Technical Guide

Curtain Wall Details: What to Look For in Drawing Review

A guide to reviewing curtain wall systems on construction documents

Last updated: February 2026•Technical Guide

Curtain walls are non-structural exterior cladding systems that hang from the building structure like a "curtain." They resist wind loads and transfer their self-weight to the structure at each floor through anchors, but they do not carry any building loads. As one of the most complex and expensive building envelope systems, curtain wall detailing requires careful coordination across multiple disciplines. Understanding how to review these details is a key part of construction drawing review.

Stick vs. Unitized Systems

Stick-Built System

Mullions and glass are assembled piece-by-piece on site. Vertical and horizontal mullions are attached to the structure, then glass and panels are installed into the frame.

Best for: Low-rise buildings (1-6 stories), complex geometries, small projects

  • Lower upfront cost
  • More flexible for irregular layouts
  • Field-assembled joints — quality depends on installer skill
  • Slower installation — weather-dependent
  • More field sealant joints

Unitized System

Pre-assembled panels (typically one floor high, one module wide) are fabricated in a controlled factory environment and installed as complete units on site.

Best for: High-rise buildings (6+ stories), repetitive facades, fast-track schedules

  • Factory quality control — better waterproofing
  • Fast installation — crane-set one unit at a time
  • Built-in movement accommodation at interlocking joints
  • Higher fabrication cost, longer lead time
  • Requires early design freeze — changes are expensive

Key Detail Locations to Review

A complete curtain wall drawing package should include details at each of these critical locations. Missing details are a red flag — they often indicate unresolved coordination issues. Refer to the architectural detail types guide for more on how details are organized in a drawing set.

Head (Top of Vision Glass)
Anchor connection to structure above
Thermal break continuity
Head receptor channel and gaskets
Perimeter sealant and backer rod
Spandrel panel attachment above
Firesafing at slab edge
Sill (Bottom of Vision Glass)
Sill flashing and weep system
Setting blocks for glass support
Interior finish transition
Condensation gutter or weep slots
Pressure equalization chamber
Integration with interior sill/millwork
Jamb (Sides of Glass)
Mullion gasket and glazing pocket depth
Structural silicone vs. captured glazing
Thermal break alignment
Adjacent wall transition and sealant joint
Perimeter fire safing at columns
Blind mullion at corners
Stack Joint (Floor Line)
Vertical movement accommodation (live load deflection)
Split mullion with sliding gasket or cover
Firesafing and smoke seal at slab edge
Structural anchor at each floor
Thermal break continuity across joint
Interior head/sill finish at each floor
Corner Condition
Corner mullion structural capacity
Glass-to-glass butt joint vs. corner post
Thermal performance at corner (thermal bridging risk)
Sealant compatibility at glass-to-glass joint
Corner anchor and structural backup
Interior corner finish trim
Parapet/Roof Termination
Top-of-wall cap flashing and counterflashing
Air barrier and vapor retarder termination
Metal coping attachment and expansion joints
Transition from curtain wall to roofing membrane
Lightning protection bonding
Maintenance access provisions

Thermal Performance Considerations

Thermal Break
Modern curtain wall systems include a polyamide (nylon) or polyurethane thermal break that separates the interior and exterior aluminum surfaces. Without this, the highly conductive aluminum frame becomes a major thermal bridge, causing condensation and energy loss.
U-Value Requirements
Energy codes (ASHRAE 90.1, IECC) set maximum U-values for the overall fenestration assembly. Typical requirement: 0.36-0.42 BTU/hr·ft²·°F for commercial buildings in Climate Zones 4-6.
Condensation Resistance
CRF (Condensation Resistance Factor) must be specified for cold climates. Target CRF of 60+ for most commercial applications. AAMA 1503 testing standard.
Spandrel Insulation
Non-vision areas (spandrel panels) require back-pan insulation to meet code U-values. Verify insulation R-value and vapor barrier location relative to dewpoint.

Multi-Discipline Coordination Issues

Curtain wall installation touches nearly every trade. Identifying MEP-structural clashes early is critical, and proper firestopping at slab edges is one of the most commonly missed items.

Structural
Slab edge embeds must be cast before curtain wall installation. Verify embed locations, edge-of-slab tolerance (±1"), and deflection criteria (L/360 typical, L/240 for some systems).
Mechanical
Perimeter heating/cooling units (fan coils, radiant panels) must clear mullion anchors and firesafing. Verify clearance between slab edge and interior face of curtain wall.
Fire Protection
Perimeter firesafing (safing insulation + smoke seal) is required at every floor slab. Sprinkler heads near curtain wall must maintain required clearance from spandrel glass.
Electrical
Automated shade pockets, motorized vents, and facade lighting require power and control wiring routed to the curtain wall. Verify conduit locations in slab edge.
Interior Design
Interior sill heights, column covers, and ceiling-to-mullion transitions must be coordinated. Drywall returns to mullions need backing and thermal considerations.
Waterproofing
Below-grade curtain wall transitions to waterproofing membrane. The air/water barrier must be continuous from below-grade wall through curtain wall perimeter sealant.

Related Resources

Waterproofing Details Guide
Building envelope moisture protection systems.
Firestopping Guide
Perimeter firesafing at curtain wall slab edges.
Window Types Guide
Fenestration types and glazing options for buildings.
Waterproofing Failures in Construction
Common envelope failures and how to prevent them.
Envelope Analysis Feature
Automated building envelope review with AI.
Articulate for Architects
How architects use Articulate for drawing review.

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Sources

AAMA CW-DG-1 — Aluminum Curtain Wall Design Guide Manual

ASTM E330 — Standard Test Method for Structural Performance (Uniform Static Air Pressure)

ASTM E331 — Standard Test Method for Water Penetration

ASHRAE 90.1 — Energy Standard for Buildings Except Low-Rise Residential