Storefront Glass or Curtain Wall: Which System Does Your Building Have?

Storefront glass is a framed glass wall that fits between the floor and the ceiling line of one storey, while a curtain wall hangs off the building's floor slabs and can span several storeys. Storefront suits street-level shops and entrances. Curtain wall suits taller buildings and moves with the structure. Know which one you have before you order glass or a repair quote, because it changes how the repair is done.

Storefront glass vs curtain wall: the short answer

Both are aluminum-framed glass walls. The difference is how they are built into the building. A storefront sits inside an opening. A curtain wall is hung on the outside of the structure.

Many buildings use more than one. A tower may have storefront at street level and curtain wall or window wall above. Check each elevation and each floor before you assume.

What is storefront glass, and what does storefront and glazing mean?

Storefront glass is the glass in a storefront system: a prefabricated or site-assembled aluminum frame that holds glass at a building's base. It usually includes the entrance doors, the sidelights and the transom glass above.

Glazing is the trade term for the glass, the frame it sits in, and the seals and gaskets that keep it weathertight. Commercial glass glazing covers insulated glass units (IGUs), safety glass and the framing around them. It is not the same as an ordinary window. A window is a single unit set into an opening in a wall. A storefront is a framed glass wall system, often with doors, that fills a large opening.

Safety glass is used where glass is near doors and walking areas. Tempered or laminated glass breaks differently from plain glass, and a permanent mark in a corner of the pane usually shows which type it is. Confirm requirements with a glazier and the building code before ordering a replacement.

The guide to aluminum storefront systems goes through the framing types and the storefront glazing guide for Kitchener-Waterloo covers installation and replacement.

How a curtain wall differs from storefront glazing

A curtain wall does not hold up the building. It hangs from it. Brackets fix the framing to the edge of each floor slab, so the glass and frame form a skin that can run across several floors. That is why curtain wall can reach higher and span farther than storefront.

• Anchoring. Storefront is fixed at the top and bottom of one opening, with no support in between. Curtain wall is held at floor slabs.
• Movement. Tall buildings flex, shift in wind and expand and contract with temperature. Curtain wall is designed to take that movement. Storefront is not meant for it, which limits how tall one can be.
• Construction. Curtain wall can be stick-built, with frames and glass assembled on site, or unitized, with large panels assembled in a factory and lifted into place. Storefront is usually assembled from smaller parts at ground level.
• Framing size. Storefront frames commonly have a face width of about 45 mm (1 3/4 in). Curtain wall mullions are generally deeper, sized to the span and the wind load.
• Water control. Both are meant to shed water, and both can leak when the sealant fails or the weep holes at the sill clog. Sealant at the joints needs periodic checking on either one.

The practical result: curtain wall is an engineered building envelope. Changes to its framing, anchors or large glass units usually need a design professional. Storefront is simpler and more forgiving.

Storefront vs window wall

Window wall is the third system, and it is the one most often confused with the other two. It is common in condo and apartment towers. Each pane or panel sits between a floor slab below and the slab above, so the edge of every floor shows as a band between rows of glass.

Compared with storefront, window wall is built for taller buildings but is still one storey at a time. Compared with curtain wall, it does not hang off the slab edge and does not run past floor lines. If you can see a floor slab edge or a spandrel panel at every level, you are probably looking at window wall. If you see long runs of glass crossing the floor lines, it is probably curtain wall.

Window wall adds a lot of joints and slab-edge sealant. Water control at those joints is a regular maintenance item. The gasket and seal replacement guide explains what failing seals look like at the glass.

How to tell which system your building has

You do not need drawings to make a good first guess. Walk the building and check these:

1. Does the glass stop at one storey? If so, it is almost certainly storefront.
2. Does glass run past the floor lines? If so, it is curtain wall.
3. Can you see the slab edge between rows of glass? If so, it is window wall.
4. How deep is the frame? Look at an open door or a section edge. Deeper frames, and mullions sized for long vertical spans, point to curtain wall.
5. Is there an opaque panel at each floor? A spandrel band is typical of curtain wall and window wall.
6. What do the records say? Original drawings, a spec sheet, the permit set or the installer's paperwork usually name the system and maker.

