How to Extend Roof Life

02/02/2015 |

Tips for roof repair and membrane maintenance strategies

Find, diagnose, and fix roof damage before it gets worse

By Janelle Penny

Premature roof failure – it’s the kind of challenge that keeps an FM up at night. This expensive nightmare isn’t just a money pit, it’s also the waste of a roof that could have endured many more years of service if it had been properly maintained.

That maintenance includes spotting the little problems before they turn into big ones so the roof can continue its long service life as planned. Try these four tips for keeping molehills from becoming mountains.

1) Understand Typical Damage
First, have an idea of what you might find once you access the roof. Certain types of damage are more likely in wet or cold months, for example, while others could be the consequence of a contractor accessing your roof to service an HVAC unit or install solar panels. These three common scenarios account for much of the minor damage you’re likely to spot.

Worker-inflicted: Contractors who access the roof can inadvertently damage it while they’re up there, particularly if they aren’t well-trained on preserving the roof. There are two main types of human-related damage, notes Heshmat O. Laaly, roofing consultant and author of Science and Technology of Traditional and Modern Roofing Systems. Dynamic damage happens when a worker actively harms part of the roof, for example, by dropping a tool that punctures the surface or spilling a chemical that eats away at the roof’s protective top layers. Static damage, by comparison, is caused by excessive pressure that causes deterioration below. “In both cases, reinforcement plays an important role,” Laaly notes.

In either case, it can be hard to identify the source of the damage if said contractor neglects to mention it. Owen Davis, technical specialist for Professional Roof Consultants, recommends maintaining a strict roof access management policy requiring everyone to sign in before accessing the roof.

“You need to know who goes up there, when they go up, what they’re doing, and where they are,” explains Davis. “That’s critical because if someone does drop or spill something and you find it later during a periodic inspection, you can go back to your roof access control log and say ‘We found damage in this timeline, and we know these HVAC guys were working on this particular unit at this time.’ That also helps cover costs for significant damage – you can show the log to the contractor.”

Storms and seasonal factors: Freeze-thaw cycles that cause materials to expand and contract can badly damage roofs, Laaly says. Rainstorms and other sources of water intrusion can impact insulation value in the short term; in the long term, it can contribute to the development of organic growth that can consume wood and lead to roof failure.

Wear and tear: It’s also vital to know how normal aging affects your roof system. Periodically examining your roof while the weather is cooperating will help you spot dried-out seams and other age-related deterioration before moisture intrusion becomes a problem, Davis says.

2) Stay Vigilant with Inspections
At bare minimum, you should inspect your roof for damage once or twice a year and repair as necessary, Laaly says. “Unfortunately, many owners think ‘out of sight, out of mind,’” he explains. “They don’t inspect the roof, so they miss issues that can lead to premature failure.”

Repair with the Right Materials

Making the right repair starts with knowing what kind of roof system is on your building, says Owen Davis, technical specialist for Professional Roof Consultants. Understanding what type of roof you’re working with will lead you to the correct repair materials. He recommends starting with these five simple questions.

1)  How old is my roof? Is it under a warranty?
2)  How steep is the roof slope?
3)  Is the roof smooth or does it have a grit-type texture?
4)  If it is smooth, what color is it? Is it slick or shiny?
5)  If it has a grit surface, is the grit from granules or rock?


Davis recommends quarterly inspections with general cleaning added to the spring and fall ones. The fall cleaning is especially important because falling leaves can clog troughs and drains and create ponding water.

“Once a quarter gives you an idea of what condition your roof is in and lets you spot any potential areas you need to address before the next season,” Davis explains.

Predominant failure locations vary by roof type, but typically include any junction where multiple materials meet, such as corners or pipe penetrations. For the most comprehensive inspection, however, Laaly recommends finding a NRCA-certified contractor who can examine potential trouble spots and recommend changes accordingly.

That contractor may also be required to maintain your warranty, so when it’s time to inspect the roof, consult the manufacturer’s requirements to ensure everything is done by the book. Any repairs for damage spotted during your inspection must be handled the same way.

“Roofing repair warranties drive a couple of things. First, they require periodic inspections, and if you’re not inspecting the roof you can void your warranty,” says Davis. “The warranty also requires that you call the manufacturer immediately if you have a water intrusion issue. You’re allowed to do temporary repairs to keep water from coming in until a warranty service agent can come out, but permanent repairs to meet the warranty must be done by an authorized repair contractor.”

