What is curtain wall and storefront leak repair?
Storefront and curtain wall are aluminum-framed glass systems. Storefront is the lighter system used at ground-floor shop fronts, lobbies and entries, usually spanning one story and sitting on a sill at the floor. Curtain wall is the heavier system that hangs off the building's structure and runs past the floor slabs, often across several stories of an office building.
Neither system is meant to be perfectly watertight at the outer face. Both are designed to let a little water get past the outer seals, collect it inside the framing, and drain it back out through weep slots and sill receptors. Leaks happen when that internal drainage breaks down: gaskets shrink, joints open, end dams fail, or the weeps clog. Repair means finding which part of the drainage path failed and restoring it, ideally without pulling glass that doesn't need to come out.
Ordinary windows set into a wall are a different assembly. Those are covered under window and facade waterproofing.
How are storefront and curtain wall leaks repaired?
Know the system
Curtain walls are either stick-built, assembled piece by piece on site with pressure plates and snap caps holding the glass, or unitized, made from factory-assembled panels that interlock at stack and mullion joints. Some use structural silicone instead of exterior caps. Each type drains differently, so the specialist starts by identifying the system and, where possible, the manufacturer.
Test, don't guess
Leaks in glass systems are found with a calibrated spray nozzle, testing one joint at a time from the bottom up while someone watches inside. For curtain walls, industry field-test methods such as AAMA 501.2 describe this kind of nozzle testing. It shows exactly which mullion, horizontal or corner is letting water through.
Typical repairs
- Gasket replacement. Shrunken or brittle glazing gaskets leave gaps at corners. They're replaced, or corners are sealed with a compatible sealant.
- Pressure plate and cap work. Plates are re-torqued, damaged caps replaced, and joints between plate sections sealed.
- Sill receptors and end dams. Storefront sills need end dams sealed to the receptor, or water drains straight into the floor. These are a very common repair.
- Weep clearing. Blocked weep slots are cleared, and baffles are replaced where they're missing.
- Perimeter sealant. The joint between the frame and the surrounding wall or slab is cut out and replaced.
- Structural silicone joints. Failed weather-seal joints are removed and re-sealed with compatible silicone. Structural bonds are evaluated separately.
Repair or replace?
Most leaking systems are repaired, not replaced. Replacement makes sense when the framing is badly corroded, the gaskets and seals have failed across most of the building, or the system can't meet current performance needs. Even then, a thorough test program on a few typical bays tells the owner whether a targeted repair program can buy more years first. Ask for test results on representative bays before committing to a full re-glaze.
What are the warning signs of a glass system leak?
- Water on the floor along the base of storefront glass after rain.
- Drips from the bottom of mullions or the horizontal rails.
- Wet ceiling tiles just inside a curtain wall, at the floor-line joint.
- Gaskets pulled back at glass corners, or hanging loose.
- Missing or loose snap caps on curtain wall mullions.
- Weep slots that are painted over, caulked shut or packed with dirt.
- Wet carpet or swollen flooring at entrance doors and thresholds.
- Stains or corrosion on the inside face of the aluminum framing.
What causes curtain walls and storefronts to leak?
- Gasket shrinkage. Rubber glazing gaskets shrink back from the corners over time, opening a path at each one.
- Missing or failed end dams. Storefront sill receptors without sealed end dams let water run off the ends and into the floor.
- Frame corner joints. Joints where horizontals meet verticals rely on small sealant seals that crack as the frame moves.
- Blocked weeps. Painting, cleaning crews and well-meant caulking block the exits the system needs to drain.
- Unitized stack joints. Damaged or misaligned interlock seals between curtain wall panels leak at floor lines.
- Building movement. Slab deflection and thermal movement stress perimeter joints and splices.
- Door thresholds. Entrances sit at the lowest point of a storefront and need properly sealed thresholds and drainage.
Fogging between two panes of glass is a failed insulated-glass seal, not a leak into the building. It affects energy performance and looks, but water isn't getting inside. Mention it when you call so the right repair gets quoted.
What can you check before calling?
- Mark where water appears on the floor or ceiling, and which panel or mullion is directly above.
- Note whether it leaks in every rain or only in wind from one direction.
- At ground level, look at the bottom of the storefront frame for weep slots and check they're open.
- Look for gaskets pulled back from the glass corners on lower panels you can safely see.
- Check whether landscaping, a sidewalk or a planter slopes water toward the base of the storefront.
Pro tip: find the original drawings
Building or tenant improvement drawings often name the storefront or curtain wall system and manufacturer. That speeds up diagnosis and parts matching.
Warning: don't caulk the bottom of the frame
A bead of sealant along the outside of the storefront sill seals the weeps and traps water inside the system. It often makes interior leaks worse.
What happens during the glazing specialist's visit?
- System identificationStorefront or curtain wall, stick or unitized, captured or structural silicone, and the manufacturer if it can be found.
- Visual surveyGaskets, caps, perimeter joints, weeps and sill conditions are checked, inside and out.
- Nozzle testingJoints are tested one at a time from the bottom up to reproduce the leak.
- DiagnosisThe failed component is confirmed, along with whether it's isolated or repeats across the elevation.
- RepairGaskets, end dams, frame seals, perimeter joints or weeps are fixed at the source.
- Re-testThe same test is repeated to show the joint is now dry, with photos for your records.
What affects the cost of glass system repairs?
| Factor | Effect on the job |
|---|---|
| Height & access | Storefronts are reached from the ground, curtain walls may need lifts or swing stages. |
| System type | Unitized and structurally glazed systems take specialized repair methods. |
| Testing time | Large elevations take longer to test joint by joint. |
| Parts availability | Older systems may need custom or substitute gaskets and caps. |
| Glass removal | Pulling and resetting glass adds labor, and sometimes new glass. |
When is a glass leak an emergency?
Broken or cracked glass, a panel that has shifted in its frame, or a storefront letting in enough water to reach electrical outlets or merchandise all need fast action. Broken glass is a safety hazard first: board it or tape it off. For water pouring into the space, call for emergency commercial leak repair to get the opening secured and dried in.
Cracked overhead glass
Keep people out from under any cracked or loose glass above walkways until a glazier makes it safe.
Curtain wall and storefront FAQ
Why does water come in at the bottom of my storefront?
That's where the system collects and drains water. If the sill receptor is missing end dams, the weeps are blocked, or the perimeter seal under the sill has failed, the water ends up on the floor instead of outside.
Do the gaskets need to be replaced everywhere?
Not always. Water testing shows whether the problem is a few corners or the whole elevation. Isolated failures are fixed locally, while widespread shrinkage can justify a planned gasket replacement program.
Can curtain wall leaks be fixed from inside?
Some can, such as internal seals and some gasket work. Many exterior joints, caps and perimeter seals need outside access by lift, swing stage or rope access.
What is a sill receptor?
It's a channel at the bottom of a storefront that catches water draining down the frame and sends it out through weeps. Its end dams have to be sealed for it to work.
Is fogged glass a leak?
No. Fog between the panes means the insulated glass unit's seal failed. The unit should be replaced for clarity and efficiency, but it isn't letting rain into the building.
How do I keep the system from leaking again?
Keep weeps open, make sure painters and cleaning crews don't seal them, inspect perimeter sealant and gaskets regularly, and fix small failures before they spread.
Related services and areas
Curtain walls and large storefront entries are common on office buildings in North Creek and on campus-style buildings in Canyon Park. If your leak might not involve the glass at all, start with commercial water leak help in Bothell. Shops with kitchens behind the storefront should also see restaurant and kitchen leak repair.