Facilities (Campus Spaces)

Is the Roof Leaking?

Leaky campus roof


Commercial roof leaks cost U.S. businesses billions of dollars annually, causing damage that ranges from unsightly water stains to life-threatening roof collapse. Common for institutional facilities, flat roofing systems are prone to leaks. Commercial roofs are typically very large with hundreds of feet of flashing membrane seams, numerous roof penetrations for equipment and complex drainage designs.

Failure to detect, identify and correct minor roof deterioration and leakage at the earliest stages is considered the greatest cause of premature roof failure. Costly roof repairs are often the result of design deficiencies or faulty application of the roof system. Furthermore, when properly designed and applied, all roofing materials can still deteriorate from exposure to weather at rates determined largely by the kind of material and the conditions of exposure. Even new roof designs that incorporate a waterproofing membrane are subject to potential climate damage.

There are numerous methods to detect water or moisture leaks in a commercial roofing system, but electronic leak detection (ELD) is the preferred, non-intrusive method. ELD is particularly helpful in identifying defects within millimeters of accuracy, providing targeted and effective repairs of the roofing system. ELD is also widely used to test the installation of a new roofing system to provide the building owner with peace of mind and confirm the roof system’s reliability.

Methods of Leak Detection

Finding a leak is not an easy task and there are several approaches for commercial roofs. The type of roofing system and how the building is constructed will largely determine the best methods for detecting leaks. Locating the source of the breach can be very simple, or can become a process of elimination involving multiple site visits from a professional roofing contractor. How a roof is built plays a large role in leak detection, as some roofs conceal the source of the leak more easily than others.

The following methods and devices can be used to detect roof leaks.

Visual Inspection

A visual examination requires a physical walk through of the building, both inside and outside, by a roof inspector. The roof inspector looks for obvious signs of damage, wear and failed installation. Roof leak inspectors look for telling signs such as discoloration, water stains and mold. Water stains often visually map the flow of water coming from the opening. Water may simply drip through a hole or enter the building, run across beams or trusses and drip some distance from the initial leaking point.

Visual inspections are cost-efficient and can be easily conducted several times throughout the year. A commercial roof leak inspector should have thorough knowledge of many types of roof systems and understand how other trade personnel can impact the integrity of the roof. A roof leak may be due to another aspect of the building envelope and not directly related to the roof installation.

roof replacement


HOW DO WE FIX THIS? Most facility managers prefer to replace an entire roof at a site rather than deal with each portion of the roof individually. While a larger order of magnitude would seem to cost less per square foot because of the cost of mobilization, the significantly lower costs of restoration offset the substantial costs incurred in the larger project.

Infrared Thermography

Infrared thermography, also called thermal imaging, is a non-destructive test method to detect and record temperature differences across the surface of the roof. This type of infrared detection has been around since the 1970s. Infrared thermography has grown in popularity in recent years because it is less invasive and affordable. Thermal scans are used to locate wet insulation, which is an indicator of a failing roof system. The infrared camera captures obvious temperature differences on rooftops. As the sun heats the roof, the wet insulation retains the warmer temperatures, and once the atmosphere cools, the infrared camera captures the thermal differentiation of the dry roof and wet insulation.

Infrared drones are another device that captures thermal imagery. Infrared drones are more expensive than infrared technology and produce similar results. This technology is particularly beneficial when inspecting a large building because it is quicker and allows the inspector to concentrate in more detail on the compromised area.

Infrared detection is optimal for conditions that provide distinct temperature differences between the interior and exterior of the building. The prime test conditions are at night after a sunny day and when temperatures cool quickly. The greater the rate of outside temperature change, the greater the difference in surface temperatures between the wet and dry areas.

Infrared thermography is not an ideal test method where there is ponding water or any precipitation within the last 24 hours. This test method only detects moisture in the top of the roof system, so if there are multiple roofs on the building and moisture is trapped in the lower roof, the scan will not detect the moisture. The lower roof cannot attain the heat it needs to be detected by the infrared scan. False readings can occur for roofs with ballasted systems, lightweight concrete decks and roofs with highly reflective surfaces.

Nuclear Scans

Nuclear scans use a nuclear gauge to detect various levels of hydrogen ions trapped within the roofing system. The readings displayed by the gauge are a measurement of the quantity of hydrogen ions that are present within a detectable area beneath the gauge. Since hydrogen ions are present in water, these readings can be correlated to moisture content once a baseline reading for a dry area has been established. A roof inspector will establish a roof plan before employing the nuclear scans to create a map of the wet areas. Areas with wet insulation will have a greater concentration of hydrogen ions than those with dry insulation.

Nuclear roof scans require a grid pattern, typically 5-foot-by-5- foot or 10-foot-by-10-foot squares. This type of leak detection technology can miss smaller areas of wet insulation because the actual readings are taken on a very small portion of the total roof. The readings only capture where the machine is placed, so if you set the machine one inch from the wet insulation, the machine will not detect it. Nuclear scans can be used on ballasted roof systems where other leak detection cannot be used. Nuclear scans of larger roofs require more time, and therefore are more costly. The scans can be performed during the day and are not affected by debris on the roof, winds or reflective roof coatings.

Electronic Field Vector Mapping

Electronic Field Vector Mapping (EFVM) is a leak detection method that will pinpoint the exact area of water entry. EVFM begins with a grounded wire loop around a given roof section, typically 5,000 to 20,000 square feet. The technician applies water as a conductive medium and one lead is connected to the wire loop and the other lead connects to the roof deck. Leaks are detected when the electronic current travels across the roof membrane and down through the breach in the deck. The technician will use two probes to determine the exact location of the leak.

EFVM is most often used on roofs where leak detection can be difficult due to ballasted single-pile roof systems or inverted roof membrane assembles. The suitability of EFVM depends on the electrical resistance of the waterproofing materials of the roofing system. Some waterproofing membranes vary in electrical properties, and some formulations may not be compatible.

roof installation


STAYING ON TOP OF IT. In a traditional roofing program, the in-house patch-and-repair teams or the contracted service teams are on call for leaks. This emergency response experience is sometimes rewarding (particularly for those on the team that can truly stop the leaks with one visit), but it is stressful for those that field the constant calls and complaints. Under a more strategic roof management plan the leak response teams do more preventative maintenance and less emergency response.

Maintenance and Prevention

Infrared thermography, nuclear scans and EFVM are all optimal, nondestructive ways to help find difficult roof leaks if the technician has been properly trained on how to operate the equipment. The equipment has become more affordable, but it can be costly to find a skilled technician who can perform the ELD technology successfully. Simply being proactive in leak maintenance can keep a building owner from spending extra costs for the ELD testing.

Additionally, a new roof does not mean that the commercial roofing system won’t encounter leaks or damage. Roof system maintenance is often the most neglected area of a building system. In order to extend the life of a roofing system, conducting roof inspections and minor repairs twice a year is recommended. Debris should be cleaned from the gutters and roof drains and penetrations and perimeters edges should be checked.

Scheduling routine commercial roof inspections and keeping a close eye on common problem areas will save significant costs with proactive management rather than paying for large-scale damage repairs and water cleanup.


While there are multiple causes of commercial and institutional roof leaks, water damage can be detrimental to the building envelope. Detecting the source of the leak can present another set of challenges for the building owner and it is highly advised that the building owner schedule a roof inspection with a trusted contractor. A highly skilled technician has the knowledge and training to launch an inspection to identify and repair the breach. Additionally, the technician will know what technology is best suited to pinpoint defects in the roofing membrane, enabling targeted and effective repairs.

This article originally appeared in the issue of .