Curtain Wall, Cladding or Spider Glazing: How to Choose a Commercial Facade System

Introduction: Why Facade Choice Isn't Just Aesthetic

A building's facade is the single largest system decision that touches structure, energy performance, safety, and appearance all at once — and it's usually decided earlier in the project than most owners expect. Get it right and the building performs quietly for decades. Get it wrong and you're looking at water ingress, inflated HVAC bills, or a facade that simply can't be built to the drawings within budget.

"Facade and glazing" isn't one product — it's a family of systems (curtain wall, ACP and metal cladding, spider glazing, rainscreen systems) that get selected based on building height, budget, climate, and design intent, each with different structural, thermal, and fabrication implications. This guide walks through how those systems differ, the engineering that sits behind the glass, and what actually drives facade cost in India.

It also covers the parts of the scope that rarely make it into a design presentation but end up mattering just as much — aluminium doors and windows, architectural elements like canopies and railings, how facade specs should actually change across India's climate zones, and what ongoing maintenance a finished facade needs. None of it is exotic; most of it is simply decided early, rarely explained clearly to the owner making the call, and expensive to revisit once construction is underway.

What Facade & Glazing Covers

As a scope of work, facade and glazing typically spans:

• System selection and structural/wind-load engineering
• Glass specification — type, coatings, performance targets
• Shop drawings, fabrication, and material procurement
• Mock-up construction and performance testing (air, water, structural)
• Site installation, sealing, and weatherproofing
• Aluminium doors and windows, and architectural elements (canopies, skylights, railings)

It also has to be coordinated tightly with the building's structure and MEP design, since facade fixings interface with the structural frame and the envelope's thermal performance directly affects HVAC load calculations.

Choosing a Facade System

Curtain Wall Systems

Curtain wall is a structural glazing system where mullions and transoms — the vertical and horizontal frame members — carry glass or spandrel panels as the building's primary envelope, engineered against wind and seismic loads under IS 875 and IS 1893. It comes in three main forms: unitised (factory-built panels craned into place, faster on tall buildings), semi-unitised, and conventional stick-built (assembled piece by piece on site, more common on lower-rise or budget-constrained projects). See curtain wall systems for how system choice and mock-up testing work in practice.

ACP & Metal Cladding

ACP (aluminium composite panel), metal, tile, and stone cladding are rainscreen finishes fixed over a structural backup wall rather than load-bearing glazing — usually the lower-cost option for opaque facade sections, spandrel bands, and feature elements. Fire performance matters here specifically: ACP core material (FR/B1-rated vs standard polyethylene core) is a life-safety specification, not just an aesthetic one. See cladding systems and the ACP FR/B1 core glossary entry for what that rating actually means.

Spider Glazing & Frameless Systems

Spider glazing uses point-fixed stainless steel fittings — routels, tie rods, or a cable-net structure — to hold glass with no visible frame, typically for atria, lobbies, and feature entrances where an unbroken glass surface is the design intent. It's engineered per-project rather than off a catalogue system, which is reflected in cost. Details are in spider glazing systems.

Rainscreen Ventilated Systems

A rainscreen ventilated facade separates the weatherproofing (an outer panel layer) from the insulation and structure behind it with a drained, ventilated cavity — improving thermal performance and moisture management compared to a directly-fixed facade. It's more common on premium commercial and institutional projects; see rainscreen ventilated systems.

Aluminium Doors, Windows & Architectural Elements

Facade scope rarely stops at the glazed wall itself. Aluminium doors and windows — sliding, casement, and openable systems — sit alongside curtain wall and cladding as a separate but coordinated scope, usually specified with the same thermal-break and acoustic-rated glazing decisions as the main facade so the building envelope performs consistently. See aluminium doors & windows for system vs custom-fabricated options.

Frameless & Automatic Entrance Doors

Building entrances often get a distinct treatment from the rest of the facade — patch-fitted frameless glass doors, or automatic sliding entrances, both engineered for high-cycle daily use rather than the occasional operation a standard door hardware set is rated for. See frameless doors for how these are specified and installed.

