When water shows up inside your commercial building during a storm, the first question is simple: who do you call? The answer depends on where the leak originates, what system is failing, and which trade actually knows how to fix it.
Start Here: Who to Call First for a Leaking Window
If you manage a commercial building and you’re dealing with water coming in around a window, storefront, or curtain wall during heavy rain, call a commercial glazier first. Not a roofer. Not a general contractor. A glazier who specializes in commercial windows understands the sealant systems, rubber gaskets, drainage channels, and framing details that control where water goes inside a window assembly, and a commercial glazing contractor like ONE Glass Service is built to find that source.
A reputable commercial glazier will inspect and test the system, then bring in or refer roofers or other trades if the leak source turns out to be outside the glazing. Before anyone arrives, prioritize safety: shut off power in wet areas, contain water pooling near electrical systems, and document the location and timing of the leak.
Quick decision guide – who to call:
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Commercial glazier: Water appears around the window frame, mullions, window sill, or glass panes; visible gaps in sealant or gaskets; foggy windows or failed insulating glass units
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Roofer: Water stains start above the window on walls or ceilings; leaks appear when snow melts off a flat roof or parapet, not during wall-level rain
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General contractor or envelope specialist: Multiple systems are involved (roof, cladding, windows), or the leak source is unclear and several trades need coordinating
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Maintenance staff: Only for minor issues like a single loose piece of interior trim that doesn’t involve the glazing system itself
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Call a professional immediately if mold growth is visible around windows, or if structural damage is present around the window frame
Common Causes of Window Leaks in Commercial Buildings
Understanding the causes of window leaks helps you choose the right contractor and avoid cycling through repeat repairs that never hold. Water can originate from the glass, frame, flashing, cladding, or roofline – not always where you’d expect.
Here are the most common sources of window leaks in commercial buildings:
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Damaged caulking and expired sealants: Perimeter sealants age, and old caulk allows water and wind to penetrate joints that once held tight.
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Failed gaskets: Rubber gaskets between glass and frame harden, shrink, or lose compression over time. When seals break down, water and air leaks share the same paths, creating both water intrusion and drafts.
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Clogged weep holes and drainage channels: Storefronts and curtain walls are designed with internal drainage paths. Channels blocked by paint, debris, or previous repairs cause water to pool inside the frame and overflow into the building.
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Improper installation: Improperly installed framing, flashing, or windows from older renovations create gaps that lead to persistent leaks. Poor installation is a frequent root cause that no amount of surface caulking will cure.
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Cracks in the frame or glass: Cracks in the window frame or glass panes create vulnerabilities for water entry, especially after hail or impact events.
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Structural or thermal movement: Metal frames expand and contract with Denver’s wide temperature swings. Over time, this movement opens joints and pulls sealants out of adhesion.
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Cross-trade sources: Compromised air and water barriers or cracks in stucco can cause water leaks around windows. Water can travel horizontally behind cladding before appearing at a window – making the window look like the problem when it isn’t.
Moisture from any of these sources can lead to mold growth inside walls and peeling or bubbling paint on interior finishes. If you see these signs, the leak has likely been active longer than you realize.
Who Handles What: Glazier vs Roofer vs General Contractor
Choosing the right trade saves time and prevents multiple ineffective service calls. Each trade has a defined scope, and understanding it keeps your window leak repair on track.
A commercial glazier handles everything within the glazing system – the window frame, glass, sealants, gaskets, pressure bars, drainage, and connections between the window and the surrounding wall. If you’re unfamiliar with how these assemblies work, understanding what a curtain wall is helps explain why these systems need specialized attention.
A roofer handles the roof membrane, parapet flashing, and roof-wall intersections, and is the right call when leaks originate above the window. Water damage restoration specialists handle significant moisture and mold issues after the source has been stopped. Exterior waterproofing specialists can fix leaks originating from wall cladding systems like EIFS or stucco.
When to call each trade:
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Trade |
Call When |
|---|---|
|
Commercial glazier |
Leak at or around the window, failed sealant or gaskets, foggy windows, water tracking on mullions, air infiltration around frames |
|
Roofer |
Water enters from above, parapet or roof membrane damage, leaks only during snowmelt from the roof, water on a second floor ceiling |
|
General contractor / envelope specialist |
Multiple systems failing, large-scale façade work, structural movement affecting glazing across multiple floors |
Structural damage around windows always requires professional evaluation – don’t leave it to guesswork.
How Commercial Window Leak Investigations Work
A leak investigation is a systematic process. It is not guesswork, and it is not someone showing up with a tube of caulk. When leaks keep returning, or when the visible signs don’t match an obvious source, professional diagnostics are the proper course.
The process starts with fact-finding: documenting where water appears inside, when the leak occurs (during heavy rain, wind-driven rain from a specific direction, or only when snow melts), and which elevation of the building is affected. Water stains on interior walls help trace the path water is traveling.
