by percent elongation to break.
• Water penetration resistance around fasteners. The flashing is adhered to oriented strand board (OSB), plywood, or treated gypsum board. Next, two fasteners, a galvanized roofing nail and a zinc-plated #8 pan head wood screw, are driven through a slotted vinyl shim, through the self-adhering flexible flashing and into the substrate. An open-ended watertight cylinder encircles the area and is filled with water and another container is placed under the assembly being tested. After the test period, if water is found in the bottom container, on the fastener shanks, or on the side or underside of the substrate, the test is reported as a failure. This test is performed both before and after thermal cycling.
• Peel adhesion. The 90-degree peel adhesion test must be performed according to ASTM D3330/D3330M-04(2018), Standard Test Method for Peel Adhesion of Pressure-Sensitive Tape’s Method F
  and AAMA 711 requires this testing for adhesion to OSB, aluminum, vinyl, and plywood. However, this test method can also be used to test adhesion
  to other substrates.
• Accelerated aging with ultraviolet (UV) light exposure. A specimen of self-adhering flashing that has been adhered to anodized aluminum is exposed to a light source per ASTM G154-23, Standard Practice for Operating Fluorescent Ultraviolet (UV) Lamp Apparatus for Exposure of Materials and G155-21, Standard Practice for Operating Xenon Arc Lamp Apparatus for Exposure of Materials. After exposure, the specimen must pass a peel adhesion test per ASTM D3330/D3330M.
• Elevated temperature exposure. A specimen consisting of self-adhering flashing applied to anodized aluminum is exposed to an elevated temperature for seven days. After exposure, the specimen is re-conditioned to standard temperature and a peel adhesion test is performed per ASTM D3330/D3330M.
• Thermal cycling. A specimen is exposed to a high temperature for eight hours, followed by a low temperature for 16 hours. This cycle is repeated
  10 times and after cycling, the specimen must pass a peel adhesion test per ASTM D3330/D3330M.
• Cold temperature pliability. This test is performed per ASTM D1970/D1970M, C734-15(2019), Standard Test Method for Low-Temperature Flexibility of Latex Sealant After Artificial Weathering, or C765-97(2015), Standard Test Method for Low-Temperature Flexibility of Performed Tape Sealants and should reveal no cracking or loss of adhesion to the panel.
• Adhesion of self-adhering flashing after water immersion. A peel adhesion test is performed per ASTM D3330/D3330M over one half the bonded length of a specimen and then the specimen is immersed in water for seven days. After immersion, a second peel adhesion test is performed. Adhesion levels are examined and any apparent swelling or change in appearance or contour is noted.
• Peel resistance. This test method is used to determine the resistance of self-adhering flashing to peeling from itself. This procedure is detailed in Annex A of AAMA 711.

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Throughout the testing process, any objectionable appearance such as wrinkling, distortion, blistering, delamination, expansion, shrinkage, or warpage of the self-adhering flashing facing material or adhesive layer must be noted.

Installation considerations

To ensure the flashing will perform as intended, it must be installed correctly. Proper installation is critical for performance and the flashing manufacturer’s installation guidelines should be carefully followed.

First, the flashing should be suitable for the regional climate, installation conditions, and expected long-term environmental exposure. Flashing installation should always follow the standard sequencing of components (commonly referred to as “shiplap” or “weatherboard fashion”) as addressed in ASTM E2112-23, Standard Practice for Installation of Exterior Windows, Doors and Skylights.

The flashing should extend a minimum of 50.8 mm (2 in.) beyond the critical interface and the minimum flashing width should be 76.2 mm (3 in.). This is based on using a window with an integral mounting flange as the baseline example incorporating a 25.4 mm (1 in.) mounting flange with a 50.8 mm (2 in.) minimum adhesion onto the wall substrate. In all cases, care must be taken to allow enough width for good adhesion and potential field installation errors.

To ensure adequate performance, the use of a clean, dry substrate surface is highly recommended. If the flashing comes in contact with different building surfaces (sheathing, WRB, concrete block, etc.), care must be taken to ensure full adhesion to all surfaces.

Installers should anticipate that temperature, moisture content, and surface cleanliness will impact adhesion. Further, certain types of sheathing materials present special challenges; therefore, the flashing manufacturer should be consulted for recommendations on adhering to specific substrates.

The following are important considerations for common sheathing/substrate types:

• OSB possesses a highly variable surface that is often not well bonded and, therefore, provides an inconsistent surface for adhesion. A primer is often needed to ensure adequate adhesion to OSB.
• Fiberglass-coated gypsum board contains a loosely bonded fiberglass mesh laminated to gypsum board. Due to delamination of the fibers, self-adhering flashing typically does not achieve adequate adhesion unless the mesh is adhesively bonded using a primer.
• Concrete block surfaces are irregular, coarse, porous, and often contain debris. Also, waterproofing coatings applied to the block can interfere with adhesion. Consequently, a primer is recommended unless otherwise specified.
• Metal substrates should be clean and dry with residual oily coatings removed to promote proper adhesion.

