Options for preventative roof maintenance

Tree growth on an inverted assembly.
Tree growth on an inverted assembly.

The testing equipment itself has evolved. Gone are the days when liquid nitrogen was required to cool down the IR camera. The equipment is now portable, light, hand-held, and may come with ‘wings’—drones. IR cameras secured to drones allow one to scan a roof from the safety of the ground, by pre-programming the device to fly a specific pattern. It is important to note federal government regulations require the registration of drones and trained pilots with a valid certificate. Additionally, drones are restricted to an altitude of 122 m (400 ft) above ground level, and must always be in the drone pilot’s line of site. Pilots must understand Canadian air regulations, including how to communicate with Nav Canada and local flight service station managers and read aeronautical maps. Further, there are specific limitations around when and if one can fly. Flying without approvals or putting aircraft or people at risk can result in a significant monetary fine ($25,000) and/or incarceration, as the rules are strictly enforced by both Transport Canada and the RCMP.

Electronic leak detection

Where thermography is restricted to BUR assemblies and requires ideal weather and environmental conditions, electronic leak detection (ELD) mechanisms can provide more flexibility in locating breaches in the membrane. This diagnostic method can be used on both built-up and inverted assemblies utilizing non-conductive membranes such as mod-bit, PVC, and TPO and light-coloured (white/grey) EPDMs.

ELD testing on black EPDM membranes will not be beneficial because their high carbon content makes them a conductor
of electricity.

ELD uses either low or high voltage power sources to create an electrical potential difference between the non-conductive roof membrane and the structural deck, which is grounded to the earth. If there is a breach in the membrane, the electric current will flow toward it, thereby allowing the operator to find the leak with reasonable accuracy.

Low-power ELD begins by laying down an un-insulated wire around the perimeter of the affected roof area. The un-insulated wire is subsequently connected to a pulse generator, and metallic equipment are grounded. Water is then applied to the roof membrane to create an electric field on the roof. By using two probes, and following the readings shown in the potentiometer, the location of the breach (ground fault) can be found.

High-power ELD uses a similar approach but without the need to wet the membrane. In this instance, one lead from the pulse generator is connected to the deck and the other is attached to a device looking like a ‘push broom’ with copper bristles.

The operator then walks the roof. As the push broom passes over a breach, the circuit between the grounding wire and copper bristles will be complete and register accordingly on the operator’s equipment, thereby identifying the location of the leak.

Roof sampling and testing

Depending on the situation and assembly type, localized water testing can be used. It can be followed by the insertion of probes or roof sampling (cut tests) to confirm the presence of moisture in the assembly. While probes only indicate the presence of moisture within the assembly, roof sampling give the added advantage of determining what is happening in the components beneath the membrane. For example, are the problems the result of roof failure or due to defects of underlying components?

Cut tests in any assembly should be undertaken by qualified roofing contractors, who can then proceed with the necessary repairs. Many roof membrane manufacturers mandate the use of only trained and approved roofing contractors on their systems. Failure to follow those procedures may result in a violation of warranty requirements.

Limited water testing is another tool to identify the source(s) of water penetration. When undertaking a water test, attention must be paid to minimize damage to the roof assembly or building interior, particularly when working over sensitive areas, such as hospitals (where infection control procedures may have to be considered) or data centres where damage as a result of a water test could have serious financial implications.

Limited water testing should not be confused with flood testing. Both the Canadian Roofing Contractors Association (CRCA) and the National Roofing Contractors Association (NRCA) do not advise flood testing. An advisory bulletin by CRCA’s national technical committee in March 2017 said they “do not support this practice, believing flood testing is not a reliable quality assurance method and that the risks associated with a flood testing far outweigh any potential benefits.”


In designing roofs, clients often request the inclusion of extended warranties in design documents, as many roofing membrane manufacturers offer 10- to 25-year schemes. Depending on the type, these warranties may cover the membrane only or the entire roofing system.

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