What Is an Aluminum Storefront? | Commercial Glass Basics

An aluminum storefront is an aluminum-framed glazing system used for commercial building entrances and display windows, distinct from full curtain walls.

Walk past nearly any retail strip, bank branch, or medical office and you’re looking at one. Aluminum storefront systems form the transparent entrances and fixed-glass panels that let natural light flood commercial spaces while keeping the weather out. Understanding what these systems are matters if you’re planning a build, renovating a storefront, or specifying materials for a commercial project. The framing does more than hold glass — it carries structural loads, sheds water, and must flex as the building settles.

What Makes Up an Aluminum Storefront System

An aluminum storefront is a front-set, exterior flush-glazed assembly. The frame components are extruded aluminum sections joined to create a grid that holds insulated or monolithic glass. Industry specifications typically describe continuous jambs running vertically, with head, sill, and intermediate horizontals tied together using screw spline or shear block methods.

Material specifications commonly call for extrusions in ASTM B221, alloy 6063-T5 or 6063-T6. Finish-related sheet stock sometimes references ASTM B209 5005-H14 for anodized finishes and 3003-H14 for painted finishes, with minimum thicknesses stated in the project spec. The result is a durable, low-maintenance frame that accepts both fixed glass and operable doors.

• Front-set design — glass installs from the exterior, simplifying glazing and replacement.
• Continuous vertical mullions — carry wind load from glass to the building structure.
• Screw spline or shear block joints — connect horizontals to jambs and mullions.
• Thermal break options — available for projects demanding better energy performance.

Storefront Terminology vs. Curtain Wall

Storefront and curtain wall are not interchangeable terms, though they get confused constantly. A storefront system spans from the floor slab up to a structural header or lintel — typically one story tall. Curtain walls span multiple floors and hang entirely off the building structure, transferring wind loads at each slab edge.

That distinction drives cost, engineering, and performance requirements. A storefront carries lighter loads and uses smaller frame members, which is why it suits ground-level retail and office entrances. Curtain walls demand heavier sections and more complex anchoring because they span far greater distances.

Performance Specs That Matter

Contractors and architects verify storefront performance against ASTM standards. Air infiltration limits often cap at 0.06 CFM/FT² (1.10 m³/h•m²) when tested at 6.24 PSF (299 Pa) under ASTM E283. Water resistance gets verified through ASTM E331 testing, with the exact pressure differential set by project documents rather than a universal number.

Structural movement is part of the design conversation, too. The framing must accommodate story drift, twist, column shortening, long-term creep, and deflection without binding or breaking the glass seal. Specifiers match the storefront system to the building’s anticipated movement, not just its static dimensions.

One specification point that surprises newcomers: careful installers check weep holes before sealing. Several installation guides explicitly direct crews not to seal sill flashing weep holes, since those openings let trapped condensation and rain drain to the exterior.

How Aluminum Storefronts Get Installed

Installation follows a sequence that protects both the frame and the glass. Proper procedure starts with locating reference points from the general contractor’s benchmark or column centerlines, then measuring the opening at top, middle, and bottom. Installers use the smallest dimension and subtract clearance per the product guide before cutting frames.

Multiple frames get assembled on the ground first when the layout requires, then lifted into place and set plumb, square, level, and true. Glazing prep includes checking factory-installed intumescent tape on fire-rated units, placing setting blocks, and securing glazing beads and gaskets. Perimeter sealant closes the gap between frame and rough opening — except at weep holes.

Fire-rated storefront systems demand extra steps. The AluFlam installation guide, for instance, requires UL Listed fire caulking and mineral wool packing around the frame, specific to that rated assembly rather than general aluminum storefront practice. Shop drawings and project documents override general installation steps whenever a conflict appears.

Ready to compare door options for your project? Our tested roundup of the best aluminum storefront door choices covers what holds up in real commercial use.

FAQs