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Since the outdoor temperature at the time of installation can affect performance and adhesion levels, manufacturer-provided installation temperature ranges should be followed. If the installer must work outside of the recommended range, the flashing manufacturer must be consulted.

Many manufacturers recommend primers compatible with their products and specify how they should be used. For less-than-ideal conditions such as very low temperatures, dusty conditions, or rough surfaces, primers are an effective way to enhance the adhesion of self-adhering flashing.

Bubbles, wrinkles, and blisters all increase the risk of water intrusion. Many manufacturers recommend using rollers to help installers avoid these application inconsistencies.

The release liner backing should be removed immediately prior to installation to avoid contamination of the adhesive surface and loss of its properties. As best practice, the number of penetrations through the flashing should be minimized.

Self-adhering flashing products can also be used as sill pans to divert incidental moisture that enters the rough opening cavity to the exterior drainage plane. In this situation, it is possible that standing water can collect on the self-adhering product. Care must be taken to ensure proper damming at the jambs and interior portion of the sill (rear upturned leg) to direct the standing water to the exterior. Sloping the sill to the exterior is recommended. Installers should ensure the sill pan is integrated continuously with the WRB and that penetrations, seams, or other discontinuities do not allow water intrusion through the sill pan.

Liquid-applied flashing

Like all FGIA published standards, AAMA 714 was developed in an open and consensus process. It establishes the minimum performance requirements for liquid-applied flashing, which is used to create water-resistive seals around exterior wall openings in buildings. This includes fenestration products such as windows, doors, and skylights as well as other through-wall penetrations.

Specifiers can use this information to evaluate and select the appropriate liquid-applied flashing materials for their project, based on three different levels of heat exposure classification.

AAMA 714 recognizes that certain local codes and regulations may take precedence. All products must meet regulatory volatile organic compound (VOC) content requirements and other environmental considerations. In addition, proper personal protection equipment (PPE) should be used when handling liquid applied flashing.

Prior to performing any tests, the liquid applied flashing must be allowed to fully cure per the manufacturer’s instructions.

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Testing requirements

Tests used in this standard are based on recognized AAMA, ASTM, or other industry-standard tests, which may have been modified. Test procedures and pass/fail requirements discussed in this article are based on laboratory-controlled conditions. AAMA 714 delineates testing requirements for the following performance characteristics:

• Adhesive strength to substrates. Perform a 180-degree peel adhesion test as specified in Section 8.1 of ASTM C794-18(2022), Standard Test Method for Adhesion-in-Peel of Elastomeric Joint Sealants. The substrates tested must be representative of those used in actual construction, but must include at least the following: concrete masonry units (CMUs), mortar substrate, OSB, and plywood.
• Water penetration resistance around nails or fasteners. Similar to AAMA 711, the flashing is applied to OSB, plywood, or exterior-grade glass-faced gypsum board. Next, two fasteners, a galvanized roofing nail and a zinc-plated #8 pan head wood screw, are driven through a slotted vinyl shim, through the liquid applied flashing and into the substrate. An open-ended watertight cylinder encircles the area and is filled with water, and another container is placed under the assembly being tested. After the test period, if water is found in the bottom container, on the fastener shanks, or on the side or underside of the substrate, the test is reported as a failure. This test is performed both before and after thermal cycling.
• Accelerated aging with UV light exposure. A minimum exposure time to UV light is expected before the liquid-applied flashing is covered by exterior facade materials and, therefore, degradation of liquid-applied flashing materials due to UV exposure should be considered. Testing is performed similar to the procedure described earlier for self-adhering flashing and the light source test chambers must conform to ASTM G154 and ASTM G155. After exposure, perform adhesion tests as specified in ASTM C794.
• Elevated temperature exposure. The liquid-applied flashing must remain stable through the thermal exposure expected during the life of the building. Prepared specimens may be classified for three levels of elevated temperature: level 1, 50 C (122 F), level 2, 65 C (149 F), and level 3, 80 C (176 F). After seven days of exposure at the desired level, perform adhesion tests per ASTM C794.
• Thermal cycling/freeze-thaw. Prepare specimens per ASTM C794. The specimen is then exposed to a high temperature for eight hours, followed by a low temperature for 16 hours. This cycle is repeated 10 times and afterward, the specimen must pass an adhesion test per ASTM C794.
• Crack bridging ability. Building settlement, joint movement between dissimilar materials, and thermal cycles will lead to cracks and misaligned joints. The liquid-applied flashing must have adequate elastomeric properties to maintain the water-resistive seal through these movements. Samples are tested using a modified version of ASTM C1305/C1305M-16, Standard Test Method for crack Bridging Ability of Liquid-Applied Waterproofing Membrane.
• Water immersion. Prepare three liquid-applied flashing specimens per ASTM C794. Perform a peel adhesion test per ASTM C794 over one half the bonded length of a specimen and then the specimen is immersed in water for seven days. After seven days of water immersion, a second peel adhesion test is performed per ASTM C794.
• Damp surfaces. This standard also provides a procedure for testing the adhesive bond strength of the liquid-applied flashing when applied to a damp surface. This includes conditioning for damp surface testing, requirements for adhesion bond strength, and testing for water vapor permeability per ASTM E96/E96M-22ae1, Standard Test Methods for Gravimetric Determination of Water Vapor Transmission Rate of Materials’ Method B.

