Water Leaks in Commercial Buildings: What to Do After Finding Them

Authored by J. Phil Wilbourn II, P.E., Director, Property Practice
Published April 5, 2023 | Updated July 1, 2026

Water staining appears on a commercial building’s interior ceiling after a rainstorm. The insurance carrier questions whether the water intrusion was caused by a storm-created opening. The building owner’s attorney argues if it wasn’t a storm-created opening, then it must have been caused by a construction defect. The contractor’s counsel points to deferred maintenance as the real cause.

Three parties. Same water damage. Three different theories of causation.

Water intrusion claims are among the most technically complex and frequently disputed losses in commercial property insurance. Determining where water infiltrated the building, how long the water had been infiltrating, and whether the water infiltrated the building through an opening that was created by a storm event, a construction defect, or a lack of maintenance often requires forensic investigation beyond what a standard inspection can provide. The distinction between a covered loss, a construction defect, and a maintenance-related condition may affect claim outcomes, litigation strategy, and liability allocation.

Firms like Rimkus offer forensic investigation and building envelope analysis to identify the origin, cause, and scope of water intrusion damage.

Key takeaways: Understanding water leaks in commercial buildings

Water leaks in commercial buildings can be difficult to trace because damage often appears far from the entry point. Recognizing common causes and warning signs may support earlier response.

What causes commercial water leaks

• Water may enter a building through openings in roofs, walls, or windows, or water may originate from plumbing or HVAC systems within the building, each requiring a different approach
• Sealants, flashing, and pipe connections may degrade over time, allowing water intrusion to occur years after construction
• HVAC-related condensation problems may mimic roof or wall leaks, complicating diagnosis

How to spot water problems early

• Ceiling stains, peeling paint, warped flooring, and white mineral deposits on surfaces may be indicators of moisture intrusion
• Musty odors and unexplained energy cost increases may signal hidden moisture
• Wet materials are generally recommended to be dried within 24 to 48 hours to help reduce the risk of mold growth

Rimkus provides multidisciplinary building assessment and water intrusion evaluation; contact us today.

What is a commercial water leak?

A commercial water leak generally refers to water entering a building or water/moisture developing within a building at an unintended location. In a house, a leak might mean water dripping from a pipe below a sink or water stain on the ceiling. In a commercial building, such as an office tower, retail center, warehouse, or apartment complex, leaks may be more complex because the buildings themselves are larger and contain more interconnected systems.

Water that enters through a small gap in an exterior wall, for example, may travel along framing members, through insulation, and behind interior finishes before appearing as a stain several rooms away from where it actually infiltrated the building envelope. The large distance between where the water enters and where the damage shows up is one reason the causation of commercial leaks can be difficult to determine.

Why commercial leaks are different from residential leaks

Commercial buildings typically have flat or low-slope roofs, larger window systems, more extensive plumbing networks, and industrial-scale HVAC equipment. These systems often interact in ways that make causation determination more complex.

Commercial buildings also involve more stakeholders. A building owner, property management company, multiple tenants, an insurance carrier, and several contractors may all have a role when a water/moisture problem surfaces. The more parties involved, the more important it becomes to understand exactly where the water is coming from and why.

Common causes of water leaks in commercial buildings

Water leaks in commercial buildings are often associated with several common categories. Understanding which type is involved matters because each behaves differently, produces different warning signs, and may carry different implications for insurance coverage and liability.

Roof problems

Roof leaks are frequently cited as a source of water damage in commercial buildings. Materials may degrade over time from sun exposure, temperature changes, and weather events. Seams between roofing materials can separate. Flashing, the metal or membrane strips that direct water away from joints and edges, can shrink, distort, or corrode over time, causing openings through which water can infiltrate.

Once water enters through these openings, it may travel a significant distance along the roof deck or structural members before dripping into the occupied space below. A ceiling stain in one part of the building does not necessarily mean the roof above that spot is the problem.

Wall and window failures

The building envelope generally refers to the components that separate the interior of a building from the exterior: walls, windows, doors, and the materials that seal the gaps between them. Over time, sealants can crack, shrink, or pull away as the building structure differentially settles or the materials expand and contract with temperature changes.

Among envelope components, windows are a commonly identified source of intrusion. The seals around the operable components or the flashing materials around the window frames may degrade after years of weather exposure, allowing water to penetrate during rain events, especially wind-driven rain that pushes water sideways rather than straight down.

Plumbing failures

Pipe corrosion, freeze damage, or long-term wear on supply or drainage lines may lead to leaks ranging from slow drips to sudden, high-volume failures.

Because plumbing leaks vary so widely in how they develop, an important distinction involves timing. A pipe that bursts suddenly during a freeze is a different situation from one that has been slowly corroding and seeping for months.

Heating, ventilation, and air conditioning (HVAC) issues

HVAC systems remove moisture from the air as part of the cooling process (condensate), routing it through condensate drain lines and pans. When those drains clog, disconnect, or pumps malfunction, condensate water may accumulate in or flow to unintended locations.  Also, condensation can develop on cold surfaces of HVAC supply ductwork in warm, humid spaces like attics or ceiling and wall cavities.

HVAC-related moisture damage can look similar to damage caused by roof leaks or wall failures, making it difficult to determine at first glance whether the source is the mechanical system or the building exterior.  For example, condensation dripping from supply air ductwork can cause ceiling stains that appear identical to a roof leak.

How to recognize the signs of water intrusion

Not every water problem announces itself with an obvious drip from the ceiling. Many commercial leaks develop slowly and leave subtle clues that building managers and occupants can learn to recognize.

