They look alike from the sidewalk and are built completely differently. Which one a front needs is decided by height, support and water — not by looks.
If the glass is one storey tall and sits on the ground floor slab, it is a storefront. If it spans more than one floor or hangs off the edge of the slabs rather than sitting on one, it is a curtain wall. The names get used loosely on the street, but they are different systems with different engineering, and the wrong one in the wrong place is a leak or a failure waiting to happen.
| Feature | Storefront | Curtain Wall |
|---|---|---|
| Height | One storey, typically to 10–12 ft | Multi-storey, hung floor to floor |
| How it is supported | Sits on the slab; sill carries the weight | Hangs from the slab edges by anchors; spans between floors |
| Structural role | Infills an opening | Is the exterior wall |
| Profile depth | 1¾″ × 4½″ typical | 2½″ × 6″ to 10″+ |
| Glass sizing | Limited: 1″ IGU (12–16 oz frame max) | Unlimited: any light size up to crane capacity |
| Glazing method | Captured, from inside or outside | Pressure-plate, structural silicone, or unitised |
| Thermal assembly | On-site: frame then glaze (1–3 hours per section) | On-site (stick) or off-site (unitised): see below |
| Installation speed | Faster on-site (next-day occupancy possible) | Stick: slower on-site; Unitised: faster envelope close |
| Water management | Sill flashing and weeps | Internal drainage at every horizontal; rain-screen principle |
| Wind load | Low to moderate | Engineered per floor and elevation |
| Typical systems | Kawneer 451, YKK YES 45, Tubelite, Alutech | Kawneer 1600, YKK YCW, Cortizo, Alutech, Everest |
| Where we build it | Retail fronts, lobbies, ground floors | Corner elevations, full facades, multi-floor new construction |
| Relative cost per sq ft | Lower (simple frame, captured glass) | Higher (engineering, anchors, drainage, glazing) |
| Schedule impact | Longer: one storey at a time, 1–2 weeks per front | Stick: longer; Unitised: shorter (3–5 days) |
A storefront system is a frame of aluminum verticals and horizontals, about 4½ inches deep, that sits on the floor slab and fills an opening one storey tall. The sill carries the weight of the glass down to the slab; the head is fastened to the structure above but does not carry load. It is glazed from inside or outside with captured glass stops, and water that gets past the gaskets is caught in the sill and weeped out. It is the most economical way to glaze a ground floor and the right answer for every retail front, lobby and one-storey commercial entrance — 3915 Flatlands Avenue, Coney Island Avenue.
Glass sizing. Storefront thermal assemblies are limited by the frame width. Standard profiles are 1¾ inches wide, which can support a 1-inch insulated glass unit (two lites of tempered or annealed with an argon or air gap, total weight 12–16 oz per square foot). Thicker glasses, wider lites, or triple-glazed assemblies (1.5 inches total) require special oversized frames and heavier hardware, which negates the cost advantage. For large monolithic lites or any assembly thicker than 1 inch, curtain wall becomes the economical choice.
Assembly and speed. A storefront section (typically 3–5 feet wide) is assembled on site: mullions and rails are bolted together, the frame is plumbed and anchored to the structure, and then glass is captured and glazed. Each section takes 1–3 hours, including gaskets and bedding. A 20-foot retail front takes 1–2 weeks depending on access and coordination with the tenant. Next-day or same-afternoon occupancy is feasible if the frame and glass arrive together and the site is clear.
Limits. Above about 12 feet, the mullions are not stiff enough for the wind load, and storefront cannot be hung between floors because it has no way to transfer load to the slab edge. Push a storefront system past those limits and it deflects, the glass cracks at the corners, and the joints open.
A curtain wall is an aluminum grid, 6 to 10 inches deep, anchored to the edge of each floor slab and hanging in front of the structure — the "curtain." Each floor's section carries its own glass weight to its own anchors, so it can rise as many floors as the building has. The mullions are engineered for the wind load at that height and elevation; the anchors allow for the building moving and the aluminum expanding. Curtain wall is built in two fundamentally different ways: stick system (on-site assembly) and unitised system (shop-assembled modules).
How it works. A stick system is framed on site, storey by storey, piece by piece. Vertical mullions are anchored to the slab edge, horizontal rails are bolted between them, and then glass and gaskets are installed section by section. It resembles storefront in assembly method, but the mullion grid is engineered for multi-storey load and wind pressure at height, and water management includes internal drainage channels at every horizontal.
Advantages. Flexibility in changes: if a window size changes mid-job or a detail needs adjustment, the on-site frame can accommodate it without waiting for a new module. Easier access during construction if the building envelope is behind schedule. No shop lead time — mullions and glass can be ordered and installed as the building rises.
Disadvantages. Slower on-site installation (4–6 weeks typical for a multi-storey facade, frame then glaze). Requires skilled erection crews and ongoing site coordination. Quality depends on weather and crew execution; thermal performance can suffer if gaskets are installed in wet conditions. Higher labor cost because every lite is glazed on-site.
