Curtain Wall Embedded Parts: Structural, Operable & Interior Guide

What Curtain Wall Embedded Parts Actually Do

Embedded parts serve as the mechanical interface between two systems that behave very differently: a concrete or steel structural frame that moves slowly under long-term load, and a glass-and-aluminum curtain wall that expands, contracts, and deflects rapidly with temperature and wind. The embedded part must accommodate both while transmitting defined loads cleanly.

The four primary load paths through an embedded part are:

• Dead load transfer: The self-weight of the curtain wall panels — typically 25 to 50 kg/m² for glass and aluminum systems — is carried vertically through the embedded anchor back to the slab edge or column face.
• Wind load transfer: Positive and negative wind pressure on the facade generates in-plane and out-of-plane forces. In high-rise applications, design wind pressures commonly reach 2.0 to 4.0 kPa on building corners and edges.
• Seismic load accommodation: In seismic zones, embedded parts must allow interstory drift — typically ±25 mm to ±50 mm of relative movement between floors — without fracturing the anchor or the curtain wall frame.
• Thermal movement allowance: Aluminum expands at 23 × 10⁻⁶ /°C, roughly twice the rate of concrete. Over a 10-meter panel height across a 60°C temperature swing, that is 13.8 mm of differential movement that embedded connections must accommodate through slotted holes or adjustable bracket systems.

Are Curtain Walls Structural? Understanding the Distinction

A conventional curtain wall is non-structural by definition: it spans between floors, carries its own weight, resists wind pressure, and transfers those loads to the building frame — but it does not carry floor loads, roof loads, or the weight of other building elements. This is the defining characteristic that separates a curtain wall from a load-bearing facade or a structural glazed wall.

However, the line blurs in two scenarios:

• Structural curtain walls in low-rise construction: Single-story commercial buildings sometimes use curtain wall mullions as the primary lateral resisting element along one facade, particularly when the structural bay is entirely glazed. In these cases, the mullions and their embedded part connections are designed to transfer lateral loads into the foundation.
• Point-fixed structural glass systems: Patch-plate and cable-net glazing systems used in atriums and canopies transfer loads through the glass itself to perimeter frames or tension cables. These are technically structural glazing, not curtain walls, but they share the same embedded anchor logic at the support points.

For standard multi-story curtain walls on commercial towers, the embedded parts are designed for facade loads only. The structural engineer specifies the embedded part geometry and position; the curtain wall engineer designs the bracket that connects to it.

Can Curtain Walls Be Operable?

Yes — but the operable portions are panel-level features, not system-level ones. A standard stick-built or unitized curtain wall provides the fixed, weathertight envelope. Within that envelope, individual panels can incorporate:

• Top-hung or side-hung casement vents (typical opening areas: 0.3 to 1.2 m² per vent)
• Tilt-and-turn windows for maintenance access on mid-rise facades
• Bottom-hung hopper vents for natural ventilation strategies in double-skin curtain wall systems
• Motorized louver panels integrated into the outer skin of a double-facade system

The embedded parts are unaffected by whether panels are operable or fixed — the anchor locations are determined by the structural grid, not the panel type. What changes is the mullion sizing: operable panels introduce additional dead load from hardware (hinges, operators, locking mechanisms) that the transom and the curtain wall bracket must carry.

Can Curtain Walls Be Used on Interior Applications?

Interior curtain wall applications are common in large commercial, retail, and institutional buildings. The same stick-built or unitized system used on an exterior facade can be installed on interior boundaries to create:

• Glass-walled conference rooms and executive offices in open-plan floors
• Atrium separation walls between occupied floors and circulation voids
• Lobby feature walls and internal retail storefronts in airports, shopping centres, and transit hubs
• Fire-rated internal glazed screens (fire-rated curtain wall systems achieve up to EI 120 — 120-minute integrity and insulation ratings)

Interior installations typically use lighter embedded parts than exterior applications because wind load is eliminated. The governing loads become dead weight and the impact / accidental loads specified by the building code for interior partitions — usually a horizontal point load of 0.5 to 1.5 kN applied at 1.1 m above floor level. Seismic drift provisions still apply in seismic zones, even for interior walls.

