Commercial Roof Leak Repair: Finding and Fixing Leaks Fast

A roof leak in a commercial building is never just a nuisance. It is an active threat to your building's structure, your insulation's effectiveness, your interior finishes, your stored inventory or equipment, and in some cases, the health and safety of the building's occupants. When water finds its way through a commercial roof, the clock starts ticking immediately. Every hour of delay allows additional damage to accumulate, and what begins as a simple drip can escalate into a costly restoration project if not addressed promptly and professionally.

At Windward Roofing & Construction, we respond to commercial roof leak calls daily across the Chicago metropolitan area. Our 24/7 emergency repair service exists because we know from 40 years of experience that leaks do not wait for business hours and neither should the response. This guide walks you through the process of finding leaks, fixing them, and preventing them from occurring in the first place.

Common Sources of Commercial Roof Leaks

Understanding where leaks typically originate helps building owners and facility managers respond more effectively when water intrusion occurs. While every roof is different, certain areas are statistically more likely to develop leaks than others.

Flashing failures. Flashings are the metal or membrane components that seal the transitions between the roof membrane and vertical surfaces such as parapet walls, equipment curbs, pipes, and vents. These transitions are the hardest-working parts of any roofing system because they must accommodate thermal movement, vibration, and differential settling between horizontal and vertical planes. Over time, sealants crack, membrane flashings separate from the substrate, and metal flashings develop gaps at joints and corners. Flashing failures are the single most common source of commercial roof leaks, responsible for an estimated 70 to 80 percent of all leak calls our service teams respond to.

Membrane seam failures. On single-ply roofs like TPO and EPDM, the seams where membrane sheets overlap are potential weak points. Heat-welded TPO seams are exceptionally reliable when properly executed, but adhesive-applied EPDM seams can peel open over time, especially in areas subjected to stress from thermal movement or ponding water. Seam failures often manifest as long, linear leak patterns inside the building.

Punctures and physical damage. Commercial roofs endure foot traffic from HVAC technicians, satellite dish installers, window washers, and other service personnel. Each visit carries the risk of punctures from dropped tools, stepped-on fastener heads, or dragged equipment. Punctures through the membrane create direct pathways for water entry. Wind-blown debris, falling tree branches, and hail can also puncture membranes, particularly thinner gauge materials.

Clogged or damaged drains. When internal roof drains, scuppers, or gutters become clogged with debris, water backs up and ponds on the roof surface. Ponding water accelerates membrane deterioration, adds structural load, and can overflow through flashings and edge details that were never designed to handle standing water. Drain bowls can also crack or separate from the membrane over time, creating leak paths around the drain itself.

Deteriorated sealants. Roofing sealants and caulking are used extensively around penetrations, equipment supports, and expansion joints. These materials have a shorter lifespan than the primary roofing membrane, typically 5 to 10 years compared to 20 to 30 years for the membrane. As sealants dry out, crack, and shrink, they create gaps that allow water infiltration. Because sealant deterioration is gradual, these leaks often start very slowly and are difficult to trace.

Roof penetrations. Every pipe, vent, conduit, and piece of rooftop equipment that passes through the roof membrane represents a potential leak source. The more penetrations a roof has, the more opportunities for water intrusion. Penetrations added after the original roof installation, such as new HVAC units or plumbing vents, are particularly vulnerable if they were not sealed by an experienced roofer.

Why Leak Location Is Not Always Obvious

One of the most frustrating aspects of commercial roof leaks is that the point where water appears inside the building is rarely directly below the point where water enters the roof. On commercial roofs, water can travel laterally through insulation, along structural members, and through gaps in the vapor barrier before it finally drops through a ceiling tile or runs down a wall. This lateral migration can move water 20, 50, or even 100 feet from the actual entry point.

This means that simply looking at the roof directly above an interior leak stain will not necessarily reveal the source. Professional leak detection requires a systematic approach that considers the entire path water might take from the roof surface to the point of interior manifestation.

Professional Leak Detection Methods

When our service technicians respond to a leak call, they draw on multiple detection methods to pinpoint the entry point accurately.

Visual inspection. The first step is always a thorough visual examination of the roof surface, starting in the area generally above the interior leak and expanding outward. Trained inspectors look for open seams, cracked flashings, deteriorated sealants, punctures, standing water, and any other visible defects. Visual inspection identifies the source in a significant percentage of cases, particularly for obvious defects like open flashing seams or large punctures.

Infrared thermography. Infrared cameras detect temperature differences on the roof surface that indicate trapped moisture in the insulation below the membrane. Wet insulation retains heat longer than dry insulation after sunset, creating a detectable thermal signature. Infrared scanning is most effective on clear evenings after sunny days and can reveal the full extent of moisture infiltration, not just the entry point. This information is valuable for determining whether the insulation needs to be replaced in addition to repairing the membrane.

Flood testing. For flat roofs, controlled flood testing involves isolating a section of the roof with temporary dams and flooding it with a shallow layer of water while monitoring the interior below for signs of intrusion. This method is highly effective at confirming the general area of a leak but is limited to dry weather and requires careful execution to avoid overloading the structure.

Electronic leak detection (ELD). This method uses low-voltage electrical current to locate breaches in the roofing membrane. Because intact membrane is non-conductive and water is conductive, an electrical signal applied to the wet roof surface will be drawn to any point where water can reach the conductive deck below. ELD is extremely precise and can locate pinholes and other defects that visual inspection would miss.

Core sampling. Cutting small core samples through the roofing assembly allows inspectors to physically examine each layer, assess insulation moisture content, and check the condition of the structural deck. Core samples provide definitive information about the roof's internal condition and help determine whether a localized repair or more extensive work is required.

Temporary Leak Mitigation

While professional repair is always the goal, there are situations where temporary measures are necessary to protect the building's interior until a permanent fix can be executed.

