Structural Glazing

How structural glazing works

In conventional windows the glass sits in a frame and is held by a bead or a cap. In structural glazing the glass is bonded to the aluminium frame with structural silicone, a high-strength sealant designed to carry the glass's weight and the wind load. From outside, only glass and slim silicone joints are visible.

The aluminium sub-frame of mullions (verticals) and transoms (horizontals) is fixed to the building's slab edges or structure with brackets that allow adjustment and movement. Panels are then bonded on, and the joints between them are sealed with weather silicone.

There are a few ways to build it. Stick systems are assembled piece by piece on the building and suit low- and mid-rise work. Semi-unitised systems bond glass to frames in the workshop, then fix those to mullions on site, which gives better-controlled bonding. Unitised systems prefabricate complete panels and suit large towers.

Spider or point-fixed glazing is a different approach: glass held at its corners by stainless fittings on a steel or glass fin structure, used for entrance lobbies and atriums.

Glass specification: DGU, reflective and low-E

A glass facade lets in heat as well as light, and in a Gurugram summer that heat is expensive to cool. The glass specification controls it.

Toughened or heat-strengthened glass is used for strength and safety. Heat-strengthened glass breaks into larger pieces that tend to stay in the frame, which some designers prefer for upper floors; toughened glass is stronger. Laminated glass is used where glass is overhead or where falling glass would be a hazard.

Double glazed units (DGU) combine two panes with a sealed spacer and air or gas gap. They reduce heat transfer and road noise and cut condensation.

Reflective and solar-control coatings reduce the heat that comes through, and give the mirror-like or tinted look common on commercial buildings. Low-E coatings reduce heat transfer while letting through more visible light, so interiors stay brighter.

The right combination depends on orientation, building use and look. We discuss the options at the visit rather than choosing one glass for everything. A smaller glazed shopfront may instead suit a toughened glass shop front with door.

Where structural glazing suits, and what to check first

Typical projects are small and mid-size office buildings in Udyog Vihar and Sector 44 to 50 in Noida, showrooms along Sohna Road and MG Road, commercial complexes on Golf Course Extension Road, and lift and stair cores of residential buildings where a glass face adds light.

A few things need to be checked first.

Structure. The slab edges and beams must take the brackets, and their positions need to be surveyed so the facade can be set out true.

Approvals. Facade changes to a commercial building usually need the owner's or the association's approval, and some complexes specify glass colour or reflectivity.

Access. Glass panels are large and heavy; we plan for scaffolding, a mast climber or a crane, and for unloading space on a busy road.

Weathering. Pre-monsoon dust storms and heavy rain test every joint. Drainage paths behind the glass and the quality of the weather silicone decide whether the facade stays dry.

ACP often finishes the spandrels and edges around the glass; see ACP cladding and, for sun control, aluminium louvres.

What drives the cost of a structural glazing facade

Structural glazing is quoted after a survey; there is no published rate.

Facade area and height. Area sets the material; height sets access equipment and labour.

System type. Stick, semi-unitised, unitised or spider glazing.

Glass build. Single toughened, laminated, DGU, reflective or low-E coatings, and glass thickness.

Aluminium sections. Mullion and transom depth depends on floor height and wind load.

Silicone. Structural and weather sealants from established ranges, with the right primer for the frame.

Openings. Top-hung vents, doors or ACP spandrels within the facade.

Site logistics. Night working, road permissions for a crane, protection of the area below.

Of these, glass build and access usually move the figure most. A coated double glazed unit can cost several times a single toughened pane, and a crane on a main road brings permissions and fixed charges.

The written quote breaks these down line by line. For related cladding costs see the ACP cladding price guide.

Process and maintenance

Book a site visit for ₹99, usually within 24 to 48 hours, adjusted against the final bill if you go ahead. We survey the elevation, check the slab edges and access, and discuss the glass and system. A written, all-inclusive quote usually follows within about two hours of the visit and is valid for three days; on a large facade, we confirm details such as glass build before fabrication.

Work starts on a 50% advance. Brackets and mullions go up first, set out true; panels are then bonded or fixed and the weather joints sealed. Toughened glass production generally takes 7 to 10 days, and coated or double glazed units may take longer. The balance 50% is due on completion.

Clean the glass a few times a year with water and a mild cleaner, inspect silicone joints annually and reseal any that crack or lift. Other facade options are in the facades and shutters catalogue.