Types of Curtain Wall Embedded Parts and Their Selection Criteria

The correct embedded part type depends on the structural substrate, the load magnitude, and the required adjustability range. The four main categories:

Cast-in channels offer the best combination of load capacity and on-site adjustability for high-rise unitized curtain walls, where bracket positions must be fine-tuned after the concrete frame has been surveyed. Precast inserts are preferred in factory-controlled environments where positional tolerance can be held to ±2 mm, tighter than the ±5 to ±10 mm typical of site-cast concrete.

Structural Engineering Requirements for Embedded Parts

Embedded parts for curtain walls are designed under a combination of facade engineering standards and concrete anchor standards. The key design references in current practice include:

• ACI 318 Appendix D / ACI 318-19 Chapter 17: Governs concrete anchor design in North American practice. Covers concrete breakout, pullout, and side-face blowout failure modes.
• ETAG 001 / EAD 330232: European Technical Approval Guideline for metal anchors. Mandatory for CE-marked anchors used in European projects.
• AAMA 501.6 / AAMA TIR-A11: American Architectural Manufacturers Association test methods for curtain wall anchor connections, including seismic drift simulation.
• EN 1992-4 (Eurocode 2, Part 4): Eurocode design standard for fastenings to concrete, unified across post-installed and cast-in anchor types since 2018.

A correctly designed embedded part includes a minimum edge distance of 6× the anchor diameter from any concrete edge, and minimum spacing of 3× the anchor diameter between adjacent anchors in a group. Violations of these minimums trigger steep reduction factors that can reduce allowable capacity by 40% or more.

Installation Tolerances and Coordination with the Structural Frame

Positional accuracy of curtain wall embedded parts is critical because the curtain wall bracket system has a finite adjustment range — typically ±20 mm in three axes for a standard three-way adjustable anchor bracket. If embedded parts fall outside this envelope, remediation options are expensive: post-drilling, weld-on extension plates, or complete re-anchor in a new location.

Best practice on major projects includes three coordination steps:

• Pre-pour survey: The structural frame is surveyed after formwork is set but before concrete is poured. Embedded part templates are checked against the structural drawings. Any discrepancy greater than 5 mm is corrected before the pour.
• Post-strip survey: After formwork is stripped, the as-built positions of embedded parts are recorded with total station or 3D laser scanning. This data is fed to the curtain wall fabricator to adjust bracket offsets before fabrication.
• Frame acceptance criteria: Most curtain wall contracts specify that the structural frame must be within ±10 mm of theoretical position in plan and elevation, and within ±5 mm plumb over any 3-meter height, before the curtain wall contractor takes possession of the floor for installation.

Material and Corrosion Considerations

Embedded parts operate at the boundary between two corrosion environments: the alkaline concrete interior (pH 12–13) and the exposed bracket zone subject to moisture, pollution, and — in coastal locations — chloride deposition. Material selection must address both zones.

• Hot-dip galvanized carbon steel (HDG): Standard specification for interior and moderate-exposure facades. Zinc coating thickness of 85 microns minimum (per ISO 1461) provides 40–60 years of service life in a C3 corrosivity category environment.
• Stainless steel (Grade 316L): Required for coastal, industrial, and swimming pool enclosure applications. The molybdenum content of 316L provides critical resistance to chloride pitting that standard 304 grade cannot match. Expected service life exceeds 50 years in C5-M (marine) environments.
• Duplex stainless steel (2205): Used when both corrosion resistance and high strength are needed. Yield strength of 450 MPa versus 220 MPa for 316L, allowing more slender embedded plate geometry where concrete cover is limited.

Bi-metallic corrosion (galvanic action) is a persistent risk where aluminum brackets contact steel embedded parts. A neoprene or EPDM isolation washer, minimum 3 mm thick, at every bracket-to-embedded-part contact surface is a code requirement in most facade specifications and should never be omitted to save cost.