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Importance of Sealer for EIFS Projects

High-performing, drainable EIFS provides the building industry with a complete wall cladding system and a simple-to-use solution toward compliance with the current energy code. Drainable EIFS wall systems, like StoTherm® ci Wall Systems, include five control layers (vapor, air, water, thermal, and water shedding) that work together to create a tight building envelope to ensure an energy-efficient, durable, safe, sustainable, and attractive building. 

A tight building envelope relies on keeping it air and weather-tight. The use of a quality sealant should be used as perimeter weather seal around windows, doors, and other through wall penetrations, thermal expansion and contraction joints, and control joints to prevent air and moisture infiltration. Sto’s sealant, StoSeal STPE Sealant provides a high-movement, low-odor, non-sag sealant for use in new construction or renovation projects from a single manufacturer.

Why Are Sealants Needed?

EIFS systems, like all wall claddings, require sealants around doors, windows, service openings, and between dissimilar materials to help ensure a water-resistant and airtight building envelope. Sealants also absorb thermal expansion and contraction.

Sealant Issues with EIFS Cladding

Inadequate application or missing sealants to EIFS or any claddings will provide a path for unwanted air and moisture into EIFS cladding that can lead to premature deterioration and failure of the EIFS finish coat, which typically is not covered by manufacturers’ warranties.

Failures commonly occur when the sealant is applied to the finish coat instead of the mesh-reinforced base coat, the sealant is not regularly inspected after reaching its life expectancy, commonly five to ten years, if the sealant was applied over a dirty substrate, the wrong modulus was used, and more.

Properly Sealing EIFS Projects

The airtightness of the EIFS system’s joints depends on the sealant’s adhesion, durability, and compatibility with the EIFS. Therefore, when constructing an EIFS system, it is vital to use a high-quality sealant, like StoSeal STPE™ Sealant. In addition, applicators must follow the manufacturer’s application instructions to achieve the EIFS project’s performance requirements and avoid sealant failure. 

Why Use STPE Sealants for EIFS Projects

High-performing EIFS sealants offer flexibility, durability, sustainability, and ease of application. The building industry utilizes several sealants, including polyurethane, silicone, and Silyl Terminated Polyether (STPE).

Polyurethane and silicone lack characteristics that impact their effectiveness and durability: 

  • Polyurethane sealants lack adequate weather resistance.
  • Silicone’s bonding properties may fail under strong shear forces.
  • Non-sustainable, non-recyclable polyurethane and silicone break into unhealthy chemicals if heated past their maximum operating temperatures. 

Fortunately, sustainable and fast-curing STPE sealants combine silicone’s weather resistance and polyurethane’s strength to produce a long-lasting sealant with superior adhesion, strength, and flexibility. Fast-curing STPE sealants also maintain their color by minimizing exposure to debris and dust, which can cling to the sealant.

Silyl Terminated Polyether (STPE) Sealants for EIFS Projects

A tight building envelope keeps outside elements (e.g. air and moisture) from infiltrating a structure. Correctly applying a high-performing STPE joint sealant is a vital step towards weatherproofing an EIFS building’s exterior and protecting its health and integrity. 

Silyl Terminated Polyether (STPE) sealant technology provides several superior high-performance features that will contribute to a long-lasting, energy-efficient EIFS system:

Durable and long-lasting STPE sealants for EIFS

  • Durable and Weather Resistant: STPE sealants perform well in most weather conditions and at low temperatures (unlike polyurethane sealants) with little adhesion failures, cracking, splitting, or discoloration.
  • Flexibility: STPE sealants’ elongation characteristics can endure structural movement and withstand substrate vibrations or oscillations more effectively than silicone sealants.
  • UV Resistant: STPE sealants will not crack or yellow after extended periods of UV-light exposure, unlike polyurethane sealants.
  • Non-Reactive: STPE sealants will not corrode or oxidize metals.
  • Storage Stability: STPE sealants have an excellent shelf life when not exposed to moisture.
  • Cold Resistant: STPE sealants retain their properties to -50°F (-45°C).
  • Adhesion: STPE sealants have excellent cohesive strength that adheres more effectively to many substrates, like metals, concrete, wood, plastics, and ceramics, compared to polyurethane and silicone sealants.

STPE sealants for EIFS Ease of Application

STPE sealants may not require priming on most substrates and can create a continuous smooth surface. In addition, you can paint STPE sealants after 24 hours. 


Recyclable STPE products contain extremely low or no VOCs, unlike other sealants prone to off-gassing, like polyurethane and silicone, which will break into unhealthy chemicals if heated past their maximum operating temperatures. 

StoSeal STPE™ High-Quality, Versatile Adhesive Sealant

StoSeal STPE™ Sealant from Sto® Corp. is a high-performing, low-odor, isocyanate-free, one-part hybrid sealant with a VOC content of 8 grams per liter. It is a durable, flexible, low-modulus, non-sag sealant with excellent moisture and weathering resistance.

StoSeal STPE™ Sealant bonds to most building materials (masonry, concrete, wood, stone, fiber cement, vinyl, stucco) and can seal gaps and joints around floor lines, wall penetrations, fixtures, etc., for a tight building envelope.

The superior adhesive properties of StoSeal STPE™ Sealant work effectively with 

StoVentec®, StoTherm® ci, StoPowerwall®, and StoQuik® exterior wall systems 

and with StoGuard® Air and Water-Resistive Barrier systems for vertical above-grade building restoration applications and new opaque walls.

The Best Sealant for EIFS – StoSeal STPE Sealant

Applying StoSeal STPE™ Sealant for EIFS projects, according to the manufacturer’s instructions, will contribute significantly to creating a tight building envelope.

When correctly applied, StoSeal STPE™Sealant produces a durable, long-lasting, sustainable sealant that contributes significantly to a tight building envelope.

For more on the importance of sellers for EIFS projects and the benefits of StoSeal STPE™, contact our professionals at (800) 221-2397!

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