What Is a Curtain Wall? Definition, Types & How It Works

How Does a Curtain Wall Work?

A curtain wall works by hanging a lightweight, self-supporting facade off the edge of each floor slab so the building frame carries the loads while the wall only resists the weather and wind. The framing grid of vertical mullions and horizontal transoms holds glass or opaque infill panels and is anchored to the structure with brackets at floor levels. Everything the facade experiences, from a monsoon downpour to a summer gust off the open Kokapet plateau, is resolved back into that structural grid.

• Dead load: the curtain wall's own weight is transferred to the slab through anchor brackets, typically at every floor (3-4 m spacing).
• Wind and seismic load: lateral pressure is resisted by the mullions and passed back to the structure; design wind pressure is derived from IS 875 Part 3 using local basic wind speed (about 44 m/s for Hyderabad).
• Water management: pressure-equalised rain-screen or drained-and-ventilated cavities channel any infiltrating water out through weep holes rather than into the building.
• Thermal movement: expansion joints and slip anchors let aluminium (which expands about 2.3 mm per metre per 100 degrees C) move without buckling or stressing the glass.

This load path is exactly what separates a curtain wall from a masonry or ACP cladding wall that sits on the slab. Getting the bracket design and anchorage right is the single most important part of any structural glazing job, which is why detailed shop drawings and facade consultancy matter so much on tall buildings.

What Are the Types of Curtain Wall Systems?

Curtain walls are classified mainly as stick-built or unitized, with further sub-types based on how the glass is captured. The choice depends on building height, project timeline, budget and site conditions.

• Stick system: framing members (sticks) and glass are shipped as parts and assembled piece-by-piece on site; lower material cost, ideal for low-rise and irregular facades but slower to install. See our stick curtain wall approach for mid-rise projects.
• Unitized system: factory-assembled, floor-height panels are craned into place and interlocked; faster erection, better quality control, and preferred for high-rise towers. Our unitized curtain wall line suits fast-track towers in the Financial District.
• Semi-unitized (frame-and-glass): mullions go up on site, then pre-glazed panels are added, blending stick flexibility with factory quality; see semi-unitized glazing.
• Structural silicone glazing (SSG): glass is bonded to the frame with structural silicone per ASTM C1401, giving a flush, frameless structural glazing appearance.
• Capture / pressure-plate glazing: glass edges are mechanically clamped by aluminium pressure-plate glazing caps for a gridded, robust look that copes well with heavy monsoon exposure.

Stick vs. Unitized: Which Should You Choose?

Choose a stick system for low-rise, budget-sensitive or irregular facades, and a unitized system for high-rise towers where speed, quality and weather-tightness matter most. The decision usually comes down to building height and how fast the site needs to be enclosed.

• Height: unitized systems dominate above roughly 8-10 floors because craning finished panels is safer and faster than scaffolding a tall tower for stick assembly.
• Speed: a unitized facade can be weather-tight within days of panels arriving, which is valuable on tight IT-park schedules around Gachibowli and Madhapur.
• Quality control: unitized panels are glazed and sealed in a controlled factory, so the critical structural silicone bonds cure under ideal conditions rather than in Hyderabad's dust and 40 degree heat.
• Cost and flexibility: stick systems have lower material and freight costs and adapt easily to odd geometries, retrofits and small facades, but need more skilled on-site labour and more site sealing.

For a boutique showroom or a four-storey office in Kondapur, a stick or office front glazing system is often the sensible pick; for a 20-storey tower, unitized almost always wins on total installed cost and reliability.

What Materials and Specifications Go Into a Curtain Wall?

A curtain wall is built from extruded aluminium framing, sealed glazing units, gaskets and sealants, each specified to defined dimensions and standards. Typical specifications include:

• Framing: aluminium alloy 6063-T6 extrusions, mullion depth 50-150 mm and face width 50-70 mm, powder-coated or anodised for corrosion resistance; custom profiles come from precision aluminium fabrication.
• Glass: single or double-glazed units 6-24 mm thick; toughened safety glass conforms to IS 2553 and laminated glass to IS 2553 Part 1.
• Insulated glazing unit (IGU): typically 6 mm glass + 12 mm air/argon gap + 6 mm glass, often with a low-E coating to cut solar heat gain; see our DGU facade options.
• Sealants: structural silicone (ASTM C1401) for bonding and weather silicone for joint sealing, both critical to long-term watertightness.
• Air and water performance: tested to standards such as ASTM E283 (air), ASTM E331 (water) and ASTM E330 (structural wind load).

For projects that want a sleeker skin, reflective glass facade coatings and spandrel glazing panels hide the floor slabs and services behind opaque glass while keeping a continuous glazed look.

