Three Systems, Three Structural Ideas
Curtain Wall
A curtain wall is a non-load-bearing facade that hangs on the outside of the building structure. It spans past the floor slabs and is anchored to the slab edges, so the glass appears continuous over several floors. It carries its own weight and the wind load, transferring both to the structure through brackets, but it does not support the floors.
Window Wall
A window wall sits between floor slabs. Each storey has its own framed glazing assembly running from the top of one slab to the underside of the next. The slab edge is then covered with a cladding panel or a slab cover profile. From a distance it can resemble a curtain wall, but the horizontal band at each floor reveals the difference.
Structural Glazing
Structural glazing describes how the glass is held, rather than where the facade sits. The glass is bonded to the aluminium frame with structural silicone, so there are no external pressure plates or caps. The result is a flush, all-glass appearance. Structural glazing is most often used within a curtain wall system, either on all four sides or on two sides with the other two held mechanically.
Stick vs Unitised Curtain Wall
Curtain walls are built in two main ways.
Stick systems are assembled on site piece by piece: mullions are fixed to the slab edges, transoms are connected between them, and glass is installed into the grid. Stick systems suit low- to mid-rise buildings, irregular geometry and projects where site access is easy.
Unitised systems are factory-assembled panels, usually one storey high and one module wide, delivered complete with glass and lifted into place. Adjacent units interlock to form the joints. Unitised systems reduce work at height and suit towers where speed and quality control matter, such as high-rise projects in Dubai.
Comparison Table
| Factor | Stick curtain wall | Unitised curtain wall | Window wall | Structural glazing |
|---|---|---|---|---|
| Position | Outside slab edge | Outside slab edge | Between slabs | Glass bonded to frame (within a curtain wall) |
| Typical buildings | Low- to mid-rise commercial | High-rise towers | Residential towers, mid-rise | Landmark and premium facades |
| Site labour | High | Low (factory work) | Moderate | Depends on host system |
| Installation speed | Moderate | Fast once units arrive | Fast, floor by floor | Moderate |
| Design lead time | Shorter | Longer (engineering and mock-ups) | Shorter | Longer (silicone design and testing) |
| Appearance | Continuous grid | Continuous grid | Visible band at each floor | Flush glass, minimal lines |
| Replacing glass | From outside | From outside | Often from inside | Specialist re-bonding |
Cost Drivers (Without Prices)
We do not quote general prices, because costs depend on many project factors. The main drivers are:
- Glass specification: Low-E coatings, laminated layers, larger sizes and special colours
- Module size and repetition: many identical units are cheaper than many unique ones
- Engineering effort: wind load calculations, movement joints, thermal and condensation analysis
- Testing and mock-ups: performance mock-ups add time and cost but reduce risk
- Access and lifting: cranes, gondolas and scaffolding for installation and future maintenance
- Finish: powder coating versus fluorocarbon (PVDF) or anodised finishes
As a general pattern, a window wall is usually the simplest of the three, while unitised curtain wall carries higher engineering and factory costs that are offset on tall buildings by faster installation.
Performance in the Gulf Climate
All three can perform well in Oman and the UAE when correctly designed. Points to check:
- Thermal performance: thermal break profiles and double-glazed Low-E units reduce cooling loads
- Movement: the facade must accommodate thermal expansion from high surface temperatures, slab deflection and building sway in towers
- Water and air tightness: pressure-equalised joints and continuous seals; window wall needs careful detailing at the slab edge, where each storey meets the next
- Wind load: coastal and high-rise sites require engineered calculations
- Standards: curtain walling is commonly specified to EN 13830 in the region, alongside local authority requirements
Maintenance
- Inspect and replace sealants and gaskets at intervals recommended by the system supplier
- Check drainage paths at transoms and sills, particularly after dust events
- Plan façade access (building maintenance units or rope access) from the design stage
- For structural glazing, inspect structural silicone joints according to the supplier's programme
When to Choose Each System
- Window wall: residential and mixed-use towers where floor-by-floor installation from inside the building is practical, and where a visible slab band suits the design
- Stick curtain wall: low- to mid-rise offices, showrooms and hotels in Muscat and Dubai, podiums, and facades with irregular geometry
- Unitised curtain wall: high-rise towers where speed, quality control and reduced work at height outweigh longer design lead times
- Structural glazing: premium facades, showrooms and entrances where a flush, frameless look is part of the design intent
Alminyar Recommendation
Decide the facade type at concept stage with your architect and structural engineer, because it affects slab edge design, fire stopping and access. For mid-rise commercial buildings in Muscat, stick curtain wall or window wall usually offers the best balance; for towers in Dubai and Abu Dhabi, evaluate unitised systems early. Alminyar supplies stick and unitised curtain wall with thermal break construction and structural silicone glazing options, supported by wind load calculations and shop drawings.