Professional specifications, installation guide & design solutions
In short: Curtain wall explained: stick-built vs unitized, pressure-equalised drainage, ASTM E283, E331 and E330 testing, thermal breaks and slab edge anchors. High-performance curtain wall systems for commercial buildings. Engineering and installation expertise included. Alex Glass Construction supplies and installs across New York City, Long Island and New Jersey from 7 Beach Street, Staten Island. Call 929-235-1233 or request a free quote.
High-performance curtain wall systems for commercial buildings. Engineering and installation expertise included.. Modern, efficient design with excellent weather protection. Perfect for residential and commercial applications, these systems are specified for the application rather than chosen from a catalog. Professional installation ensures optimal performance and longevity.
Facade and railing work is built fromsystem ranges rather than assembled from parts:
Send us the drawings and the design pressure and we will quote against what they require.
Proper installation is critical for optimal performance. Our installation team provides:
Installation includes sealing and flashing the perimeter of the opening, because a window is only as watertight as the junction between it and the building. Where an opening needs more than that — a failed sill, damaged masonry, a detail that was wrong to begin with — see waterproofing.
A curtain wall is a non-structural building envelope. It carries its own weight and the wind load acting on it, and transfers both back to the floor slabs — but it carries no part of the building's structure. It hangs off the frame like a curtain, which is where the name comes from.
That distinguishes it from storefront, which is a similar-looking aluminum and glass assembly but is designed to sit between floors at grade level and span far shorter distances. Specifying storefront framing where curtain wall is required is a genuine and expensive mistake, and it happens.
Stick-built systems arrive as individual mullions, transoms and glass, and are assembled in place. Lower material cost, more forgiving of dimensional variation in the building, and it suits smaller projects and irregular geometry. The trade-off is site labor, weather exposure during installation, and quality that depends on workmanship in the air rather than in a factory.
Unitized systems are built as complete panels in a factory, delivered finished and glazed, and hung from the slab edge. Faster on site, far better quality control, and far less scaffold time — which on a tall building usually outweighs the higher unit price. Panels interlock at the joints with a split mullion, so one of the great advantages is that inter-story movement is absorbed in the joint rather than fighting the frame.
The rough rule is that stick-built suits low-rise and complex shapes; unitized suits repetitive tall buildings where program matters more than material cost.
This is the part most often misunderstood, and it is worth explaining because it changes how a facade should be judged.
A properly designed curtain wall is not sealed against water on its outer face. It is a drained and pressure-equalised assembly. The outer line sheds most water; whatever gets past is collected in the glazing pocket and drained back out through weeps in the horizontals. The cavity behind the outer seal is deliberately vented so the air pressure inside it matches the pressure outside — because water is driven through a gap by a pressure difference, and if there is no difference, there is no driving force.
The practical consequence: a facade that relies on a continuous bead of sealant on its outer face to stay dry is badly designed. Sealant fails, and when it does there is no second line. Drainage paths must be kept clear during installation, and blocked weeps are a common cause of leaks on otherwise sound systems.
Curtain wall performance is not a claim, it is a test result. The relevant standards are ASTM E283 for air infiltration, ASTM E331 for water penetration under static pressure, and ASTM E330 for structural performance under uniform load. Dynamic water testing under AAMA procedures uses a propeller to simulate wind-driven rain rather than static pressure.
On significant projects the assembly is mock-up tested before production, and field testing to AAMA 502 or 503 checks the installed result. If a system is offered without test data behind the specific configuration, that is worth questioning.
Thermal break and condensation. Aluminum conducts readily, so the framing needs a polyamide or poured-and-debridged break separating inside from outside. Without it the interior mullion face runs cold and condenses in winter — on a large facade that is water running down the inside of the building. Condensation resistance is a separate rating from U-factor and worth asking about specifically.
Movement. Buildings move. Slabs deflect under live load, frames sway, and the facade expands and contracts through a temperature range far wider than the air temperature, as our waterproofing page explains. The system has to absorb inter-story drift and thermal movement in designed joints, not by stressing the glass.
Anchors and slab edge. Every load ends up in the anchor. Tolerance at the slab edge is the single most common source of trouble on site, because concrete is not built to the tolerance aluminum is made to. Adjustable anchors exist for exactly this reason.
Perimeter fire barrier. The gap between the slab edge and the back of the facade is a route for fire and smoke between floors, and it requires a tested safing system. This is a life-safety item, it is inspected, and it is not a detail to improvise.