How Does a Curtain Wall Perform in the Hyderabad Climate?

Curtain walls in hot Indian cities are engineered primarily to control solar heat gain and cooling loads while meeting the Energy Conservation Building Code (ECBC). In Hyderabad and Secunderabad, where summer temperatures cross 40 degrees C and monsoon brings driving rain and airborne dust, glass selection drives both comfort and long-term energy cost.

• U-value: a double-glazed low-E curtain wall achieves about 1.4-2.8 W/m2K versus roughly 5.7 W/m2K for single glazing.
• Solar Heat Gain Coefficient (SHGC): ECBC recommends a low SHGC (around 0.25-0.35) for hot climates to limit heat entering the building.
• Visible Light Transmittance (VLT): balanced to give daylight while controlling glare, often 40-60 percent.
• Energy savings: high-performance glazing can cut air-conditioning loads by 15-30 percent, supporting BEE star ratings and green-building goals.
• Durability: anodised or PVDF-coated aluminium resists corrosion and UV, giving a 30-50 year service life with periodic sealant maintenance.

Dust is the quiet enemy in Telangana. Recessed weep paths, quality gaskets and good drainage detailing stop grime from clogging the drainage cavity, and shading elements such as aluminium louvers or fins can cut peak solar load before it even reaches the glass.

Curtain Wall vs. Window Wall vs. Storefront

A curtain wall differs from a window wall in that it passes continuously in front of the floor slabs, while a window wall sits between them, floor to floor. This distinction affects structural behaviour, waterproofing and appearance.

• Curtain wall: spans multiple floors continuously, anchored to slab edges; best for tall, uninterrupted glass facades and the cleanest exterior lines.
• Window wall: installed slab-to-slab within each floor; simpler and cheaper but shows horizontal slab lines and needs careful slab-edge waterproofing.
• Storefront: a non-load-bearing glazed system for ground-floor and low-rise entrances, generally limited to about 3-4 m height; ideal for a toughened glass shopfront or retail frontage.
• Spider/frameless: for lobbies and atria, spider glazing and cable systems give an almost invisible glass wall where a full curtain wall grid is not wanted.

If your project is a single showroom or a ground-floor retail unit rather than a multi-storey tower, a storefront or showroom glazing package is usually more cost-effective than a true curtain wall.

How Much Does a Curtain Wall Cost in India?

An aluminium-and-glass curtain wall in India typically costs between INR 1,200 and INR 3,500 per square foot of facade area, with the final figure driven by glass type, system and performance grade. Understanding the drivers helps you budget realistically before design starts.

• Stick systems with standard single or basic double glazing sit at the lower end, roughly INR 1,200-1,800 per sq ft.
• Mid-range low-E double glazing on a good stick or semi-unitized system runs about INR 1,800-2,600 per sq ft.
• Unitized and structural silicone systems with high-performance IGUs and premium coatings reach INR 2,600-3,500+ per sq ft.
• Add-ons such as fritted glass, smart glass, fins, motorised louvers and complex geometry push costs higher.

Remember these are supply-and-install ranges for the facade only; scaffolding, cranage, structural steel brackets and edge waterproofing are usually additional. For an accurate, itemised estimate tailored to your building height and glass spec, request a facade quote and our team will size the system for you.

You can also browse completed towers, elevations and glass facades in our project gallery to see how different systems and glass choices actually look once installed across Hyderabad.

Common Problems and How Good Detailing Prevents Them

Most curtain wall failures trace back to water leakage, sealant breakdown or thermal stress, and nearly all are preventable with correct detailing and quality installation. Knowing the failure modes helps you ask the right questions of any facade contractor.

• Water ingress: caused by poor gasket seating or blocked weep holes; solved with pressure-equalised drainage design and clean, tested joints.
• Sealant failure: UV and heat degrade cheap silicone over time; specifying ASTM C1401 structural silicone and scheduling re-sealing every 10-15 years protects the bond.
• Thermal breakage: dark spandrel areas and shading edges can crack annealed glass, so toughened or heat-soaked glass to IS 2553 is used where thermal stress is high.
• Condensation and heat gain: single glazing sweats and overheats interiors; thermally broken frames and low-E DGUs, similar to thermal break windows, fix both.
• Air/water leakage at movement joints: slip anchors and correctly sized expansion gaps absorb the daily thermal cycling that Hyderabad's temperature swings produce.

Quality workmanship is what turns a good specification into a durable facade. Independent facade consultancy and factory-glazed unitized panels remove much of the on-site risk, which is why they are standard on major towers.