Next comes visual inspection – examining sealant joints around the window, glazing gaskets, frame corners, weep holes, and adjacent wall materials for visible signs of failure. A qualified glazier also checks for air leaks, which often share the same paths as water and confirm where seals have failed.
Then comes controlled water testing: applying water with calibrated spray patterns, starting at lower joints and working upward to isolate the exact leak path. This methodical approach prevents false positives and catches leak sources that show up far from where water appears inside. ONE Glass Service provides commercial leak investigation and diagnostics using this kind of structured testing.
Persistent leaks despite previous repairs signal a need for diagnostic capability, not another patch job.
Why “Just Caulking It” Usually Fails
Many maintenance teams try to fix leaking windows by squeezing more caulk into every visible joint. In commercial buildings, this approach usually fails – and sometimes makes things worse.
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It treats symptoms, not causes: If the window was improperly installed, if drainage channels are blocked, or if water is entering higher in the wall, new caulk around the window will not stop the leak. Failed caulking is often a symptom of a deeper issue, not the issue itself.
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It can block designed drainage: Over-caulking seals off weep holes and drainage paths that storefronts and curtain walls depend on. Blocking these channels traps water inside frames, leading to worse leaks and hidden water damage during the next storm.
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It creates a false sense of repair: A fresh bead of sealant looks clean, but if the underlying joint geometry is wrong or the old sealant wasn’t fully removed, adhesion fails quickly and the repair rarely lasts.
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Old caulk should be replaced, not covered: Proper sealant restoration means full removal of failed materials, redesign of the joint if needed, and confirmation that drainage and flashing still perform.
Sealant restoration is effective only as part of a complete repair plan. ONE Glass Service offers building envelope restoration services that address the full scope – not just the surface.
Repair Options: Reglazing, Targeted Repairs, or Replacement
Not every leaking window in a commercial building needs to be replaced. The right solution depends on what component has actually failed, and many leaks can be resolved without complete replacement.
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Reglazing: When the insulating glass unit has failed – condensation between glass panes, foggy windows, or a broken seal at the glass-to-frame joint – reglazing replaces the glass unit while keeping the existing metal framing. This is often the most cost effective path for seal failure at the glazing pocket. Learn more about choosing between reglazing versus full window replacement.
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Targeted repairs: Replacing perimeter sealants, reseating or replacing rubber gaskets, clearing clogged weep holes and drainage channels, reinstalling pressure bars, or repairing localized frame damage. These fixes work when the frame and glass are otherwise sound and only specific components have failed.
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Complete replacement: Necessary when frames show significant structural integrity loss, when recurring leaks span many openings, or when the system has reached end of life and repeated repairs no longer hold through extreme weather. New systems with modern framing and energy efficiency features may be warranted.
Hail events – common along the Front Range – can crack glass panes and deform frames in ways that open new leak paths. If your building has been hit, review the potential for hail damage to commercial windows before deciding whether to repair or replace.
Preventing Future Leaks in Commercial Windows and Curtain Walls
Prevention is part of routine building envelope maintenance for commercial buildings – not just a reaction after a storm. Regular maintenance can prevent costly window repairs and extend the service life of aging systems.
Practical maintenance checklist:
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Inspect windows at least once a year and again after major storms – look for visible gaps, damaged caulking, and movement cracks where different wall materials meet
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Replace failed caulk around the window perimeter before it lets water in
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Clear drainage channels and weep holes so water exits the frame as designed
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Check gaskets and weatherstripping for damage that allows drafts and air leaks
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Keep roof drains, scuppers, and gutters clear so overflow isn’t redirected toward window heads
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Verify that previous repairs have held through a full season of weather, including freeze-thaw cycles
Commercial buildings in Colorado and Wyoming see intense UV exposure at altitude, wide temperature swings, and frequent hail. These conditions accelerate sealant and gasket aging and can create new air and water paths if not monitored. Coordinated building envelope restoration – sealant replacement, metal restoration, and selective reglazing – can extend system life and reduce unplanned leak calls. A simple leak log noting dates, weather conditions, and locations helps professionals diagnose recurring issues more quickly.
When to Call ONE Glass Service for a Leaking Window
If you manage commercial buildings, storefronts, or curtain wall systems in the Denver Metro, Colorado, or Wyoming and your windows are leaking, ONE Glass Service focuses exclusively on commercial glazing.
Call when you see:
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Repeated leaks at the same window or on the same floor despite prior repairs
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Water stains or peeling paint around commercial windows
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Unexplained moisture near mullions, at the window sill, or along interior trim
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Drafts or air leaks around the window that suggest the same seal paths are compromised
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Leaks that move from floor to floor during heavy rain, pointing to systemic drainage or flashing failure
ONE Glass Service performs leak investigation, water testing, reglazing, sealant restoration, and building envelope restoration with minimal disruption to building occupants. No guesswork. Just the right solution for the actual problem.
Contact ONE Glass Service or call (303) 505-3194 to schedule a commercial leak investigation.