Visible warning signs

Staining on ceilings or walls is one of the most obvious indicators. Brown or yellowish discoloration, especially in patterns that expand over time, may indicate recurring moisture. Peeling or bubbling paint, warped or buckled flooring, and swollen door frames can also indicate water accumulation behind finished surfaces.

Warning signs are not limited to interior spaces. On the exterior of a building, white, chalky deposits on brick or concrete surfaces may also indicate repeated moisture collection. Professionals call this efflorescence; it forms when water moves through masonry materials and deposits minerals on the surface as it evaporates. Efflorescence is not harmful on its own, but it may indicate that water is moving through the wall system.

Less obvious indicators

Musty or earthy odors, especially in enclosed spaces, may indicate hidden moisture or mold growth. The EPA notes that mold can begin growing on wet materials within 24 to 48 hours, so persistent odors should not be dismissed.

Unexplained increases in energy costs can also point to water problems. Wet insulation may lose some of its effectiveness, potentially requiring heating and cooling systems to work harder. A building where energy costs have risen without a clear explanation may have moisture issues worth examining.

The importance of early identification

Whether the signs are visible stains or unexplained cost increases, early recognition matters. Small leaks that go unaddressed tend to become larger problems. Water that sits behind walls or above ceilings may damage structural components, promote mold growth, and degrade insulation. These conditions are generally far more expensive to remediate than the original leak.

When damage does escalate, or when multiple parties disagree about what caused the problem, determining the source often requires more than a visual walkthrough.

How is water intrusion investigated?

When a water damage claim involves disputed causation, a standard inspection is rarely sufficient. Forensic investigation applies systematic methodology to help determine where water entered, how it traveled through the building, and whether the intrusion resulted from a sudden event or a long-term condition. Each step in the process is designed to produce documented evidence that support cause-of-loss determination in claims disputes or litigation.

Document and history review

Before visiting the building, forensic investigators typically review construction documents, maintenance records, previous repair reports, and/or prior claims history. This research may reveal patterns: recurring complaints about the same area, maintenance gaps that may have allowed small problems to grow, or previous repairs that may not have addressed the underlying condition.

Non-destructive assessment

Several technologies allow forensic investigators to evaluate moisture conditions without cutting into walls, ceilings, or roofs.

• Thermal imaging (infrared thermography) is used to detect temperature differences in building materials. The surface of materials with a higher moisture content will appear warmer or cooler than the surrounding dry materials under varying ambient temperature conditions, so thermal images can help identify areas that warrant further moisture investigation and help map pathways not visible to the naked eye.
• Non-intrusive (surface) or intrusive (pinned) moisture meters are used to gauge how much water may have been absorbed into materials like drywall, wood, masonry, or concrete. Systematic readings across an affected area can produce a moisture map showing where material moisture content appears highest. These readings can help indicate whether conditions appear more consistent with recent moisture exposure or a longer-term condition.

Controlled water testing

When the point of entry remains unclear, forensic investigators may apply water to specific areas of the building exterior using recognized protocols published by organizations like ASTM International and the American Architectural Manufacturers Association (AAMA). By introducing water to one section at a time and monitoring the interior for response, investigators can narrow down which component is contributing to water intrusion.

Targeted exploratory openings

In some cases, non-destructive methods cannot fully resolve the question of causation. Forensic investigators may make small, targeted openings in walls, ceilings, or roofing to examine concealed conditions directly. These openings can allow visual confirmation of moisture pathways, material deterioration, and construction details that may have contributed to the intrusion.

Exploratory openings are typically limited in scope and carefully documented through photography and written observations.

The tools and techniques used in these investigations continue to develop. Several recent advances have expanded what investigators and building professionals can assess, and how early they can identify problems.

What are some advanced technologies used in leak detection?

Several recent developments have made it easier to find problems earlier and with less disruption.

Thermal imaging cameras

• More sensitive and affordable, with some newer systems detecting temperature differences as small as a fraction of a degree

Drone technology 

• Equipped with cameras and thermal sensors allows rapid survey of large commercial roofs without requiring workers to access elevated areas

Building monitoring systems 

• Can track moisture levels, temperature, and humidity in real time, potentially signaling a developing leak before visible damage occurs

These advances support a more preventive approach to building maintenance and may complement traditional forensic investigation methods.

Protecting commercial buildings from water damage

Water leaks in commercial buildings are common, but they do not have to become costly surprises. Understanding the typical causes, recognizing early warning signs, and knowing when professional evaluation may be valuable can support more informed decisions about building maintenance and repair.

Rimkus provides building assessment and water intrusion evaluation services through multidisciplinary teams with expertise across architectural, structural, building envelope, and mechanical systems. For organizations seeking support with water-related building concerns, contact Rimkus to discuss specific needs.

Frequently asked questions

How does forensic investigation determine the source of water intrusion in commercial buildings?

Forensic investigators typically use a combination of non-destructive methods such as visual examination, infrared thermography, and moisture content testing and mapping to to help trace moisture pathways toward a probable origin.  Systematic water testing protocols can then be used to confirm the origin(s) of the water intrusion.  If required, destructive methods such as targeted exploratory openings may be used to determine whether the water intrusion resulted from design deficiencies, material failures, installation errors, or weather-related damage, which may be central to determining cause of loss.

Why is early evidence preservation important in water damage claims?

Water damage may alter or destroy physical evidence relatively quickly, potentially complicating root cause analysis if forensic investigation is delayed. Early documentation of moisture patterns, material conditions, and building system performance may help preserve findings that support accurate liability determination.