Quick answer: A curtain wall is the whole non-load-bearing glass-and-aluminium outer wall hung on the building; structural glazing is a method of fixing the glass in it using structural silicone instead of visible clamps. So the real choice is usually between a “capped” curtain wall (glass held by pressure plates with visible aluminium caps) and a structurally glazed curtain wall (smooth all-glass look with slim silicone joints). Structural glazing gives the cleaner look; capped systems are simpler and somewhat more forgiving.
What is a curtain wall?
A curtain wall is an exterior wall that carries only its own weight and the wind load on it, and transfers them to the floor slabs or columns through brackets. It does not hold up the building. It usually spans across floors and is made of:
- Aluminium mullions (vertical) and transoms (horizontal)
- Glass panes: toughened, heat-strengthened, laminated or double glazed units (DGU)
- Spandrel panels to hide slab edges: opaque glass, ACP or insulated panels
- Gaskets, sealants and drainage to keep water out
- Anchors and brackets fixed to the structure
Stick vs unitised
- Stick system: mullions and transoms are fixed one by one on site, then the glass is installed. Common for low and mid-rise buildings.
- Unitised system: complete framed glass units are made in a factory and lifted into place. Faster on tall towers, higher factory cost.
What is structural glazing?
Structural glazing (often called SSG, structural silicone glazing) bonds the glass to an aluminium sub-frame using structural silicone. The silicone carries wind load from the glass to the frame. From outside, you see no aluminium caps, only glass and narrow weather-sealed joints.
Types
- 4-sided SSG: all four edges bonded. Fully flush, all-glass appearance.
- 2-sided SSG: two edges bonded, two edges mechanically held. Shows horizontal or vertical lines of aluminium.
- Semi-unitised / unitised SSG: glass is bonded to frames in a controlled workshop and the framed panels are fixed on site.
Workshop bonding is preferred because cleaning, priming and curing can be controlled better than at height on a dusty site.
Side-by-side comparison
| Feature | Capped curtain wall | Structurally glazed (SSG) facade |
|---|---|---|
| How glass is held | Pressure plates and caps | Structural silicone bond |
| Appearance outside | Visible aluminium grid | Flush glass, slim joints |
| Critical workmanship | Gaskets, pressure plate torque | Surface prep, silicone application, curing |
| Glass replacement | Simpler | Needs re-bonding and curing |
| Tolerance to site errors | More forgiving | Needs accurate frames |
| Typical use | Offices, institutions, budget-sensitive work | Showrooms, corporate facades, premium retail |
Where spider glazing fits: spider (point-fixed) glazing is a third way of holding glass, using stainless steel arms bolted through holes in the glass, with no aluminium frame at all. It suits entrance lobbies and showroom fronts. See our guide on spider glazing for details.
What makes a structural glazing facade reliable
- Structural silicone of the correct grade, with bite and glue-line thickness calculated for the wind load and glass size.
- Compatibility checks between silicone, spacer tape, gaskets and the frame finish.
- Clean, primed surfaces and correct curing time before the panel is loaded.
- Separate weather silicone in the joints between panels.
- Safety glass: toughened, heat-strengthened or laminated, often heat-soaked.
- Mechanical safety retainers are often added on taller buildings as a backup.
Glass choices for South Indian facades
Our sun is the main design load after wind. For large glass areas:
- Solar-control or reflective glass cuts heat gain and glare.
- DGU (double glazed units) reduce heat and noise, useful for air-conditioned spaces on busy roads.
- Laminated glass for high-level panes over entrances and walkways.
- Spandrel areas in ACP or back-painted glass to hide slabs, beams and AC units.
On the coast, use corrosion-resistant fixings and anchors and inspect sealants more often, since salt and sun both age sealant faster.
Cost drivers (no guesswork)
Rates for both systems depend on:
- Aluminium section size and finish (powder coat or anodised)
- Glass type, thickness, DGU, coatings and heat-soak testing
- Structural silicone and weather sealant brands
- Building height, access and scaffolding
- Panel size and number of corners, returns and openable windows
- Engineering, bracket and anchor design
- Site location and logistics, plus GST
Aluminium and glass prices change over time, so a quote should be based on drawings and site measurement.
Which should you choose?
- Premium showroom or corporate face: 4-sided structural glazing, possibly with DGU.
- Office or institutional building on a budget: capped stick curtain wall.
- Double-height entrance or display front: spider glazing or SSG.
- Mixed facade: glazing where light is needed, ACP cladding on solid areas.
Openable windows and doors
Large fixed glass walls still need fresh air, smoke venting and access. Both systems can include:
- Top-hung or side-hung openable vents set into the frame, which should match the facade’s look from outside.
- Glass doors at entrances, often with patch fittings and floor springs, integrated with the curtain wall or spider glazing.
- Access panels for cleaning or servicing, where required.
Decide the number and position of openable windows before fabrication. Adding them later means remaking frames and glass.
Maintenance for both systems
- Clean glass regularly and plan safe access for cleaning at design stage, especially on upper floors.
- Inspect weather sealant joints yearly and before the monsoon.
- Check drainage holes in capped systems; blocked weep holes cause leaks inside.
- Look for any glass that has shifted or shows stress marks near edges.
- Keep the as-built details of glass sizes and types so any broken pane can be replaced quickly and correctly.
How Cladex helps
Cladex Elevations installs structural glazing and ACP cladding. The Zudio store on Trichy Road, Singanallur, Coimbatore, combines ACP cladding with structural glazing. Our engineers, Er. Sanjay M. and Er. Aravind M., look at your building’s height, orientation and use before recommending a system, and we list glass, aluminium and sealant specifications in the quote.
WhatsApp us your elevation drawing or a photo for a free, site-measured glazing quote.