Storefront Glazing: Why Ground-Floor Retail Leaks Differently

The sealant around a ground-floor storefront fails faster than identical sealant twenty floors up on the same building. Same product, same installer, same weather.

The reason is that upper-floor joints deal with weather, and ground-floor joints deal with weather plus everything that happens at street level. For anyone managing commercial property, retail frontage, or a mixed-use building with ground-floor commercial space, that difference should shape the maintenance schedule.

What a storefront system is

Storefront is a non-load-bearing glazing system installed at grade, typically spanning from the floor to the underside of the structure above, with entrance doors built into it. It is designed for ground-floor commercial use: large glass areas for display, door openings for customer traffic, and framing that can be configured around a retail layout.

It differs from curtain wall, which is a continuous skin hung on the outside of a building and running past the floor slabs. Storefront is generally lighter and shallower in section, and it is not designed for the same spans or wind loads. The distinction between glazing systems higher up a building is covered in the post on curtain wall versus window wall.

What matters here is that a storefront sits in the most physically demanding location on the building.

The five things attacking a storefront joint

Splash and spray. Rain hitting the sidewalk and road bounces back against the base of the frame. Vehicles passing a wet street throw water at ground-floor frontage. In winter that spray can carry road salt, which adds chloride to the mix. The base of a storefront receives water from below as well as from above, which no upper-floor joint does.

Door slam. An entrance door in a retail space cycles hundreds of times a day, and every closing transmits shock and vibration into the frame around it. Sealant joints near a door opening are worked constantly by that movement, which fatigues them far faster than joints in a static section of the same frontage. This is why failure almost always shows up first around entrances.

Physical contact. People lean on frontage, deliveries get wheeled against it, equipment is set down on sills, and signage gets installed and removed. Sealant joints at reachable height take mechanical damage that joints at height simply do not.

Cleaning. Commercial frontage gets washed frequently, and pressure washing is common on sidewalks and building faces at street level. High pressure directed at a joint can force water past a seal that would shed ordinary rain without difficulty, and repeated exposure damages the sealant surface. The distinction between appropriate cleaning pressures is set out in the post on pressure washing versus soft washing.

Thermal cycling at glass. Large glass areas facing the street heat significantly in sun and cool at night, and the aluminum framing moves with them. That movement works every joint in the system, in addition to everything else.

Why the base leaks most

Water in a storefront system collects at the bottom. Rain running down the glass reaches the sill. Splash arrives directly at the base. Water that enters the frame through the glazing pocket drains downward inside the framing.

A properly designed storefront expects this and handles it. The frame has internal drainage that carries water to weep openings at the sill. Sill flashing directs water out and away. End dams at the ends of the sill stop water running sideways into the adjacent wall instead of out through the weeps.

Each of those can fail or be missing. Weeps get blocked by sealant applied over them during a previous repair, by debris, or by dirt. End dams are frequently omitted at installation, which lets water travel along the sill and exit into the wall at each end. Sill flashing that slopes the wrong way or terminates short delivers water into the assembly rather than out of it.

When the drainage stops working, water that the system expected to shed accumulates instead and finds its way into the floor assembly or the wall.

Why the leak appears somewhere unexpected

Storefront leaks are often diagnosed late because the visible damage is not at the glazing.

Water entering at the base runs into the floor assembly at grade and travels. It appears as buckled or stained flooring, damp at the base of an interior partition, or discoloration at the slab edge, sometimes several metres from the entry point. A tenant reports a flooring problem, and the glazing is not part of the conversation.

The general principle applies here as everywhere in envelope work: the visible damage marks where the water came out, not where it went in, as explained in the guide on why leaks show far from the source.

When a ground-floor commercial space reports recurring flooring or base-of-wall damage near the frontage, the storefront sill deserves inspection before anything is attributed to plumbing or slab moisture.

The lease question

In a commercial building, responsibility for storefront maintenance depends on the lease, and it is worth establishing before there is a problem.

Commercial leases commonly assign the building structure and envelope to the landlord and the interior and fixtures to the tenant, but glazing and storefront are frequently addressed specifically and the allocation varies considerably between leases. Some put glass replacement on the tenant while keeping the frame and its seals with the landlord. Some assign the whole frontage to the tenant.

The practical problem is that an unresolved allocation delays repair. Water continues entering while the parties work out who is paying, and the damage grows. Establishing it in advance, and confirming who handles routine sealant maintenance as distinct from glass replacement, removes that delay.

For a strata with commercial units at grade, the same question arises between the strata corporation and the commercial owner, and the strata plan and bylaws govern it.

Repairing it properly

A storefront sealant repair is a normal sealant repair, done properly.

That means full removal of the failed material rather than a bead applied over it. It means cleaning both substrates back to sound, uncontaminated material, which at street level may involve removing accumulated grime, road film, and residue from previous repairs. It means priming where the sealant system requires it, installing backer rod to control joint depth and shape, and tooling the sealant to the correct geometry.

The reason full removal matters more here than elsewhere is that these joints move more. A cap bead relies on adhesion to the old sealant underneath, and at a joint being worked hundreds of times a day by door slam and thermal movement, that bond is the weak link. The comparison is set out in the post on caulking removal versus cap bead.

Material selection matters too. Joints at a storefront see movement, UV, and physical contact, and the chemistry chosen should suit that combination and be compatible with the substrates, including any coating on the frame. The trade-offs are covered in the guide on polyurethane versus silicone sealant.

While the sealant is out, the sill drainage should be checked. Clearing blocked weeps at the same time costs almost nothing and addresses the mechanism rather than only the symptom.

The scheduling advantage

There is genuine good news here. Storefront work happens at ground level.

No rope access, no swing stage, no roof anchors, no street occupancy permit for suspended equipment. A crew works from the sidewalk with modest staging. Compared to the access costs described in the post on rope access versus boom lift, storefront maintenance is among the least expensive envelope work a building has.

The constraint is business operations rather than access. Retail tenants need their entrances usable and their frontage presentable during trading hours, so work often runs early morning, evening, or on quieter days, and the entrance itself needs a plan for staying accessible during the work.

That is a scheduling problem, not a cost problem, and it is far easier to solve than getting a crew safely to the twentieth floor.

What to do

Inspect the frontage annually, more often than upper-floor glazing, because it deteriorates faster. Look at the joints around doors first, since that is where failure starts. Check the base of the frame and the sill. Look for blocked weep openings, which show up as water sitting in the frame after rain.

Watch for staining or damp at the interior base of the frontage, and treat recurring flooring damage near the glazing as a possible envelope issue rather than an interior one.

Keep cleaning pressures reasonable, and make sure whoever washes the sidewalk and frontage is not aiming high pressure directly into the joints.

And settle the responsibility question in the lease before a leak forces the conversation.

Storefront is the most abused glazing on the building and the cheapest to reach. Those two facts together make it the easiest envelope item to stay ahead of, and one of the most commonly neglected.

Sources and further reading

• American Architectural Manufacturers Association, storefront and entrance system standards, referenced 2026
• ASTM C1193, Standard Guide for Use of Joint Sealants, referenced 2026
• BC Building Code, Division B Part 5 (Environmental Separation), referenced 2026
• Canada Mortgage and Housing Corporation, Best Practice Guide: Glass and Metal Curtain Walls, referenced 2026
• Allweathercoating commercial frontage project records, Metro Vancouver, 2026