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Sealants, adhesives, and other building materials that come in to contact with liquid-applied flashing must be chemically compatible. Always check with the product manufacturer(s) to confirm compatibility. This could also be confirmed through testing in accordance with AAMA 713 where necessary.

Installation guidelines

Successful flashing performance depends on adequate adhesion between the flashing and the substrate it is adhered to, as well as the installation conditions. The flashing product must be used in a way that allows it to remain attached to the substrate while maintaining a moisture seal throughout its service life. AAMA 714 includes optional recommendations for field applications. The information in Appendix A should be considered optional and are intended to address field application, not laboratory.

When using a liquid-applied flashing product, the following issues should be considered:

• Where the product is used (i.e. on a wall or a flat surface, such as a sill)
• The presence of dust, dirt, or other contaminants
• Moisture conditions
• Fastener penetrations
• Installation issues, for example blisters
  or non-adhered areas
• Temperature conditions

AAMA 714 Appendix A provides a table which the flashing manufacturer can fill out to indicate the lowest temperature at which the specific liquid-applied flashing product provides an adhesive bond strength of at least 0.9 newtons per mm² (5 lb per linear in.) to the substrates indicated. If a product must be installed at temperatures lower than what is recorded in the table, then an adhesive/primer should be used as an aid.

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When an adequate adhesion is not achieved at any temperature, which is often the case for loosely bonded surfaces such as fiberglass-coated gypsum board, the flashing manufacturer is permitted to indicate “use adhesive primer” in the table, in place of a minimum temperature. If this is provided in the table, users of liquid-applied flashing are advised to take caution as the effectiveness of the flashing depends on the temperature at which it is applied. AAMA 714 Table A1 provides a means to request the lowest temperature to achieve minimum adhesion for the following substrates:

• OSB
• Plywood/wood framing and studs
• PVC (classifications 1-4)/ABS
• Fiberglass-coated gypsum sheathing
• Fiberboard; fibrous sheathing board
• Bare metal surfaces; aluminum/steel/others
• Aluminum with primed/painted surface
• Steel with primed/painted surface
• WRB building paper, asphalt impregnated
  (all weights)
• WRB felt paper (all weights)
• WRB – polyolefin
• WRB – films/coated laminates
• Concrete masonry unit (CMU)
• Poured concrete
• Foam-insulated sheathing
• Exterior gypsum board (not fiberglass coated)
• Laminated fiber sheathing board

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As noted previously, OSB and fiberglass can provide a highly variable or loosely bonded surface, resulting in difficult adhesion conditions without the use of a primer. For liquid-applied flashing, the same applies to fiberboard. As a highly variable substrate, it is difficult to predict the adhesion performance of liquid-applied flashing products to OSB. Although adequate adhesion is often achievable on warm, dry OSB, it is generally advisable to use an adhesive/primer.

Common in the southeast U.S., exterior stucco facade is often directly applied to CMU walls without the use of a drainage cavity (surface barrier wall system). For these applications, it is essential to have a strong bond between the stucco and the CMU wall. When a liquid-applied flashing is used, it should not act as a bond break to the stucco. Consequently, provisions are made either in the formulation of the liquid-applied flashing or with a secondary application of an adhesion promoting substance for the direct applied stucco.

Meeting a growing need

With the increased application of self-adhering and liquid-applied flashing for water protection, these updated standards come at an opportune time.

“Liquid-applied flashing products are realizing increasing application for sealing building interfaces, including flashing around windows and doors,” says Jim Katsaros, chair of the FGIA Flashing Committee.

AAMA 711-22 and AAMA 714-22 are referenced in both the International Residential Code (IRC) and the International Building Code (IBC) as a requirement for using these materials in door and window flashing applications.

Author

Aaron Blom joined the Fenestration and Glazing Industry Alliance (FGIA) in 2021 and is responsible for conducting and developing the association’s professional education programs. He began his career in 2007, as a technical representative for an aluminum framing systems manufacturer, and represented a major fenestration producer, where he focused on the specification and sale of fenestration systems for monumental commercial construction projects. Blom also has worked for a multidivisional specialty subcontractor. He can be reached at ablom@fgiaonline.org.

Source URL: https://www.constructionspecifier.com/specifying-and-installing-flashing-around-exterior-wall-openings/

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