Aluminium Curtain Wall Systems for Commercial Buildings: Complete Guide SA

🏢 The complete guide to glass facade systems – design, costs, installation, and specifications

Let me take you inside a modern commercial building in Johannesburg or Cape Town. Look at the exterior. Chances are, you’re seeing an aluminium curtain wall system – a floor-to-ceiling glass facade with minimal visible framing. It’s the hallmark of contemporary architecture, and for good reason. These systems flood interiors with natural light, create stunning visual impact, and define the building envelope.

But here’s what most people don’t understand. Curtain walls are not just oversized windows. They’re sophisticated structural systems that bear their own weight, transfer wind loads to the building structure, and must accommodate thermal movement, water penetration, and seismic forces. Getting them right requires specialist knowledge.

In this complete guide to aluminium curtain wall systems, I’ll explain what are aluminium curtain wall systems, compare different types (stick vs unitised), cover design considerations, glass options, thermal performance, installation processes, and cost factors. You’ll learn about commercial glazing standards, structural requirements, and how to specify a curtain wall that performs for decades.

For more commercial guidance, read our shopfront guide, commercial doors guide, or office windows guide. Ready to understand curtain walls? Let’s dive in.

🏗️ What Is a Curtain Wall System?

To answer what are aluminium curtain wall systems, start with the basics.

Definition: A curtain wall is a non-structural outer covering of a building. Unlike traditional windows that sit within structural openings, curtain walls hang (or “curtain”) from the building structure. They bear their own weight and transfer wind loads to the building, but do not support floor or roof loads.

Key characteristics:

• Floor-to-ceiling glass facades with minimal visible framing
• Aluminium framing system that accommodates glass, spandrel panels, and other infills
• Designed to resist air and water infiltration
• Accommodates thermal expansion and contraction
• Handles wind loads, seismic movements, and other building movements

Where are curtain walls used?

• Commercial office buildings
• Corporate headquarters
• Retail flagship stores
• Airports and transport terminals
• Hotels and hospitality buildings
• Educational and healthcare facilities

According to SANS 10400 curtain wall standards and SABS structural glazing standards, curtain walls must meet strict performance requirements for safety and weather resistance.

📦 Stick vs Unitised Curtain Walls

There are two main types of aluminium curtain wall systems. Here’s how they compare.

Stick systems (most common in SA):

Frames are delivered as components (sticks) and assembled on-site. Glass is installed after the frame is complete. Requires scaffolding and is weather-dependent. More affordable and suitable for most South African commercial projects up to 10 storeys.

Unitised systems (premium):

Complete wall panels (frame + glass) are assembled in a factory and delivered to site. Installed by crane, with panels interlocking. Faster installation, better quality control, and less weather-dependent. Higher cost but preferred for high-rise buildings and tight schedules.

Read our custom fabrication guide for more on manufacturing processes.

📐 Design Considerations for Curtain Walls

Successful curtain wall installation starts with proper design.

Structural engineering:

• Wind load calculations for your specific location and building height
• Dead load (self-weight) transfer to building structure
• Movement accommodation (thermal expansion, building sway, seismic)
• Connection details between curtain wall and building frame

Thermal performance:

• U-value (heat loss) – critical for energy efficiency
• Thermal break profiles (essential for aluminium curtain walls)
• Condensation risk analysis – prevent moisture damage

Water and air penetration:

• Pressure-equalised design (rain screen principle)
• Weep holes and drainage paths
• Multiple gaskets and seals
• Testing to ASTM or SANS standards

Fire safety:

• Fire-stopping between floors (prevents fire spreading up the facade)
• Fire-rated glass where required (stairwells, egress paths)
• Compliance with SANS 10400 fire regulations

Read our building construction guide for more on structural integration.

🪟 Glass Options for Curtain Walls

Glass is the dominant material in any curtain wall. Here are the options for commercial glazing.

Spandrel glass (opaque areas): Used to conceal structural elements (slab edges, columns). Heat-strengthened glass with ceramic frit or opaque coating on the back. Cost: similar to vision glass.

Read our double glazing guide for more on insulated glass units.

⚡ Thermal Performance & Energy Efficiency

Curtain walls have a huge impact on a building’s energy performance.

Why thermal performance matters: A poor-performing curtain wall can account for 30-50% of a building’s heating and cooling load. In commercial buildings, this translates to significant operating costs over decades.

Key factors affecting thermal performance:

• Thermal break in framing: Essential for aluminium curtain walls. Polyamide strip separates interior and exterior aluminium, reducing heat flow.
• Glass specification: Double glazing with Low-E coating and argon gas provides best performance for most applications.
• Gaskets and seals: Continuous, high-compression seals prevent air leakage.
• Installation quality: Gaps between curtain wall and building structure must be properly sealed.

Target U-values for curtain walls in South Africa:

• Basic commercial standard: U ≤ 2.5 W/m²K
• Energy-efficient (SANS 10400-XA compliant): U ≤ 2.0 W/m²K
• Premium (Green Star rated): U ≤ 1.5 W/m²K

Read our thermal break guide for more on frame insulation.

🏗️ Structural Requirements & Wind Load

Curtain walls must withstand significant forces. Here’s what engineers consider.

Wind load requirements by building height and location:

• Ground to 10m: Standard wind load (1.0-1.5 kPa)
• 10m to 30m: Increased wind load (1.5-2.5 kPa)
• 30m to 60m: High wind load (2.5-3.5 kPa)
• 60m+ (high-rise): Extreme wind load (3.5-5.0+ kPa)
• Coastal areas: Additional 0.5-1.0 kPa for exposure

Structural testing requirements:

• Air infiltration test (ASTM E283)
• Water penetration test (ASTM E331)
• Structural performance test (ASTM E330)
• Seismic movement test (where applicable)

Connection to building structure: Curtain walls attach to the building’s structural frame at each floor level. Connections must allow for movement (thermal expansion, building sway) while securely transferring wind loads. This is specialist engineering – not a standard window installation.

