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Case Files: Silicone Roof Coatings

Friday, April 13, 2018

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By Fred Wolfe, GE Roofcoat

 

In the world of restoring roofs, there are many variables—so many, in fact, that when things don’t work out as planned, it can be quite a challenge to diagnose the problem and properly decide on a corrective course of action.

All photos courtesy of GE Roofcoat

When the samples arrived, one of the ways we assess the film is to view it on a light table. This helps us to determine the consistency of the application and also view any pin-holing that may have occurred.

Mistakes happen, and every manufacturer, specifier and contractor has had to deal with some level of unplanned events. When a problem arises on a roof coating project, there are actions that can be taken from the beginning to minimize the difficulties, while also keeping in mind the best interests of all parties involved. Here are three examples of difficulties with silicone roof coatings, and how they were discovered, diagnosed and solved.

 

CASE NO. 1: THE PEELING COATING

We got a call claiming, “Your coating is peeling from our concrete roof, and we don’t know what went wrong!” We asked the customer for some initial information, which is customary for any responsible manufacturer. We asked for the batch number of the product applied, the age of the project and for pictures of the problem. The customer provided all of these, and also sent us some samples of the peeling coating for our examination.

It is customary for responsible coating manufacturers to keep samples, also known as “retains,” to test in the future should problems occur in the field. We checked the retains for those batch numbers, and found all of that material to be well within the quality control specifications.

When the samples arrived, we employed one of the ways we assess the film: viewing it on a light table. This helps us to determine the consistency of the application and also view any pin-holing that may have occurred.

Through the light table examination, we noted that the application rate was consistent with the specification. On the other hand, we also noted the presence of a large number of pinholes. Since this is not a common occurrence for the product, is was worth taking a closer look. Through the use of a microscope, we observed that the pinhole shape was consistent with what is observed when water vapor pressure builds and then bursts through the film.

Through the use of a microscope, we observed that the pinhole shape was consistent with what is observed when water vapor pressure builds and then bursts through the film.

The underside of the same pinhole reflected a “pressure channel,” where water vapor pressure caused a fissure in the film. Due to the consistent nature of the pinholes, it was determined that the cause of disbondment was a wet substrate. Pinholes only occur when the coating is still curing and is in a liquid state; they do not occur months or years later.

When this was explained to the customer, it was agreed that the best course of action was to strip the remaining roof coating from the concrete, apply a vapor-blocking primer and then reapply the coating. We then used this opportunity to retrain the customer about the proper methods for testing the moisture level in concrete. We recommended that a pin meter or a calcium chloride test be utilized to determine moisture content in concrete. When that was complete, and the primer and coating were re-applied, the project was a success.

 

CASE NO. 2: THE CURIOUS BURN MARKS

We received a notification from one of our contractors that, during a regular maintenance inspection, a building owner noticed some dark brown marks in the middle of their silicone-coated roof. He wondered if these marks could be made by cigarettes; however, because of the size of the marks, this was unlikely. He was worried that the silicone around those areas might be compromised and wanted to address the problem while it was very small. After reviewing the pictures, we determined that a site visit would be necessary to determine what might be the cause of these brown blemishes.

When inspecting any roof, it is important to thoroughly walk the entire surface, not just the areas of concern. A serpentine pattern works well and allows the inspector to see all areas of the roof from multiple angles. We noticed about a half dozen dark brown marks. These areas were cut out, and the cross-sections revealed that only the very top layer of the coating was affected. This told us that the issue did not necessarily come from the roof underneath, and that it was probably not a product defect. If the product were contaminated, the issue would have been more widespread, and would have affected more than just the top layer.

When inspecting any roof, it is important to thoroughly walk the entire surface, not just the areas of concern. A serpentine pattern works well and allows the inspector to see all areas of the roof from multiple angles. We noticed about a half dozen dark brown marks.

The top layer of the coating was also separated from the other layers. One of the only ways this could happen with silicone would be from very high heat. A silicone roof coating is normally very resistant to heat and cold, with a minimum application temperature of 0 degrees Fahrenheit, and, once cured, can resist defects at temperatures exceeding 350 degrees Fahrenheit. We asked if there were any open flames or heating elements on the roof at any time. This was quickly ruled out as a possibility.

We then began to research the surrounding area for possibilities. This project was very close to a body of water, and, as we considered the time of year, a hypothesis was formed. Since we theorized that this damage must have been come from some kind of embers or hot coals, we researched what in the area might create these conditions. Then we wondered about fireworks.

We called the local municipality, and asked if there were Independence Day fireworks that were set off close to our project. We learned that they were actually set off less than a quarter of a mile from our location from a barge on the water. There was now a strong possibility that burning embers from aerial fireworks landed on our roof and caused damage.

There was now a strong possibility that burning embers from aerial fireworks landed on our roof and caused damage.