Canopies, Skylights & Railings

Canopies, pergolas, skylights, and balusters are structural elements in their own right, not decorative add-ons — a canopy has to be engineered for wind uplift the same way the main facade is, and a skylight needs its own drainage and waterproofing detailing where it penetrates the roof plane. Railings carry their own handrail-load engineering requirement, whether fabricated in aluminium, stainless steel, mild steel, or glass. See architectural elements and railings for the engineering behind these details.

The Engineering Behind the Glass

Facade performance is specified in numbers, not adjectives. SHGC (Solar Heat Gain Coefficient) governs how much solar heat the glass lets through, which ties directly into HVAC load — see our commercial HVAC buyer's guide for how that load gets calculated on the other side of this decision. Low-E glass coatings and double-glazed units (DGUs) are the usual levers for improving thermal performance without changing the visible system.

Safety glazing is a separate, non-negotiable spec: laminated vs toughened glass determines how the glass fails (laminated holds together when cracked; toughened shatters into small, less dangerous fragments), and heat soak testing screens toughened glass for nickel sulfide inclusions that can cause spontaneous breakage months after installation. Structural connections have their own specification layer too — structural silicone glazing and thermal break aluminium sections both affect long-term performance in ways that aren't visible from the ground.

Two more details separate a well-engineered facade from an adequate one. The opaque bands hiding floor slabs and services between windows are spandrel glass, typically backed with insulation and finished to match the vision glass so the facade reads as continuous from outside — a detail that's easy to get visually wrong if it's not planned alongside the structural bay layout. And in a unitised curtain wall system specifically, the brackets connecting each panel to the building structure carry tolerances that absorb construction variance and building movement — undersized or poorly detailed brackets are a common source of water leaks that only show up after a few monsoon seasons, not during initial testing.

Aluminium finish is its own specification decision: anodising vs powder coating trades off cosmetic flexibility (powder coating offers more colour options) against long-term weathering performance (anodising typically holds up better against UV and salt-air exposure). And the physics behind a rainscreen ventilated facade — a drained, pressure-equalised cavity that manages moisture rather than trying to seal it out entirely — is worth understanding even for owners who ultimately choose a simpler directly-fixed system, since it's the benchmark ventilated systems get compared against on long-term weathertightness.

The Facade Delivery Process: Survey to Handover

Facade delivery follows a fairly fixed sequence: site survey and structural coordination, system design and engineering, a physical mock-up built and tested for air, water, and structural performance before full fabrication begins, fabrication and material procurement, then site installation and sealing.

The site survey step matters more than it sounds like it should. As-built structural dimensions on an actual building routinely differ from the architectural drawings by a few millimetres per floor — not enough to matter structurally, but enough that a facade fabricated strictly to drawing dimensions without a field survey can arrive on site not quite fitting. Unitised systems tolerate this better than stick-built ones, since each panel is adjustable within a bracket tolerance, but the survey step is what makes that tolerance sufficient rather than a gamble.

Installation itself typically proceeds floor by floor, working with the same crane or hoist logistics as the rest of the building's construction — which is why facade installation sequencing is usually planned jointly with the main contractor's tower crane schedule rather than independently. Working-at-height safety and temporary edge protection during installation are standard considerations on any facade site, not specific to any one system type.

Two things catch owners off guard here. First, imported glass, hardware, and specialised aluminium sections often carry long lead times — facade design and ordering has to start early, or it becomes the critical path on an otherwise on-schedule project. Second, mock-up testing isn't a formality: air, water, and structural performance are typically verified against ASTM test methods (E283 for air infiltration, E331 for water penetration), and it's the stage that catches a detailing or sealant problem before it's repeated across an entire building's worth of panels.

What Facade & Glazing Costs in India

System type is the single biggest cost driver: ACP and metal cladding is generally the lowest-cost option per sq m, unitised curtain wall sits above it, and spider glazing or custom rainscreen systems sit at the top because of the per-project engineering and fabrication precision they require. Within any system, glass specification (single vs double-glazed, coatings, performance targets), facade height and wind-load engineering, and the amount of non-standard fabrication (curves, oversized panels, custom mullion spacing) all move the number further.