Read our high wind guide for more on wind load requirements.

🛠️ Stick System Installation Process

Here’s how a typical stick system curtain wall installation proceeds.

Step 1: Site preparation and scaffolding

Full scaffolding is erected around the building perimeter. Safety netting and weather protection may be required.

Step 2: Anchor installation

Anchors (brackets) are fixed to the building structure at each floor level. Precision alignment is critical – errors compound as the wall rises.

Step 3: Mullion installation (vertical members)

Vertical mullions are installed first, attached to the anchors. They must be perfectly plumb and aligned.

Step 4: Transom installation (horizontal members)

Horizontal transoms are installed between mullions, creating the grid that holds glass.

Step 5: Gasket and seal installation

Gaskets are fitted into the frame grooves – these will seal against the glass.

Step 6: Glass panel installation

Glass panels are lifted into place and secured with pressure plates. Glass is heavy – requires mechanical lifting aids and multiple installers.

Step 7: Sealing and finishing

Silicone sealant is applied to all joints. Cover caps snap over pressure plates for a finished look.

Step 8: Testing and quality assurance

Water spray testing, air leakage testing, and visual inspection.

Timeline: Stick system installation typically takes 1-2 weeks per floor, depending on complexity.

🏗️ Unitised System Installation Process

Unitised systems offer faster installation but require crane access.

Step 1: Factory assembly

Wall panels (frame + glass) are assembled in a controlled factory environment. Quality control is consistently high.

Step 2: Delivery and staging

Panels are delivered to site on trucks, often in sequence of installation. Staged on the ground or on designated floors.

Step 3: Crane installation

A crane lifts each panel into position. Panels interlock with previously installed panels and the building structure. Installation is much faster than stick systems – up to 50-100 panels per day.

Step 4: Inter-panel sealing

Gaskets between panels create a continuous weather seal. No on-site silicone required for primary seals.

Step 5: Edge detailing

Corners, parapets, and building interfaces are completed – the most challenging areas.

Step 6: Testing

Water spray testing and air leakage testing as for stick systems.

Timeline: Unitised installation can progress at 1-2 floors per week – significantly faster than stick systems.

Read our office windows guide for related commercial glazing.

💰 Aluminium Curtain Wall System Cost Factors

Here’s what influences commercial glazing costs.

Typical cost ranges per square metre (installed):

• Basic stick system (standard double glazing): R5,500 – R8,000 per m²
• Stick system with thermal break + Low-E double glazing: R7,000 – R10,000 per m²
• Premium stick system (argon + Low-E + thermal break): R8,500 – R12,000 per m²
• Unitised system (premium): R10,000 – R15,000+ per m²

For a 10-storey building with 2,000m² of curtain wall, budget R11-20 million depending on specifications.

Read our cost guide for comparative pricing.

🧹 Maintenance & Longevity

Proper maintenance extends the life of your building envelope.

Quarterly maintenance:

• Clean frames and glass with appropriate solutions
• Check gaskets and seals for damage
• Clear weep holes and drainage paths

Annually:

• Inspect all sealant joints – reapply where cracked or separated
• Check for signs of water penetration – address immediately
• Inspect anchor connections for corrosion
• For coastal areas, check for salt damage – read our corrosion protection guide

Every 5-10 years:

• Professional inspection of structural connections
• Major sealant replacement (silicone has 10-15 year lifespan)
• Gasket replacement

Expected lifespan: Quality curtain wall systems last 30-50+ years with proper maintenance. The primary maintenance items are sealants (10-15 years) and gaskets (15-20 years).

Read our full maintenance guide.

❓ Frequently Asked Questions About Aluminium Curtain Wall Systems

✅ Final Thoughts: Curtain Walls Define Modern Architecture

After reading this guide on aluminium curtain wall systems, you understand why they’re the defining feature of contemporary commercial architecture.

Curtain walls transform buildings – flooding interiors with light, creating stunning visual impact, and providing energy-efficient building envelopes. But they’re complex systems requiring specialist design, engineering, and installation. Don’t treat them as oversized windows.

Work with experienced commercial glazing specialists who understand structural requirements, thermal performance, and weather sealing. Invest in quality materials – thermal breaks, Low-E double glazing, and proper gaskets. The upfront cost is significant, but the long-term benefits in energy savings, occupant comfort, and building value are substantial.

Key takeaways for curtain wall systems:

• Curtain walls are non-structural facades that hang from building frames
• Stick systems: affordable, on-site assembly, suited to smaller buildings (under 10 storeys)
• Unitised systems: factory-assembled, crane-installed, faster, higher cost (+20-40%)
• Thermal breaks are essential for energy compliance and condensation prevention
• Low-E double glazing recommended (U=1.8-2.2 for most commercial buildings)
• Costs: R5,500-15,000+ per m² depending on specification
• Proper installation is critical – water penetration is the #1 failure mode
• Expected lifespan: 30-50+ years with regular maintenance
• Use ServiceLink SA to find verified commercial glazing specialists

Your next step: Planning a commercial building with a curtain wall? Get free quotes from verified glazing specialists in your area.

For more information about commercial glazing, explore our related resources: shopfront guide, office windows guide, commercial doors guide, custom fabrication guide, and cost guide. Learn about our process on what is ServiceLink SA and why contractors join us. Find commercial specialists in your area: Gauteng, Western Cape, Johannesburg, Pretoria, Cape Town, and Sandton. For related services, see our building construction and CCTV guides.