Choosing Sealants for Structural Glazing Applications

In modern architecture, glass isn’t just a window—it’s a structural element. From soaring curtain walls to point-supported facades, glass is being used to create the visual language of transparency and openness. But that vision only holds together if the sealants behind the scenes do their job. Structural glazing relies on high-performance sealants that bond, flex, and endure under extreme environmental and mechanical stress—often without any mechanical fasteners.

For building materials distributors, supplying the right structural glazing sealants isn’t just about stocking a few SKUs. It’s about understanding project requirements, certification needs, and how to support contractors and glaziers in applications where failure simply isn’t an option.

What Is Structural Glazing?

Structural glazing is the technique of bonding glass to metal frames using specialized sealants—most commonly silicone—eliminating the need for visible mullions or brackets. It creates uninterrupted glass surfaces on facades, skylights, atriums, and canopies.

These systems are engineered to handle:

Wind load and building sway

Thermal expansion and contraction

UV exposure and long-term weathering

Dynamic joint movement over years of service

Types of Structural Glazing Systems

Four-Sided Structural Glazing (SSG)

All sides of the glass panel are bonded with sealant to the frame—no mechanical retention.

Two-Sided SSG

Vertical sides are bonded; top and bottom are mechanically retained.

Toggle or Captured Systems

Sealant works in tandem with pressure plates or toggles—common in seismic zones.

Each system must be engineered with a tested and certified sealant, backed by rigorous quality control and field support.

Sealant Selection Criteria

Structural Strength (ASTM C1135, ETAG 002)

Must withstand live loads, dead loads, and dynamic wind pressures without creep or bond failure. Manufacturers typically provide allowable design stress values.

UV and Weather Resistance

Only silicone sealants are stable enough under full UV exposure for structural glazing. Polyurethane and hybrid chemistries are not acceptable.

Movement Accommodation

Typical systems require ±25% movement capability to absorb expansion, sway, and settlement.

Adhesion to Substrates

Sealants must be tested and approved for the specific glass, spacer, and frame finish used. Surface compatibility is critical.

Cure Time and Depth

Structural silicones often require deep cure (10+ mm), and must reach full strength before load is applied. Distributors should provide guidance on cure windows based on temperature and humidity.

Product Categories for Distribution

Two-Part Structural Silicones

Rapid curing

Mixed with static or dynamic mixers

Requires dual-cartridge or pump application

One-Part Structural Silicones

Slower cure (via atmospheric moisture)

Easier for small-scale or patch repairs

Used for SSG and weatherseal interface

Primer Systems

Ensure bond strength on anodized aluminum, ceramic frit glass, or coated substrates

Cleaners and Surface Prep Agents

Required to meet warranty conditions and ensure consistent bond

Distributor Responsibilities and Differentiators

Stock products with ETA/ICC/ASTM approvals

Structural glazing is a life-safety application. Products must be backed by engineering data and third-party testing.

Support mock-up and lab testing

Many projects require adhesion testing or system compatibility testing before approval. Partnering with the sealant manufacturer to support this process builds credibility.

Bundle tools and logistics

Include mixing tips, backup rods, tapes, and application guns in your offering. Structural glazing sealants can’t be applied with standard caulking tools.

ERP and Inventory Considerations

Shelf-life tracking: Many structural sealants have a 9–12 month shelf life. Use ERP to flag aging inventory and rotate stock.

Batch traceability: Projects often require documented batch numbers for warranty and QA records.

Project tagging: Associate sealant SKUs with project files for reorders, warranty claims, or inspection audits.

Common Pitfalls to Help Customers Avoid

Using weatherseal-grade silicone for structural joints

Applying over contaminated or improperly prepped substrates

Rushing load-bearing before full cure

Failing to validate system compatibility between spacer, glass, and frame coatings

Why It Matters

Failure in structural glazing isn’t cosmetic—it’s catastrophic. By supplying certified products, accurate data, and project-ready support, distributors don’t just move product. They uphold the safety and success of high-profile builds. In a field where liability is measured in glass panels, confidence in your sealant supply chain is the clearest line you can draw.