Air-Shield Transitional Membranes

This document has been created as an addendum to our Air-Shield technical data sheets to provide some additional information regarding the application of transition membranes for rough openings, such as windows and doors.

To remain current in the industry and provide our customers with an economical and user-friendly air barrier assembly, we would like to provide three different application procedures to address the use of transition membranes. The first is the use of our Air-Shield self-adhesive membrane as we have always used, the second is the use of our Air-Shield LMP vapor permeable fluid-applied membrane, and the third is our Air-Shield HT high-temperature self-adhering transition membrane. Each of these systems is suitable for various substrates, including concrete, concrete masonry, OSB, plywood, exterior sheathing, and metal surfaces. Following are the procedures that we would recommend to achieve continuity of the transition membrane.

Air-Shield – Self-Adhesive Transition Membrane (to be used with air/vapor barrier materials)

• Condition the area to be detailed using Mel-Prime or Mel-Prime W/B. On exterior sheathing surfaces, ensure that enough primer has been applied, as typically two coats of primer are required.
• Pre-cut the Air-Shield for each area of the rough opening to ensure ease of handling.
• Apply the first pre-cut strip at the base of the rough opening by removing the release paper and rolling firmly into place, ensuring that there is a minimum of 3” of membrane extending onto the wall. Also, ensure that there is a minimum of 3” of membrane extending into the rough opening.
• Repeat this procedure for the vertical areas of the rough opening, and finally apply the membrane at the header portion of the opening.
• Ensure all edge overlaps are a minimum of 2” and end-to-end overlaps are 4”.
• Seal all terminations with Pointing Mastic.
• Apply the specified air barrier membrane system on the whole wall ensuring adequate overlap with the transition membrane.

Air-Shield LMP – Fluid Applied Transition Membrane (to be used with vapor permeable materials)

• If applying this system on exterior sheathing, OSB, or plywood, ensure that any joints or gaps ¼” or greater are initially filled with Air-Shield Joint Filler prior to application of the membrane system.
• Apply a minimum 30 wet mil coat of fluid Air-Shield LMP ensuring that there is a minimum of 3” of membrane extending onto the wall and 3” into the rough opening.
• Embed a layer of glass mesh into this first coat.
• While the first coat of Air-Shield LMP is still wet, completely cover the glass mesh with a second coat of Air-Shield LMP at 30 wet mils thick, again extending 3” onto the wall and 3” into the rough opening. This will allow for maximum adhesion of the two coats.
• If the substrate is concrete or concrete masonry, the glass mesh is not required. Apply Air-Shield LMP in one or two coats in order to achieve a 60 wet mil thick coat.
• Apply the specified air barrier membrane system on the whole wall ensuring adequate overlap with the transition membrane. It is important to review each application, as there may be situations that require modification of these procedures based on project requirements.

In addition to these two options, W. R. Meadows now offers Air-Shield HT, a high-temperature self-adhering transition membrane designed for use in elevated service conditions.

Air-Shield HT – High-Temperature Self-Adhering Transition Membrane

• Condition the area to be detailed using Mel-Prime, Mel-Prime N.E., or Mel-Prime W/B. Surfaces must be clean, dry, and smooth, free of projections that could puncture the membrane.
• Pre-cut the Air-Shield HT for each area of the rough opening to ensure ease of handling.
• Apply the first strip by removing the release paper and pressing firmly into place, recessing at least 1/2″ (13 mm) from the masonry face. Ensure there is a minimum of 3″ of membrane extending onto the wall and 3″ into the rough opening.
• Repeat this procedure for the vertical jambs and finally across the head of the opening. Minimum overlaps should be 2.5″ (63.5 mm). Seal seams and terminations with Pointing Mastic or BEM from W. R. Meadows.
• If not embedded in the masonry joint, mechanically fasten the top edge using Termination Bar and seal with Pointing Mastic or BEM.
• Where the cavity is open, provide continuous support below the flashing width to prevent sagging and water collection. For OSB substrates, perform adhesion tests prior to full installation to confirm compatibility.
• After detailing with Air-Shield HT, apply the specified air barrier membrane to the full wall ensuring proper overlap with the transition membrane.

When to use: Select Air-Shield HT where elevated service temperatures (up to 240°F / 117°C) are expected — such as behind dark claddings, under metal panels, at spandrel beams, or in roofing tie-ins — and where a durable, high-temperature thru-wall flashing is needed.

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