When to use it. Stick systems are preferred when schedule is secondary to budget or flexibility, when the building envelope is behind and you cannot wait for shop lead time, or when details are still being finalized. 24 Frost Street is a structurally glazed stick-system two-storey curtain wall; our crew glazed every lite on site with structural silicone.
How it works. A unitised system is fully assembled and glazed in the shop — one storey tall, three to five units wide, with gaskets, covers, and anchors ready. Each module is wrapped, craned to site, and anchored to the slab edge and to the adjacent modules. Glass is installed in the shop under controlled conditions.
Advantages. Fast site installation: 30–60 minutes per module, a 10-storey facade in 3–5 days. Consistent quality: every lite is glazed in the shop, so gaskets are clean, thermal breaks are properly seated, and pressure equalisation is verified. No weather impact on glazing. Reduces on-site labor and coordination complexity. Easier to schedule: once modules arrive, the work is predictable.
Disadvantages. Long shop lead time (4–8 weeks typical), so you cannot change specs after ordering. Premium cost per square foot because of engineering and the unitised production. Requires heavy crane access and detailed logistics planning. If a module is damaged in transit or a detail must change, the entire unit may need to be re-manufactured.
When to use it. Unitised systems are preferred when schedule is critical, when specifications are locked in, and when the building sequence requires fast envelope closure to protect interior trades. The Anable in LIC used shop-glazed unitised modules for its Cortizo envelope; the curtain wall was craned and anchored in days, not weeks.
Both stick and unitised curtain walls are drained at every horizontal member and pressure-equalised, so water that gets in is led back out at each floor rather than running down inside the system. That internal drainage is what lets curtain wall work forty feet up in a storm. The design is deliberate: multiple gaskets (inner and outer at each plane), test ports for pressure equalization, and upturned drip pans at every sill. The difference is execution: stick system drainage is installed on-site (weather-dependent), unitised is built into the module (controlled shop conditions).
The most common confusion is the two-storey front — a retail floor with offices or a mezzanine above, glazed as one plane. It is a curtain wall, or at least a heavier "storefront" series designed to span two floors with intermediate anchors. Ordinary storefront framing at that height is the mistake we are most often called to look at on other installers' work. The corner at 3915 Flatlands is storefront on the ground floor and curtain wall at the corner return for exactly this reason.
Storefront sits on the floor slab and fills a one-storey opening; curtain wall hangs from the slab edges and spans multiple floors as the building's exterior wall. Different depth, engineering, glass sizing, glazing method and drainage.
Ordinary storefront, no: it is not stiff enough and has no way to carry load to the slab edge. A two-storey front is a curtain wall or a heavy storefront series designed for it, with intermediate anchors.
Because load is carried through the mullion grid to anchors, not through frame width, any size lite fits the same profile. Storefront is limited to 1-inch assemblies and light lites; curtain wall can accept oversize lites, triple-glazed IGUs, and special glasses without redesigning the frame.
Storefront is faster on site (next-day glass occupancy is possible for a ground floor). Curtain wall: stick system takes 4–6 weeks for multi-storey facade (frame then glaze on-site); unitised takes 3–5 days for envelope closure (but 4–8 weeks shop lead time). The schedule depends on what you're optimizing for: occupancy time or construction sequence.
Stick system is framed on site piece-by-piece (slower installation, flexible specs, no shop lead time); unitised system is shop-assembled and craned in modules (faster installation, specs locked, long shop lead time). Both have the same on-site lead time for ordering; the difference is execution speed and flexibility.
Curtain wall, per square foot, because of the deeper profiles, engineering, anchors and drainage. Storefront is the economical answer wherever it is the right answer. Unitised curtain wall costs more than stick system due to the shop assembly and handling, but saves labor on site.
Storefront: Kawneer, YKK AP, Tubelite, Alutech. Curtain wall (stick and unitised): Kawneer, YKK AP, Cortizo, Alutech, Everest, Reynaers. Several brands make both, in different series.
Yes. Storefront repair — doors, closers, glass, leaks — is a large part of our work; curtain-wall repairs are usually glass replacement, gasket and pressure-plate work, and anchor inspection. Stick and unitised have the same repair methods.
Storefront Doors & Framing Curtain Wall Systems Storefront Repair Commercial Aluminum Systems Structural Glazing
About this page. Written by Alex GC Inc. d/b/a Alex Glass Construction and reviewed before publication by Aleksandr Chernovolenko, Managing Partner, with our design and estimating lead and a field foreman. Our foremen hold the NYC DOB Site Safety Training supervisor card and our crews the 40-hour worker card; we are certified to fabricate, install and service Alutech and Everest aluminum systems. Facts are drawn from our own projects, manufacturer test data and the applicable codes; where we are giving an opinion, we say so. Last reviewed September 2026. Credentials
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