Enhance Building Envelope Performance With STPE Liquid Flashings and Air Barriers | Bostik US

Learn how STPE technology enhances liquid flashings and air barriers with strong adhesion, flexibility and vapor permeability for building envelopes.

As a construction materials brand owner, you know the materials you use can directly influence the building envelope’s ability to improve overall energy efficiency as well as your customers’ ability to properly install the product.

As flashings and air barriers become increasingly critical components in construction, choosing the right technology is crucial to maximizing the application and performance benefits – that's why it may be beneficial to consider the value of liquid flashings and air barriers, as they can provide unique benefits you may not get with other flashing and air barrier technologies.

Learn about key requirements for liquid flashings and air barriers and why silyl-terminated polyether (STPE) technology, also known as silyl modified polymer (SMP) technology, can help achieve key goals.

The Value of Liquid Flashings and Air Barriers

Liquid flashings and air barriers are products designed to integrate seamlessly into the building envelope. They work together as part of a continuous building envelope system.

Liquid flashings protect detail areas such as windows, doors, penetrations and seams.
Liquid air barriers provide protection across larger wall surfaces to help ensure building envelope continuity.

Together, they help provide:

Air leakage protection: By controlling airflow, heat transfer and radiation through the building envelope, liquid flashings and air barriers can reduce air leakage and help decrease energy usage, which can result in reduced costs for building owners.
Vapor permeability: Liquid flashings and air barriers can be designed to be vapor permeable, allowing wet substrates to dry out throughout the life of the building. This reduces jobsite delays due to weather and helps prevent the accumulation of moisture in the wall cavity.

While both help prevent unwanted air and moisture intrusion, each application requires your bonding and sealing solution to offer varied capabilities so that it can perform effectively.

Liquid Flashing Bonding and Sealing Requirements

Liquid flashings play a key role in protecting rough openings, seams and transitions in areas that are vulnerable to moisture intrusion. Because liquid flashings are designed for detail areas, they must conform to uneven surfaces, corners, tight spaces and bridge gaps. Their fluid application allows them to cling tightly to every conformation of the substrate and cure into a seamless elastomeric layer that maintains uniform protection across irregular surfaces.

To achieve this, liquid flashings need a bonding and sealing solution that dispenses and tools easily and adheres strongly to a variety of building materials, helping to ensure the liquid flashing can contact and wrap into complex openings or surfaces without pulling away or creating voids.

Further, the ability to adhere to damp substrates or tolerate application in wet weather can provide consistent performance results to those detail areas even under challenging weather-related jobsite conditions. To successfully achieve this, it is also critical for the bonding and sealing solution to be paired with a vapor permeable solution. Breathability of a liquid flashing allows damp substrates to dry out and water vapor in the wall cavity to escape, preventing mold, substrate degradation as well as further intrusion of liquid moisture.

Once cured, liquid flashings also must be flexible so they can shift with structural movement and still provide proper long‑term protection. Unlike rigid materials, they are designed to move with the building and help maintain energy efficiency. A bonding and sealing solution that offers durable flexibility and maintains adhesion under expansion and contraction means that the flashing will stretch, compress and recover, reducing the likelihood of cracking or losing its seal.

Liquid Air Barrier Bonding and Sealing Requirements

Liquid air barriers are designed to provide continuous protection across large wall areas, supporting overall building performance. They become a fully adhered membrane that bridges surface irregularities, cures without seams and maintains consistent coverage.

Just like liquid flashings, liquid air barriers can be designed to adhere to damp surfaces and be vapor permeable. This design allows incidental moisture within the wall assembly to escape while still preventing air from moving through the structure; otherwise, trapped moisture can lead to rot, mold or reduced thermal performance.

At the same time, liquid-applied air barriers are often exposed to weather during construction before exterior claddings are installed. UV exposure, temperature changes, rain and jobsite conditions can degrade uncured or recently cured membranes, and your liquid air barrier must be designed to withstand all these potential setbacks. This is why air barriers require a bonding and sealing technology that directly supports these application needs, including:

Long‑term adhesion to a variety of building materials, which helps ensure the air barrier maintains a durable, continuous membrane on substrates that expand, contract or shift over time, such as concrete, gypsum and wood sheathing, metal and masonry.
Crack resistance that can allow the membrane to bridge minor substrate cracking or movement without tearing or losing bond.

By pairing long-term adhesion with crack resistance, the bonding and sealing solution helps maintain a tight, uninterrupted layer, even when surfaces move or settle, helping to prevent air infiltration.

Further:

Breathability helps ensure that water vapor can exit the wall cavity, supporting a healthy, long-lasting assembly.
Anti‑weathering capabilities help the membrane withstand UV, temperature and other jobsite conditions without degrading or losing adhesion.