Take photos of each elevation and the frame in section, plus a measurement of the glass opening and any markings on the edge of the glass. Send them with your request. A glazier can often identify the system from photos, though some systems need a visit to confirm.

Thermal performance, cost and glass replacement

Each point below changes what you ask for, so it is worth knowing before you get a quote.

• Thermal performance. Aluminum conducts heat. A thermal break, a barrier inside the frame, reduces that loss. Older storefront from earlier decades may have single glazing and no thermal break. Newer systems of any type use insulated glass units. The Ontario energy code guide for storefront glazing covers what the code expects when you replace.
• Cost. Storefront is generally the lower-cost framing system. Curtain wall costs more because of engineering, anchors, access and glass size. Quotes differ most on access equipment, glass size and type, lead time and how much of the frame is touched. No price depends on the system name alone.
• Glass replacement. A storefront pane at grade can usually be replaced with ground-level access. Glass higher on a curtain wall or window wall may need a lift or swing stage. Large or structurally glazed units can need the manufacturer's process, not just a swap.
• Fogged glass. Fog between the panes means a failed IGU seal. The unit can often be replaced without replacing the frame, which applies to all three systems when the frame is sound.

Decide by condition. Replace the glass only when the frame, seals and anchors are sound. Replace the assembly when the frame is corroded, twisted or leaking. The guide to replacing storefront glass lays out the signs.

Before you order glass or a repair quote

A short checklist saves a second visit:

• Say which system you think you have, and which floor the glass is on.
• Send photos and the opening size. Note whether the glass is at doors or low to the ground.
• Say whether the issue is a crack, a fogged unit, a leak or a worn seal.
• Ask what access equipment the work needs, and what part of the walkway or lot it will close.
• Ask for the glass type in writing: tempered, laminated or insulated, and what the code requires at that spot.

D&D Commercial Services handles storefront glazing, aluminum-framed windows, insulated glass units and safety glass at doors and low glazing, and every job starts with a free written estimate listing scope, materials, timing and access plan. For curtain wall above grade or structurally glazed units, ask the first question early: whether the contractor handles that system. See the commercial windows and storefront glazing service for what is covered.

Storefront and curtain wall questions property managers ask

What is storefront glass?

Storefront glass is the glass in an aluminum-framed system at the base of a building, usually one storey high. It includes the glazing around entrance doors, sidelights and transoms. The frame is fixed at the top and bottom of the opening, so it suits street-level shops, lobbies and entrances, not tall glass walls.

What is the difference between storefront and window wall?

Storefront sits in one opening, usually at ground level, and is anchored at the head and sill. Window wall is used on taller buildings, with panels set between floor slabs so the edge of each slab shows. Both are one storey at a time, but window wall is built for towers and carries more joints.

Can storefront glazing be used above the first floor?

It can be, but storefront is designed for a single storey span with no support in between, so height is limited. Taller glass needs extra supports or a different system, and a design professional should decide. Do not substitute one system for another during a repair without checking.

Does fogged glass mean I need a new curtain wall or storefront?

Not usually. Fog between the panes means the insulated glass unit's seal has failed. The unit can often be replaced without replacing the frame. Frame damage, corrosion, leaks at the sill or failed sealant call for a wider repair, so have the frame checked when the glass is replaced.

Who can replace glass in a curtain wall?

Many curtain wall repairs need design input and special access, such as a lift or swing stage, and structurally glazed units may need the maker's process. Ask any contractor whether they handle your system before you book. Storefront at ground level is simpler and is a common glazing job.

Devon Moore, Operations Lead Founder & Operations Lead — D&D Commercial Services

Devon Moore is the founder and Operations Lead at D&D Commercial Services, delivering professional commercial property maintenance across Waterloo Region.