Interior water management. The immediate priority when a leak is discovered is controlling the water inside the building. Place containers to catch dripping water, lay down plastic sheeting to protect flooring and inventory, and move sensitive equipment or materials away from the affected area. If water is pooling on a suspended ceiling, carefully puncture the ceiling tile to drain the water into a controlled container before the weight causes a section of the ceiling to collapse.

Emergency tarping. In severe situations where a large area of the roof is compromised, emergency tarps weighted with sandbags or fastened with mechanical anchors can provide temporary waterproofing until the weather clears and permanent repairs can begin. Tarps are a short-term solution measured in days, not weeks, and should be replaced by proper repairs as quickly as possible.

Surface patching. If the leak source is visible and accessible, a maintenance technician may be able to apply an emergency patch using compatible roofing cement, mastic, or self-adhering membrane tape. These temporary patches can slow or stop water intrusion in the short term but should not be relied on as permanent solutions. It is important to use materials compatible with the existing membrane, as some products can damage certain membrane types.

Permanent Repair Solutions

Professional permanent repairs are tailored to the specific cause and extent of the leak. The repair method depends on the roofing system type, the nature of the defect, and the overall condition of the surrounding roof area.

Flashing repairs and replacement. When flashing failure is the cause, the repair typically involves removing the deteriorated flashing material, cleaning and preparing the substrate, and installing new flashing using methods and materials consistent with the original system. For TPO roofs, new membrane flashings are heat-welded to the field membrane. For EPDM, adhesive or tape-applied flashings are used. In some cases, existing metal counter-flashings are also replaced or re-secured to ensure a complete, watertight detail.

Seam re-welding or re-adhesion. Failed membrane seams are repaired by cleaning the seam area and re-welding (for TPO) or re-adhering with compatible adhesive and cover strip (for EPDM). The repaired seam is then tested to confirm it meets or exceeds the strength of the original seam.

Puncture patching. Membrane punctures are repaired by cleaning the damaged area, applying primer if required, and bonding a patch of matching membrane material over the puncture. The patch should extend at least six inches beyond the damage in all directions to provide a reliable seal.

Drain repair or replacement. Leaking drain assemblies may require tightening and resealing of the drain clamping ring, replacement of the drain body, or rebuilding the membrane detail around the drain bowl. If the drain is recessed and the surrounding insulation is wet, the insulation must be replaced as well to prevent trapped moisture from causing continued problems.

Section replacement. When damage extends over a larger area, or when the insulation beneath a leak is saturated, a section of the roof may need to be cut out and replaced entirely. This involves removing the membrane and wet insulation in the affected area, allowing the deck to dry if needed, installing new insulation and membrane, and tying the new section into the surrounding existing roof.

When Repair Is Not Enough

Not every leak situation is best addressed with a repair. Sometimes the leak is a symptom of a roofing system that has reached the end of its useful life, and continuing to repair it is not economically rational.

Consider replacement over repair when leaks are occurring in multiple, unrelated locations across the roof. Think about replacement when the insulation is widely saturated, reducing its thermal effectiveness and adding weight to the structure. Evaluate a new roof when repair frequency has been increasing steadily over recent years, or when the existing roof has exceeded 80 percent of its expected service life. Replacement becomes the better option when the cost of accumulated repairs over the next three to five years would approach or exceed the cost of a new roof.

A professional assessment from a qualified commercial roofing contractor can help you determine whether continued repair or full replacement is the more cost-effective path forward for your specific situation.

Preventing Leaks Before They Start

The most cost-effective approach to commercial roof leaks is preventing them from occurring in the first place. A proactive prevention program costs a fraction of what reactive leak repairs, emergency service calls, and interior damage restoration cost over time.

Biannual professional inspections. Schedule comprehensive roof inspections in spring and fall to identify and address potential problems before they become active leaks. Professional inspectors examine every component of the roofing system and document conditions that require attention.

Quarterly drain maintenance. Keep all drainage components, including internal drains, scuppers, gutters, and downspouts, clear of debris at all times. Clogged drainage is the most preventable cause of commercial roof problems.

Sealant maintenance program. Inspect and renew sealants around penetrations and equipment on an annual basis. This small, routine expense prevents the slow, insidious leaks that sealant failure causes.

Controlled roof access. Limit and monitor access to the roof. Require all service personnel to use designated walkway pads, and inspect the roof after any third-party work is performed. Many punctures and damage incidents are caused by non-roofing contractors who are unaware of the precautions needed to protect the membrane.

Post-storm inspections. After major weather events, have the roof inspected promptly. Storm damage that is caught and repaired quickly causes far less secondary damage than storm damage that goes unnoticed for weeks or months.

Maintenance records. Document all inspections, maintenance activities, and repairs. Detailed records help identify patterns, support insurance claims, and satisfy warranty maintenance requirements.

Windward's Commercial Leak Repair Services

Windward Roofing & Construction operates a dedicated service department staffed by experienced technicians who specialize in commercial roof leak diagnosis and repair. Our service capabilities include 24/7 emergency response for active leaks, comprehensive leak investigation using visual, infrared, and electronic detection methods, permanent repairs using manufacturer-approved materials and methods, post-repair testing to verify the effectiveness of the repair, and detailed documentation for your records and insurance purposes.

We maintain a large inventory of common roofing repair materials so that most repairs can be completed on the first visit without waiting for special-order materials. Our technicians are trained on all major commercial roofing systems and hold certifications from the manufacturers whose products they repair.

If your commercial building is experiencing a roof leak, do not wait for the problem to worsen. Contact Windward Roofing for prompt, professional service. Our team will locate the source, implement an effective repair, and help you develop a plan to prevent future leaks.

Frequently Asked Questions