With a little searching on the Internet, we found an amateur video of that year’s fireworks being set off from the barge. Sure enough, through the explosions, our client’s glowing logo atop the building was visible directly beneath the trailing embers. We told the municipality of this, and they agreed to move the display a little further from land in the future, and our building owner agreed to keep an eye out for new burn marks after every July 4 celebration.

In this case, the integrity of the coating was never compromised, so a simple cleaning and light touch-up to the burned areas was an easy fix.

 

CASE NO. 3: THE STRANGE GOUGES

One of our experienced customers noted some unusual defects that they had never seen before during an annual inspection. The roof coating was 18 months old. The pictures made it clear that these were not product defects, but the cause of them stumped even the most experienced of our team.

A site visit was conducted, and many interesting issues were reported. First, these defects were widespread—almost every angle change, corner and even the field of the roof presented them. Some were small, some were large. Using a loupe, a close inspection of the defects helped us to determine that the defects were in fact many small scoop-shaped gouges strung together.

The pictures made it clear that these were not product defects, but the cause of them stumped even the most experienced of our team.

The widespread nature of the defects gave the impression that we were dealing with an animal of some kind. Was it a rat, snail, raccoon or bird? We began to look for clues as to what kind of animal we were dealing with. We saw evidence of all kinds of animals. We saw raccoon tracks, snail trails, bird tracks and curious scratch marks all over the roof.

One of the things we saw that helped us narrow it down was the presence of an overhanging oak tree, and gnawed acorns on the roof. The gnaw marks matched the scoop marks we noted on the silicone.

We also noted that there was heavy foliage and unkempt overgrowth along the backside of the building. We began to suspect that, while there was evidence of all kinds of wildlife on the roof surface, the animal that caused the damage was the same creature that was eating the acorns.

We began to look for clues as to what kind of animal we were dealing with. We saw evidence of all kinds of animals. We saw raccoon tracks (bottom), snail trails (top), bird tracks and curious scratch marks all over the roof.

The answers came to light once we inspected the overgrowth behind the building. We noticed little piles of acorns inside black plastic drainage pipes, and familiar-looking holes had been chewed into them. Further inspection led us to quite a number of frolicking chipmunks running along the pipes, acorns tucked in their jowls. Tiny bits of silicone were also found along the ground where the chipmunks were playing. Chipmunks are known for chewing rubber insulation or wires for bed fodder, and these chipmunks may have been using the silicone roof coating for that purpose.

In this case, we suggested the owner pay special attention to cleaning up the vegetative growth in the rear of the building. The presence of varied wildlife on the roof could present future issues, and removing their desire to live there is a humane and responsible way to deal with the problem. This roof required extensive touch-up and repair, along with landscaping to deal with the issue.

 

GUIDELINES FOR IMPROVEMENT

In conclusion, it is beneficial to note that, when issues arise, it is not always traceable back to negligence or even an honest mistake. Sometimes the variables in our world surprise us, and even the most experienced of professionals will run into issues that are completely new to them.

Proper training programs, which teach lessons learned over many years, have never been more necessary to help the roof coating industry grow in quality and success. Good communication between manufacturers, contractors and building owners help keep problems small, and—when problems inevitably present themselves—help create and implement the best solutions. Here are some easy to follow tips that will improve the process:

  • The contractor should keep a daily log. It should record things like ambient temperature, surface temperature, relative humidity and dew point. It should record applied wet-film thickness and dry-film thickness. It should also note any areas of concern.
  • The contractor should record the lot or batch numbers from their materials, along with the product name and color. Sometimes this is as easy as taking a picture of the product label.
  • The contractor and owner should agree to a maintenance program. This helps catch issues while they are small, and before they grow into what might be catastrophic and unrepairable.
  • A manufacturer’s representative and a trusted third party should help determine the cause of unexpected issues. Sometimes an objective perspective will help all parties see the problem more clearly.
  • Don’t forget to check things other than the roof surface. The underside of the roof deck or drop ceiling can reveal clues. Vegetative growth next to the building or overhanging trees might be part of the problem. Surrounding environmental issues like bodies of water, manufacturing emissions, heat sources or caustic substances may be to blame.

 

ABOUT THE AUTHOR

Fred Wolfe has spent the last 20 years in the roof coating industry. He has worked professionally in manufacturing, formulation, application and consultation. A NACE-certified coating inspector, he aspires to help usher in what he believes is the future of commercial roofing, namely liquid-applied coatings. He has a wife of 21 years and five children in Raleigh, North Carolina. He enjoys woodworking, fishing and target practice at the local firing ranges.

   

Tagged categories: Roofing contractors; Silicone

Comment from ROY CANNON, (4/13/2018, 9:03 AM)

Nice article which illustrates the many and varied calls coming into manufacturers of waterproofing and the challenges faced by technical personnel in sleuthing out the causes while maintaining product and supplier integrity. All too often the knee jerk reaction is to point to product deficiencies or defects when natural events and/or application issues are involved. One of the challenges for manufacturers is having the foresight to design products that will perform under unexpected events/conditions; easier said than done.


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