June 11, 2020
By Ted Katsoris
“Congratulations, Mr. Smith! We are sure you will like your new car. Now before you go, let us go over the owner’s manual, particularly the required maintenance.” This is a conversation many of us have had when purchasing a vehicle. Additionally, we make a mental note to take the car for the required service appointments. Why? Since we paid a lot of money for the car, we want it to avoid untimely repairs, and let us face it, we do not want to void the manufacturer’s warranty. Nowadays, cars come with little blinking lights to indicate low oil levels, prompting you to top up the tank in a timely manner.
Some of you may question why this article begins with a car maintenance reference—well, in the author’s experience, people spend more time on the upkeep of cars than roofs, which, in many instances, can be 10, 50, or over a 1000 times more expensive than a vehicle. Although roofs come with maintenance manuals, they do not have a dashboard with warning lights, and many owners only realize there is a problem after experiencing leakages or failures, which could have been prevented.
Although the roof is one of the most critical components of the building envelope, it can also be the most overlooked element. Deteriorated paving, spalled bricks, cracked precast panels, loose metal panels, failed windows, etc., can be seen from the ground with minimal effort. However, blocked drains, blisters, loose metal flashing, and deteriorated membranes go unnoticed unless one physically walks on the roof and undertakes a review. Left unchecked, these little problems can turn into expensive repairs, or in extreme cases, a roof failure.
A roof, regardless of its design, will be exposed to a variety of weather phenomena, including wind, torrential downpours, hail, snow and ice, airborne pollutants, and extreme heat and cold conditions. Exposed membrane assemblies, metal roofs, and roof shingles will also experience extensive (daily) temperature fluctuations that would impose undue stresses on the assembly.
Additionally, our feathered and furry friends may use the roof to rest or nest. For example, roofs located in northern climates can provide a temporary home to animals, as openings near mechanical units offer warmth during winter. Vegetative roofs also create a habitat for a variety of animals, some of whom may decide to become permanent residents.
Common maintenance items
A roof assembly may consist of a field membrane, tapered and base insulation, vapour retarder, and sheathing boards. Metal flashings, roof-mounted antennas, solar panels, and penetrations, such as roof drains, mechanical curbs, stack vents, roof anchors, and pitch boxes, complete the assembly. Manufacturers spend a considerable amount of time researching, engineering, and testing the various roofing components, hence, it is rare for them to simply fail. However, when a simple problem, as shown in Figure 1, is ignored, it is likely to result in extensive and expensive repairs.
The climate is changing. Over the last five years, Toronto (where the author is based) has experienced severe flooding due to prolonged periods of rain or sudden flash storms. At the time of writing this article, the city was under a weather alert—it was expecting 40 to 60 mm (1.5 to 2.3 in.) of rain followed by freezing rain, and 80-km/h (49-mph) wind speeds. In 2019, St. John’s, N.L., experienced a winter blizzard complete with 700 mm (28 in.) of snow and sustained winds at the speed of 120 km/h (75 mph). Water, ice, snow melt, etc., will find its way into a roofing assembly via openings.
The most effective approach to roof maintenance is prevention. This is accomplished by the owner proactively engaging specialized engineering consultants or qualified roofers who are capable of undertaking the necessary reviews and providing the appropriate short- and long-term recommendations. The reviews can be as easy as visuals or more advanced examinations such as thermographic roof scans, electronic field vector mapping (EFVM), water testing, and roof sampling.
The simplest and the most effective approach to preventative maintenance is to undertake a visual review of the roof. Using checklists, a professional walks on the roof and visually reviews the various components of the assembly. For example, many of the issues mentioned earlier can be easily identified during a visual review. Walking the roof enables consultants to ‘detect’ soft spots, an indication of deteriorated or moisture-laden components.
Some key items that would be covered in a visual review include:
Thermographic roof imaging
In the author’s opinion, the most common, non-intrusive investigation is thermal imaging. It can be used to detect both air leakage in the building envelope and thermal anomalies across the wall and roof assemblies. Depending on the location, thermographic roof scanning is conducted between late spring and late fall. A proper scan requires a cloudless day/night with little or no wind, dry surfaces, and daylight heating. Winds beyond 10 km/h (6 mph) will speed up the cooling of the roof and distort the cooling patterns. Standing water also poses another limitation. Additionally, exhaust fans and other equipment incorporating B-vents/chimneys will have to be turned off, as it may provide alternative thermal signatures that are unrelated to moisture.
In fundamental terms, the process involves the natural (sun) heating up of the roof assembly, and as the roof cools, areas of greater thermal mass (i.e. wet insulation) will retain heat longer than dry regions. The infrared (IR) camera measures and records the temperature differences of various objects on the roof by reading the emitted heat energy—hotter areas appear brighter with more vivid colouring than cooler zones.