3) Know Your Materials
The day to stock up on spare repair materials is not the day water starts coming through your roof. It’s important to be prepared in case temporary repairs are needed.

Make sure you know what material your roof is made of and what can be used to fix it. TPO and PVC membranes are especially tricky, Davis says – they look the same but are not compatible with each other. After you’ve verified what types of repair products are safe to use on your roof, it’s a good idea to have extras on hand for emergencies. These could include:

Plastic roofing cement: “This is available at any home improvement store, but make sure it’s for wet applications because quite often you’re going to apply this in a rainstorm,” says Davis. “It has chemicals in it to allow the plastic cement to adhere to a surface and seal the damaged area in an emergency.” Some cements can even seal when completely submerged, Laaly adds.

Polyurethane caulk or sealant: This can come in handy when water intrusion occurs at a penetration, Davis says. “Use caulk to seal around the jack and the pipe itself,” he adds. “Polyurethane is compatible with many systems.”

Self-adhering roofing tape: There is a wide spectrum of tapes on the market for different applications, so investigate and choose one that fits your specific needs. Look for one with a decent shelf life in case you don’t need the whole roll at once.

High-quality duct tape: As unlikely as it may sound, duct tape can be truly helpful in a pinch. “As you’ll be doing this in the middle of a storm, remember to dry off the membrane as best you can,” says Davis. “Take a blow dryer if you can, just to get the tape on there. You can even put some urethane in a split or a cut and then put the tape over it. That creates a good temporary seal that won’t void your warranty because the repair technician can remove the temporary products to do the proper repair.”

4) Avoid Common Mistakes
Knowing what materials are safe to use for your roof system goes a long way toward preventing mistakes, but there are still a few pitfalls that could trip you up. One common issue emerges with patches that have to be sealed with heat, Davis says: “Often people overheat the patch and end up cooking it by getting it too hot. It actually creates a bigger problem and damages the membrane.”

“The most important thing is to know, inspect, and maintain your roof system,” adds Davis. “Those three things will help your roof last. It costs you less in the long run to keep your roof maintained and serviceable than it costs for you to repair it.”

Janelle Penny is senior editor of BUILDINGS.


Membrane Maintenance for Modified Bitumen
How to achieve maximum longevity

By Heshmat O. Laaly

A roof that lasts as long as the building it
protects is the Holy Grail of building construction. But is it a realistic goal? The answer is yes – this long-lasting roof is achievable, albeit elusive. Examine these factors that are conducive to meeting this goal and find out if a high-performance roofing solution can meet your needs.

Influences on Longevity

When it comes to the longest-lasting roof systems, certain factors come into play. These include:

  • Geographical location
  • Exposure to weather, especially in climates with severe seasonal temperature fluctuations
  • Substrate type and condition
  • Building design
  • Functional attributes (e.g. extensive rooftop equipment, solar arrays, chemical effluents, or rooftop foot traffic)
  • Roofing material used
  • Quality of installer workmanship

The complexities of these considerations make it difficult to generalize about one uniformly ideal roofing specification, so the commercial construction industry remains dependent upon ASTM’s minimum standards as a performance benchmark. However, relying on this benchmark is short-sighted and has been damaging to the health of our industry, as evidenced by the average 17-year lifespan of today’s commercial roofs when they should be much longer. Aim for a roof system safety factor at least 20% higher than what ASTM requires; a threshold of 40% or more is not unreasonable and will help ensure the long-term success of the roof’s waterproofing.

The Proof Is in the Performance
One of the largest, most definitive studies of bituminous roofing membranes was conducted by the National Research Council of Canada in 1977. The objective assessments were made using a selection of more than 50 well-respected performance tests and revealed that performance of modified bitumen depends on:

  • The grade of bitumen used
  • The percentage of polymer used in the compound
  • Compatibility of the bitumen and polymer, as well as the dispersion consistency in mixing the two
  • The types of modifiers used (e.g. atactic propylene/APP, styrene butadiene styrene/SBS, styrene isoprene styrene/SIS, etc.)
  • The type and quality of fire retardants, fillers, and reinforcement scrim.

Given these findings, it’s no surprise that materials sharing identical generic descriptions and meeting the same ASTM and code standards achieve widely varying performance outcomes. Because the study was conducted nearly four decades ago, however, we recently selected a handful of still-performing leak-free roofs installed 23-29 years ago to confirm and update the research findings with real-world applications.