As with office fit-out costs, itemized quotes against an identical system and glass spec are the only reliable way to compare facade contractors — a lower headline number often means a lower glass or hardware spec, not a more efficient fabrication process.

Facade Design Across India's Climate Zones

A facade spec that works in Gurugram doesn't automatically work in Chennai, and India's climate range is part of why. In hot, dry regions (much of Rajasthan and Gujarat), the priority is minimising solar heat gain — lower SHGC glass, external shading, and smaller glazing ratios all help keep cooling load in check. In hot, humid coastal cities (Mumbai, Chennai, Kochi), salt-air exposure pushes the finish decision toward anodised aluminium and more corrosion-resistant hardware, alongside the same low-SHGC glazing priority.

Composite-climate cities like Delhi NCR — hot summers, cold winters — need glazing that balances solar control in summer against heat retention in winter, which is where low-E coatings earn their keep more than in a purely hot climate. And in the limited cold-climate zones (parts of the Himalayan belt), the priority shifts toward minimising heat loss rather than heat gain — a genuinely different glazing specification, not just a smaller version of the same one. None of this changes which facade system to choose, but it changes how that system's glass and finish should be specified — which is why a facade designed generically and then "localised" late in the process tends to underperform one designed for its actual climate zone from the start.

Common Facade Mistakes & Risks

• Specifying glass performance (SHGC/U-value) after the HVAC load calculation is already locked, forcing a mismatch between envelope and cooling capacity
• Ordering long-lead imported materials late, turning the facade into the schedule's critical path
• Skipping or rushing mock-up testing, so a sealant or detailing flaw isn't caught until it's repeated across the whole building
• Treating ACP core fire rating as a cost line to trim rather than a life-safety specification
• Under-engineering wind-load and structural connections on tall or exposed buildings
• Choosing a finish (powder coating vs anodising) on colour alone, without weighing long-term weathering performance

Facade Maintenance & Long-Term Performance

A facade doesn't stop needing attention once it's installed and tested. Sealant joints have a service life — typically somewhere in the range of 15-20 years depending on exposure and sealant quality — after which resealing becomes necessary to maintain the weatherproofing the original mock-up testing verified. Planning for that maintenance access — gondola tracks, BMU (building maintenance unit) rails, or anchor points for rope access — is a design-stage decision, not something that can be retrofitted cheaply once the building is occupied and the facade is finished.

Warranty coverage is worth reading closely rather than assuming: structural glazing, weatherproofing, and glass unit warranties are often issued separately, by different parties (fabricator, glass supplier, sealant manufacturer), with different terms — and a facade contractor who owns the full scope end to end is generally easier to hold accountable than one coordinating warranty claims across three separate vendors after something goes wrong.

Choosing a Facade Contractor

Facade work sits at the intersection of structural engineering, fabrication, and site installation, so look for a contractor with in-house design and engineering capability (not just installation), a track record of mock-up testing to recognised standards, and coordination discipline with the structural and MEP teams — facade fixings and building services routinely compete for the same structural and ceiling space.

It's also worth asking specifically about fabrication capacity and quality control on the shop floor — a contractor without their own fabrication facility is effectively subcontracting the part of the job where fit, tolerance, and finish consistency actually get decided, which makes it harder to hold a single party accountable when a panel doesn't fit as drawn. And because facade projects routinely overlap with cladding, aluminium fenestration, and architectural elements on the same building, a team that can deliver all of it under one scope avoids the coordination gaps that show up at the seams between separately contracted systems.

Conclusion

Facade and glazing decisions get made early, are expensive to reverse, and quietly determine a building's energy performance for its entire life. Choosing the right system family, specifying glass performance deliberately rather than by default, and testing before full fabrication are what separate a facade that performs for decades from one that starts generating maintenance calls in year two.

Frequently Asked Questions

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Planning a facade for a new build or renovation? Hagerstone's in-house facade team handles design, engineering, fabrication, and installation for curtain wall, cladding, and spider glazing systems — see our facade & glazing services.