Thermography works on built-up roof (BUR) systems where the insulation is ‘sandwiched’ between the deck and the roof membrane. It is also suitable for conventional modified-bitumen (mod-bit) membranes and fully adhered single-ply membranes such as ethylene propylene diene monomer (EPDM). Thermographic scanning of polyvinyl chloride (PVC) and thermoplastic olefin (TPO) roofs can be challenging, and require special attention due to the inherent sensitivity of light-coloured membranes.
Thermal imaging does have some limitations, as it cannot be performed on:
Thermographic scans can only be performed at night. It should be undertaken by people who are properly trained to use the equipment, interpret the onscreen images, and on safety issues. It is advisable to send two people to the site—one to use the equipment and another to record, mark the roof, and act as a safety spotter. A thermographic roof scan can only identify thermal anomalies. The presence of moisture within the assembly will have to be confirmed with a moisture probe or cut tests.
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
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.
Although these warranties are included in the price of the roof, they are not free; the owner is paying for them. The cost of extended warranties can vary from a few hundred dollars to thousands, and will depend on a variety of factors including the duration of the extended warranty, roof size, and if the client wishes to purchase wind riders (in excess of the standard 88 km/h [55 mph] in high wind zone areas).
These warranties are not a blank cheque for a new roof, as they come with specific clauses that have to be accepted by the owner before they become binding. One of these clauses includes the statement the building owner will have to maintain the roof and provide proof of maintenance. Failure to do so may result in the nullification of the manufacturer’s warranty.
Frequency and costs
The frequency of undertaking preventative roof reviews depends on the location of the building and the facility’s ‘importance.’ As a minimum, both CRCA and NRCA recommend preventative roof maintenance at least twice a year (fall and spring). Roof membrane manufacturers may have more stringent requirements with respect to the frequency of inspections.
The author advises it is best to conduct additional reviews following significant environmental events, such as flash downpours, extreme wind (including micro-bursts), hail, snow, etc.
While two visual reviews per year are enough for a typical building, the frequency may be increased based on the sensitivity of building use and components within the facility. For example, a water leak in a transformer station may shorten out electrical switching gear, and hospitals may have to take out rooms, as water damage my trigger infection control protocols, while a leak into a data centre may damage servers.
Although there is no standard (with respect to frequency), the author recommends a thermographic roof scan at least once every five years, as it may indicate a problem beneath the membrane that may not be visible during a visual review.
Who can undertake a review?
Walking on a roof can be hazardous, and therefore, property managers/facility operators are discouraged from undertaking roof inspections. In Ontario, the labour ministry requires personnel to have appropriate Working at Heights Training to access a roof, as owners can be held liable if there is an incident and an employee suffers an injury.
The author recommends retaining qualified roofing consultants to undertake these reviews as they are properly trained and knowledgeable about the nuances and typical failure modes of the roofing system(s) in question. Alternatively, owners may also seek guidance from the membrane manufacturer if the roof is under an extended warranty. One could also ask provincial or territorial roofing organizations such as the Ontario Industrial Roofing Contractors Association (OIRCA) for a list of their approved members.
Roofs are subject to very extreme physical and environmental conditions. They are, for the most part, the first line of defense against exterior elements, and, in many instances, the most neglected building element. Roof maintenance does not have to be a very complicated and time-consuming endeavour. With qualified people, it can be cost-effective and go a long way toward extending the life of a roof, as problems can be caught early and properly addressed.
However, failure to conduct proper maintenance will have a significant financial impact should an unscheduled roof replacement be required. In the author’s experience, replacement of the roof on a warehouse facility on the outskirts of a city—where there is appropriate ground storage—may cost between $215 and $280 per square metre ($20 and $26 per square foot), while an office tower located in the city core where materials will have to be taken to and from the roof via elevators may cost $690 to $780 per square metre ($64 to 75 per square foot). These costs do not include borrowing expenses, repairing any damages caused to the interior by leaks, or lost revenue in the event tenants have to be relocated. So, do we keep ignoring the car’s engine oil light?
Ted Katsoris is a practice lead in the Building Science Group of Building Specialty Services at Morrison Hershfield’s Markham, Ont., office. He has extensive experience in the fields of building science and building envelope repair/rehabilitation, as well as contract administration. Since joining Morrison Hershfield in 2004, Katsoris has overseen more than 800 projects. He brings more than 30 years of combined contracting and consulting experience to any project he undertakes. He can be reached at firstname.lastname@example.org.
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