All three are located in Columbus, IN, which sits in a region of the state notorious for frequent freeze-thaw cycles that create rooftop conditions more challenging than average. Columbus temperatures range between 15-32 degrees F. for 64% of the year and between 85-100 degrees F. about 15% of the year. The roofs were installed on a variety of decks, including poured-in-place gypsum, wood, and metal, and were constructed with conservative specifications that called for mechanically attached insulation, a second course of mopped insulation, two plies of Type IV glass felts in hot asphalt and a modified bitumen cap sheet, dual-reinforced fiberglass scrim, and a flood coat of gravel in Type III asphalt.

In the case of one 25-year-old roof, I had the opportunity to review laboratory results on two core samples. The softening point of the asphalt used in the flood coat increased and penetration decreased compared to ASTM D312 Type III standard specifications, which is to be expected because asphalt ages through photo-oxidation and is accelerated by heat. Nevertheless, the system was solidly adhered with no evidence of gaps or voids. It remained pliable and watertight even though the asphalt had hardened with age.

The modified cap sheet, an SBS modified membrane reinforced with fiberglass, was removed from the base layers to verify its stability, low-temperature flexibility, and tensile strength. It turned out that the quality compound and the high-yield fiberglass reinforcement helped the membrane retain a remarkable 80% of its initial tensile strength, which meant it still exceeded the requirements of ASTM D6163 after a quarter-century of service.

Some hardening of the compound and reductions of overall tensile strength are inevitable, but these results demonstrate that high-performance materials promote compliance with industry specifications not just when the roof is installed, but throughout its extended service life. The continued waterproofing integrity suggests an excellent return on initial investment, meriting the serious consideration of any owner expecting to hold onto a property for 25 years or more.

Three Must-Dos for Extending Service Life
If extended service life is an appropriate goal for your roof, there is much you can do to improve your odds of long-term success. The three roofs studied have effectively doubled the life span expected of today’s commercial roof offerings thanks to these three common factors.

1) Specifying quality materials. All three roofs were on manufacturing buildings with higher-than-average foot traffic, which required systems with high puncture and tear resistance. Given the thermal variations in Indiana, a membrane with a generous safety margin in regards to elasticity and a reinforcing fabric with significant tensile strength were appropriate. In all three cases, the owner chose a bitumen blend of SBS polymers with a mixing process that ensured uniform dispersion, plus a high-performance scrim that added tensile strength several times greater than the industry standard in the early 1980s when the roofs were installed.

However, the membrane only tells part of the story. The specifications also called for a comparably high level of quality in all other system components, including two courses of insulation, multi-layered construction, a high-performance waterproofing cap sheet, and a belt-and-suspenders flood coat of gravel surfacing. Some may call these specifications over-engineered, but in my mind, the sustained performance of such redundant systems is attributable in no small part to the quality of the materials used.

2) Vigilant monitoring during installation. The highest quality materials can still result in a premature roof failure if they are improperly installed. Ensure every system component is added in full compliance with the specification and the manufacturer requirements. This means vigilant job site monitoring during construction is recommended – in the case of these roofs, this task was performed by a representative of the membrane manufacturer responsible for warranting the systems.

3) Long-term preventive maintenance. The final element indispensable to extending roof life is proactive maintenance. Roofing success is a responsibility shared by the building owner. No homeowner would expect a roof to survive multiple freeze-thaw cycles without cleaning out roof gutters periodically, and the typical commercial roof experiences far more foot traffic, exposure to potential punctures and tears, and degrees of building movement. Commercial roofs also support far more roof equipment, making preventive maintenance vital to long-term performance.

The owner of these three roofs collaborated with his roofing partners across decades for ongoing inspections of flashings, gutters, drains, and other critical components while diligently performing any required minor repairs. As a result, all three exceeded their warranted performance.

There can never be one single roof system application that solves every problem, but this approach to roof system selection, installation, and maintenance has already proved successful and cost-effective. If owners are to ever achieve a roof service life that lasts as long as the building itself, they must move forward grounded in these principles.

Dr. Heshmat O. Laaly is an analytical research chemist, professional roofing consultant, and president of Roofing Materials Science and Technologies in Los Angeles, CA. He is also the author of Science and Technology of Traditional and Modern Roofing Systems. For more information, see

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