Coupling breathability with anti‑weathering capabilities helps the membrane remain stable and durable throughout exposure, so it continues to bond, seal and perform until the full wall system is complete and throughout the building lifespan.

How Silyl Modified Polymer (SMP) Addresses Liquid Flashing and Air Barrier Bonding and Sealing Requirements

Silyl modified polymer (SMP) technology, also known as silyl-terminated polyether (STPE), is a hybrid, moisture-curing solution that is a strong technological base for both liquid flashing and air barrier applications. By providing one consistent solution across building envelope materials, SMP technology enhances performance for both liquid flashings and air barriers with these capabilities:

Vapor permeable: SMP products can be designed with a high vapor permeability, allowing moisture vapor to pass through while still blocking liquid water, supporting healthy indoor air quality and reducing mold potential.
Immediate waterproofing: SMP products provide instant water resistance upon application, helping protect the structure from rain events during and after curing.
Adhesion to damp substrates: Permeable SMP liquid flashings and air barriers can be applied to damp surfaces, reducing weather delays on jobsites.
Weatherability and UV resistance: The innate durability of the SMP polymer combined with UV stabilizers and antioxidants allows the product to withstand extended outdoor exposure without loss of performance.
Long-term flexibility: SMP liquid flashings and air barriers cure into continuous, elastomeric membranes that can bridge gaps and flex as the building shifts to prevent cracking and help ensure continuous protection of the building.
Versatile adhesion: SMP products bonds securely to a variety of construction materials such as plywood, OSB, gypsum, etc. without the need for primer and self seals around fasteners for airtight continuity.
Comprised of 100% solids: SMP products do not contain any solvents or water, so there is no shrinkage during curing, helping to ensure the product stays exactly where it is initially applied.
Paintability: SMP products are compatible with a variety of paints and coatings to meet aesthetic and finishing requirements.

Ultimately, using the same SMP technology for both liquid flashings and air barriers improves overall building envelope performance by helping to ensure consistent adhesion, uniform flexibility and seamless membrane continuity. This reduces the likelihood of weak points at transitions and helps maintain airtight, watertight protection across the entire building envelope.

How Bostik Can Help with SMP Liquid Flashings And Air Barriers

As the adhesives solutions segment of Arkema, Bostik provides a range of adhesive and sealant technologies that can help you complete your building envelope portfolio and offer your customers high end-use performance as well as improved efficiencies and sustainability in residential commercial construction applications.

Our team understands you need to provide durable, seamless products for window, door and wall applications. In particular, our expertise and formulation testing for SMP technology, also known as silyl-terminated polyether (STPE) technology, helps ensure liquid flashings and air barriers can provide strong, consistent protection while meeting industry standards.

Our featured SMP solutions include:

Liquid Flashings: VSR™ 200A

Bostik’s VSR™ 200A is a one-component SMP intended for use as a liquid-applied flashing. It is free of solvents and isocyanates, helping to enhance worker safety during installation and indoor air quality when the finished building is in use. VSR 200A can also serve as a dual-purpose product for liquid flashings and an installation sealant, because its formulation passes ASTM C920 in addition to AAMA 714. This allows it to seal joints while also acting as a flashing material, which can decrease the number of products needed, simplify inventory and lower installation costs. Further, the easy, trowelable nature of this product allows for fast installation around rough openings, transitions and detailed areas.

Liquid Air Barriers: VSR™ 100A

Bostik’s VSR™ 100A is a breathable, one-component SMP intended for use as a sprayable or rollable liquid applied air barrier product. It is free of solvents and isocyanates; it bonds to most common building materials without priming and allows damp surfaces to dry. This provides value by saving time and labor costs by minimizing delays due to substrate conditions and offering reliable adhesion even in challenging environments. Further, not only can VSR 100A be used as a liquid air barrier, but it can also be a liquid flashing solution since it meets the required standards for each application.

In addition to our SMP products, when you work with Bostik, you’ll also receive:

Technical Support: We are here to help educate your team about our private label solutions, providing assistance as questions arise during onboarding and throughout your use of our product.
Innovative Solutions: Our large portfolio of products across many technologies helps you bridge market gaps between you and installers.
Product Usage Training: Our team will help you understand how to properly apply these solutions for high-performing results.

Ready to learn how SMP can provide consistent protection and long-term durability for both liquid flashings and air barriers? Contact a Bostik expert to find out how we can help streamline installation with a technology that helps you deliver enhanced performance, processing and sustainability.

All information contained herein is believed to be accurate as of the date of publication, is provided “as-is” and is subject to change without notice. To review our full U.S. Legal Disclaimer, visit: https://www.bostik.com/us/en_US/legal-disclaimer/