Spandrel zones. The areas covering floor slabs and ceiling voids are opaque but still part of the facade. They need shadow box or spandrel panel treatment, insulation, and careful attention to heat build-up behind the glass.
Glass selection. Large areas of glazing make solar control the dominant energy question, which is where Solarban 60 or 70 earns its place. Anything above ground level should be considered for laminated and heat-soaked construction.
These describe the kind of work each area brings rather than any specific client project.
Repetitive residential towers — the classic unitized case. Floor plates repeat, the program is tight, and factory assembly plus fast hanging beats site labor comfortably. Wind pressure rises sharply with height, so the design pressure is the engineer's figure and drives glass thickness and anchor design.
The most demanding exposure in the region: high wind off open water, full eastern and southern sun, and salt. Pressure equalisation matters more here than almost anywhere, because wind-driven rain at pressure is exactly the condition a face-sealed facade fails under. Fixings and anchors want stainless of the correct grade.
Commercial towers, frequently with structurally glazed or point-supported elements where the glass itself carries load at the fittings. Large panes, expensive to replace, difficult to access — which is the argument for 100 percent heat soaking and for documentation proving it was done.
A mix of new towers and converted industrial buildings. Conversions are usually a stick-built or window-wall question, because the openings already exist and the structure is not built to a modern facade tolerance. New build on the waterfront is the same severe exposure as the Hudson side.
Smaller and more irregular projects where stick-built framing is the sensible answer and the energy code, rather than an architect's aesthetic, drives the glass specification. Often the honest advice is that the project needs storefront framing rather than curtain wall, and we will say so.
Send us the elevations, the design pressure from the engineer and any performance specification you have been given. We quote against what the drawings require. If a system has been named we will price it; if not we will tell you what the building needs, including when a simpler assembly would do the job. We work across Manhattan, Brooklyn, Queens, the Bronx and Staten Island, and throughout Northern New Jersey, the Jersey Shore, Philadelphia and the Lehigh Valley.
A curtain wall is a framed glass wall that hangs from the floor slabs and spans several stories, carrying only its own weight and wind load back to the structure. A storefront is a ground-floor assembly set between the slab and the floor above, usually one story tall. The two use different profiles, different anchors and different drainage, and a storefront system stretched to two or three stories is a common cause of leaks.
Stick-built curtain wall is assembled on site from mullions and transoms and suits smaller or irregular elevations and buildings where crane time is limited. Unitized curtain wall is built as factory-glazed panels, one story tall, and installed from the floor slabs; it costs more to engineer but goes up faster and gives better quality control on larger, repetitive facades. For most of the mid-rise work we see in Brooklyn, Queens and Jersey City, stick-built is the cost-effective answer; above roughly eight to ten stories, unitized usually wins.
The architect and the Department of Buildings will expect air infiltration, water penetration and structural test results for the system (ASTM E283, E331 and E330), the thermal performance of the assembly (U-factor and SHGC, usually from NFRC or a simulation report) for the energy code, and shop drawings showing anchors, dead-load and wind-load connections to the slab. We prepare the shop drawings and supply the system test data with the submittal.
By managing water, not by trying to stop it at the outside face. Pressure-equalized, internally drained systems let water that gets past the outer gaskets drain down the mullion and weep out at the transoms. The silicone seals at the sill, the end dams and the splice joints between mullion lengths decide whether the system works; most leaks we are called to fix are at those three locations.
Engineering and shop drawings typically take three to five weeks after the design is frozen. Extruded aluminum systems from European or Asian mills run twelve to sixteen weeks from approved drawings to delivery; North American systems can be faster for standard profiles. Installation on a mid-rise elevation runs several weeks depending on access and crane time. We give a dated schedule with every quote.
Yes, as a reclad or overclad. We survey the slab edges, check the existing anchors and the structure with the engineer, and design the new anchors around them. Many of the facade replacements we do in Manhattan and Brooklyn replace a failed 1970s or 1980s curtain wall or window wall with a new thermally broken system on the same slab edges.
We fabricate and install Reynaers, Cortizo and Alutech curtain wall from Europe, Everest aluminum, and factory-direct systems from several manufacturers we represent locally. We also install North American systems when the architect has specified them. Our shop in Staten Island cuts and assembles the mullions, and our own crews set the wall.
Across Manhattan, Brooklyn, Queens, the Bronx and Staten Island, on Long Island, in Jersey City, Hoboken, Newark and Northern New Jersey, and in Philadelphia and the Lehigh Valley in Pennsylvania.
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